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Mitch Ware Member 
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Last year #19670 ran cool even on the hottest days. Then it was put away for the winter. Before taking it out of storage, I drained the anti-freeze and replaced it with a 50/50 mixture of distilled water and prestone green. I have noticed that the temperature guage has been reading higher on the average this year than it did last year (the first year that the car was back on the road). Yesterday, on a very warm day, the temp guage went right up to the red after about 3 miles. I nursed the car back home and let it idle in the driveway, spraying water on the front of the radiator. this brought the temp back down to where it has been reading since I took it out of storage this spring (just to the bad side of the middle). I checked the coolant level, it is fine. The thermostat seems to be opening since the radiator gets hot. The water seems to be circulating, since spraying water on the radiator cools the engine temp. The coolant level is where it is supposed to be. Both the radiator cap and the thermostat are one year old. The coolant is fresh. I blew out the radiator fins with compressed air to make sure the air was flowing, it is. I have had a shroud around the fan since I restored the car. So what gives? any ideas would be appreciated Mitch Ware 1974 JH-5 #111119670 1971 TR-6 #CC66950LO |
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Greg Fletcher Administrator 
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I would change the thermostat before I do anything else, as that sounds like an issue in this case. They can go bad anytime. You might look for one of those FailSafe thermostats- they fail in the open position and avoid the problems of sudden overheating that convensional thermostat can cause. |
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Judson Manning Member 
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Mitch, You might want to install an aftermaket water temp gauge. The stock water and fuel gauge run off a 9V regulator that is prone to failure resulting in higher temp readings when everything is actually fine. Judson |
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Mark Rosenbaum Member 
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Before changing the thermostat, I'd check two things: 1. Correctly operating temp gauge. With a coolant temp at a measured 80^ to 85^C (the normal operating temperature for the stock 82^C thermostat), the gauge should read mid-range or a needle's width to the right. However, as Judson notes, the actual reading depends greatly on the voltage stabilizer. (a) If the stabilizer fails in the 'always off' mode the temp gauge and fuel gauge will not work. (b) If the stabilizer fails in the 'always on' mode the temp gauge will appear to operate normally at first, but will rise to, or into, the red zone as soon as the engine reaches operating temperature; simultaneously, the fuel gauge will indicate far more fuel than is actually present (which is hard to detect if the tank is full). This seems to correlate with your car's symptoms. 2. Presence of coolant in the heater core -- air can be trapped there and later transfer to the engine, causing localized internal overheating. Your car is late enough that it may have a vacuum operated valve in the hose to the heater, and these are notoriously unreliable. Of course, as Greg notes, a thermostat can fail at any time and without warning. Worse yet, they sometimes fail intermittently and seriously confuse the issue. Last edited on 06-28-2005 01:22 am by Mark Rosenbaum |
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Mitch Ware Member
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My car does indeed have the vacuum operated heater valve. The fuel guage seems to be working accurately, but I will keep a closer eye on it. One of the things that puzzles me is how quickly the engine reaches operating temperature. According to the guage, it only takes about 1 mile of driving. Of course, it has been in the mid-90's here in upstate NY this weekend, so that may be a contributing factor. I went ahead and ordered a new thermostat and gasket, might as well try the easy fix first. As always, thanks for the suggestions and insight. Mitch Ware 1974 Jensen Healey JH5 #111119670 1971 Triumph TR6 #CC66950LO Last edited on 06-28-2005 07:20 pm by Mitch Ware |
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Mark Rosenbaum Member
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If I start my car when the air temp is 85^F, and let it idle on the driveway, it takes about seven minutes for the engine to reach the point where the thermostat opens -- in my case, a measured 185^F. This works out to a warmup rate of about 14^F per minute. It's my understanding that this is pretty typical of a 907 engine. So, if your car's temp gauge indicates overheating within a minute or two of starting from an overnight rest, I'd be very suspicious of the temp gauge. Of course, you could have a bad gauge (or voltage stabilizer), and a bad thermostat.... |
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Rory Clark Member
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I wanted to revisit this temp thing. Finally got my 73 on the road. (There are still things to do with Carb adj and recheck of timing) My car runs just a few points below the red line on temp ga. and stays there (50-miles of driving). I firmly believe it is running to hot So, what other things can cause the motor to run hot??? I know: 1) Thermostat 2) Air pocket in system. 3) Water pump 4) Others??? Rory |
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Jensen Healey Super Moderator 
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Running lean 2 core radiator sediment or corrosion in block bad valves clogged oil cooler wrong timing excessive antifreeze mix no fan shroud cheap plastic fan etc. etc. etc. In other words, Everything! Last edited on 10-16-2005 11:03 pm by Jensen Healey |
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Mitch Ware Member
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I eventually traced mine down to a failing voltage stabilizer. My fuel gauge and temperature gauge fluctuate in sync. It is on my list for things to address this winter when the car is in storage. Mitch Ware 1974 JH-5 #111119670 1971 TR-6 #CC66950LO |
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Judson Manning Member
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Actually, one thing we didn't mention is excessive blow-by. If your piston rings are shot, you'll have excessive oil temp which will cause the water temp to rise. The problem is similar to a blown head gasket where spent combustion gasses leak into the water jacket. However, a blown head gasket typically exhibits white smoke from the exhaust, as it's hard to keep pressurized water out of the combustion chamber during intake at idle (lots of vacuum). The excessive blow-by problem is hard to diagnose until you install an oil temp gauge. |
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Greg Fletcher Administrator
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Blow-by is unpleasant. I've experienced hotter temps with three cylinders that had marginal compression and one cylinder that was quite bad- the three were doing the work of all four. In that instance it was bad rings in the number four cylinder and was easy to see from the compression gauge since it was so far gone. Perhaps worth mentioning- the club store has been selling a lot of remanufactured water pumps and I've been noticing many of the cores I get back are not to spec- often the impellors are way off and not close enough to the housing. Whoever rebuilt the pumps last, didn't read the Lotus clearance recommendations in the manual. Some of these are so far off that they could conceivably effect the cooling (for the worse) on the engine, so you really need to look at everything at engine rebuild time or if you're getting a car recently that has issues. |
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Rory Clark Member
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One interesting thing that I have noticed is that the hose that runs on top of the motor to the thermostat is flattened when the car is cold once it gets up to temp and I assume the thermostat is open it goes to a full round. It is like as the motor cools down a vacuum is formed in the cooling system. Rory |
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Mark Rosenbaum Member
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Haven't noticed that sort of hose change in my car, either with the old hose or its replacment. Both were the Gates hoses that Delta provides, with the metal coil inside. I wonder if there's some relationship between what Rory reports and the (probably) defective hoses mentioned in the thread at the link below. http://www.jensenhealey.com/forums/view_topic.php?id=336&forum_id=3 |
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Rory Clark Member
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I will take a picture of it and post. With all the parts that I replaced, the hose are not among them. Now since the car is down for the blown exaust header gasket I guess I will order the hoses from Delta with the gasket. Rory 73-JH Here is the picture of the Flat Manifold Hose. Like I said once the car gets up to temp it takes the round shape Attachment: Rad hose flat.jpg (Downloaded 89 times) Last edited on 10-18-2005 04:05 pm by Rory Clark |
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LambandAndy Member 
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Well I drove 15223 to work today and actually arrived with the same amount of coolant that I left home with. For anyone buying a JH with unknown history I thought that I would relate some of our experience. After looking around for something a little more economical to drive than my 1977 F150 4X4 my wife suggested a Jensen Healey since I used to own one way back when. A search on the internet found a JH advertised on the JHPS website in South Carolina. A reverse look-up on the phone number showed it to be in Charleston, about 250 miles away. So after a couple of days and a couple of phone calls my wife, Lamb, and I piled on my trusty old Suzuki and headed for Charleston. The car was pretty much as the seller had told me and needed a new floor and a new top, but only had 40,000 miles on it. The title, issued in 1993, showed that the car had only covered ten miles in the last twelve years, so I believe this milage to be genuine. The seller also informed me that he had installed a new thermostat, new water temperature sender and had rebuilt the water pump. So a deal was struck and we set out for home, with Lamb driving the JH and me on the bike. Ten miles up the road Lamb pulls over with the temperature gauge in the red. Although indicating hot, the engine did not seem hot, not boiling and didn't have that 'hot smell'. So we let it cool down for a few minutes then carried on to the next gas station to investigate. After prodding around under the hood for a while I thought that maybe the guy had put neat antifreeze in, so drained some out and refilled with water. We were also getting very suspicious of the temp gauge. So we went on for a while and stopped at an auto parts store to see if they sold anything that we could verify the temperature with. After the third store we gave up on this but by then the car, and the day, had cooled off some. So to cut a long story short we made it home in fits and starts. Here are some of the cooling problems/corrective actions taken so far. 1. Installed correct thermostat (PO's new thermostat did not have the "bypass disc"). 2. Flushed cooling system. 3. Installed new hoses. 4. After reading e-mail on JHPS, noted fuel gauge and temp gauge reading high. Removed instrument panel and checked voltage stabilizer. Input was battery voltage and output seemed to fluctuate. Scratched head for a while, reassembled, and now fuel gauge and temp gauge seem to be working normally. (Bad connection?) 5. Removed piece of "spring" from previously installed flex hose from thermostat housing. 5. Removed water pump, pressed impeller on to correct clearance and reinstalled. 6. Removed radiator, re-soldered nipple for outlet to water pump and reinstalled. 7. Drove to work today and temp gauge remained at 3/4 scale. I am still suspicious of temp sender installed by PO. Infrared thermometer shows about 200F on the thermostat housing which seems about right to me. Is there a way to positively ID if this is the right sender? I cannot find any part numbers or Smith logo on it. Other work completed has been general engine tuning, changing of all fluids, correct installation of vacuum hoses (thanks Mark), replaced cam belt, replaced top (Bought a "cheapie" top from M & T Manufacturing for $177. I thought that it fitted well. Can put up pics if anyone is interested). Working on floor pan replacement. Thats it for now, Andy #15223 |
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John Finch Member
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Andy, I'd be interested in a pix and your opinion so far of the replacement top you purchased. Mine just ripped so I am forced into a replacement for spring driving in Minnesota. Thanks John |
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Harkes Member 
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Hi Rory, give us an update on how your car is doing now... Did you tackle the hot temp? The JH with decent compression and original 2 core radiator and original thermostat should be running in the middle of the temp. gauge and could go up when stuck in traffic. have you measure the actual temp whilst the temp gauge dial is up high? My old 2.0L engine ran fine eventhough it consumed quite a bit of oil!! You could indeed switch to a different (lower temp) thermostat and add water wetter to your cooling system. This is great stuff. Also check all hoses if there is nothing clogged inside. For instance my heater hose..the long thin hose that runs from heater box via bypass to the waterpump was fully closed up..!! not a good thing. Saw the picture of your manifold hose to the waterpump. I'd swap that one AND the upper and lower radiator hoses for the Gates hoses that are wire reinforced. They are only 15$ a piece at DMS. I'm most likely going for blue silicone wired reinforced hoses. they cope with heat very well, are very strong but mostly...look good. erik |
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LambandAndy Member
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Ok, so it looks like I crowed to soon. 15223 blew out coolant on the way home, but temp gauge never went over 3/4 (about 200F). My thinking is: Not overheating + blowing out coolant = blown head gasket (or worse) Anyone got any other ideas before I tear the head off? Andy #15223 |
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Rory Clark Member
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Eric, I have been to the Netherland many times what a beautiful Country (after you get out of Ampsterdam of course) My heat problem could be just a bad sender (but I do not think so) On a normal day here 29-35c it would just slowly climb to the 7/8 mark and stay there I could be driving at 55 or 110km (35-70mph) and it made no change. Bit Boy you open the hood and it sure seemed hot. Since I blew the exaust (Header Gasket) which is a no brainer to repair Just a super Pain in the A _ _. I did just as you said bought new upper/Lower hoses Plus the 74c thermostat (Jaguar PT# C28067). I have not installed hoses/thermostat (or fixed the Gasket) yet. But I will be VERY interested if this works on reducing the heat. Best Rory |
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Brett Gibson JH5 20497 Member
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Rory, getting back to your flattened hose when cold, it should'nt do that, so why is it, maybe the system becomes under vacumn, like when you fill a water bottle with warm water and then seal it and put it in the cold, you come back later and it all shrunk up, the only way your car can do that is if the Rad. cap doesnt allow the siphoning back from the overflow bottle. Just a thought.............. Brett. |
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Sander Member 
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Was that the yellow JH that had been owned by a doctor in Atlanta? |
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Rory Clark Member
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Brett, I thought that also. But I am getting some overflow into the bottle. What I do not know if it is going back into the radiator. The radiator opening is a little out of shape But...the cap appears to be operational thanks for the thought. Rory |
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LambandAndy Member
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Sander, Not sure if you were refering to me or not but the car looks to have been painted red a number of years ago but was originally mustard. Per Mr. Calvin the car was in Jacksonville, FL in the late seventies. Registered owner since 1993 was in Isle Palms, SC. I would be interested to find out any more history from the intervening years. Andy #15223 |
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Jensenman Member
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Rory Clark wrote: Brett, Be certain the cap is of the 'return' variety; some older caps would, like Brett says, allow coolant to escape when hot but not get drawn back in when cold, and that would definitely flatten the bypass hose as shown in your picture. Since the flat hose is due to 'vacuum' that tells me the main outer seals on the cap are okay. I'd replace the cap with a good quality 'return' style (has a flat brass disc on the bottom that's a one way valve). BTW, there were about twelve J-H's here in Charleston that I am aware of; a red and a BRG on the IOP, a dark blue one out toward West Ashley, mine, a friend of mine has one running and three parts cars, there was another one with a small block Chevy, same guy had a parts car. A guy left a note on my windshield with a Summerville number a while back wanting to sell me his, and there's the yellow one I missed several years ago. |
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Joseph Mazurk Member
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I have a question::: What is the oil gauge telling you when the water temp gauge reads past the 1/2 way mark??? I just installed a brand new Dave Bean water pump and a new thermostat and I am leaning just past the half way mark on the temp gauge but the oil pressure is reading about 40 lbs. when engine is warmed up. At first I thought it was the oil pump but when the engine first starts up I am getting 55 lbs of oil pressure. As it warms up and I am driving the oil pressure goes to 40-45 lbs. Any suggestions??? joseph mazurk chicago, il |
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John Finch Member
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Not quite sure of the meaning of your question but here goes. When the oil gets hot (warm engine) it thins out loosing its viscosity and the oil pressure drops as a result. When you start cold its thicker and you have higher oil pressure. 18309 starts at about 75psi at idle, after running and it gets really hot it will drop to about 35 at idle. My temp gauge is just to the right of center when the back of the thermostat housing is at 180 degrees fahrenheit. The JH manual says 60psi oil at 2500 rpm is normal. I've got about 75 at 2500 if the gauge is accurate. Not sure if this answeres your question. Hope it helps. John |
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Joseph Mazurk Member
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Hi John, Thanks for the reply. I know about viscosity and how it changes when the engine is warm. My engine just started to read 40-45 lbs of oil pressure at 4000 RPMs doing about 70 MPH. Before it was always reading at 55 lbs doing these numbers. I feel very comfortable when my engine reads below 50 lbs. at 70 MPH. I worry that it is the beginning of problems. On a side note I did a compression test and got 125, 130, 130 and 130 with 89,000 miles on the speedo. When the engine starts the oil pressure is at 65 lbs. and when warm does the nose dive to 40-45 after driving it for about 15 minutes. I think this rules out a bad oil pump. So far I am at a loss for a explanation as to why the oil readings are so low. I also disconnected the oil line from the engine and installed a new oil line to a spare oil gauge and got the same numbers. I will check the ratio of water to coolant and add Water Wetter to the coolant. Joseph Mazurk Chicago, IL |
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Joseph Mazurk Member
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Oops, I should have said "I feel very uncomfortable when..." Joe |
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John Finch Member
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Hi Joe, I don't know enough about our engines to go much further other than to agree with you that you might want to stay on top of your oil pump. Is your oil cooler installed? I also run watter wetter and just added water pump lubricant to the coolant as well just to be safe. I hope I didn't offend with the viscosity thought. It was not my intention at any rate. Try one of the Lotus forums. There might be some info there. Piston Heads and Golden Gate Lotus Owners are sites I go to sometimes. Best of luck John |
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Jensen Healey Super Moderator
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Hi Joe, So you're saying that the installation of the water pump lowered your oil pressure? It's possible that the new water pump isn't flowing as much water as the old one but that should show up on the gauge. You may have had a coincidental clogging of the oil filter or oil cooler. Have you changed the oil and filter? Does your pressure go up to 50 lbs at 5000 rpm? If so you are within the Rosenbaum parameter of 10 lbs for every 1000 rpm and should be OK for normal driving. I hope it's not a sign of worn bearings. Kurt JH 13148 |
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Joseph Mazurk Member
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Hi Kurt, Could be a clogged oil cooler. This is something I suspect. The fact remains the same, my oil pressure has never ever gone below 50 lbs. at any speed and at any temperature. I might have to take the oil pump off and do Greg's solution to his sudden drop in oil opressure and that is check oil relief valve in the oil pump. Thing is the Eastern J2006 is coming up quick (June 7-10) and I need a solution quick. I do have several oil pumps to switch to if I need to, so I will keep the message board apprised of my progress. Please say a big prayer that it isn't the bearings. Have fun this weekend!!! Joseph Mazurk |
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dciaccio Member
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Joe & All: My '73 #12248 is in the same condition. The engine temp seems to run up to about the 3/4 point on the gauge or slightly above when the outdoor temp is around 85 degrees and above. Cooler days its just fine. I only have two core radiator which I had cleaned by a local radiator shop. As it seems now from reading all the posts, I probably should have had a three core put in. Joe, my oil pressure is the same. best it will do is about 50-55 psi at cold start but drops to 40-45 psi at 3000rpm when hot. at idle its sitting down around 20-25 psi...little scary. Right now I am more concerned with the higher engine temp. Is it the groups advice to go with the 3 core rebuild ? Any other final checks I should run before spending these dollars? Thanks Dave Ciaccio '73 JH #12248 |
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Mark Rosenbaum Member
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Dave: Your oil pressure at cold start is a bit lower than normal but seems better than average when hot. If your oil gauge is accurate, you might wish to address the oil pressure relief valve if you ever have need to open up the oil pump, but other than that, I wouldn't be concerned. For the temperature issue, you might wish to consider the possibility that your dash gauge is less than absolutely accurate. Before spending lots of money to fix a problem that may not exist, it would be prudent to actually measure the coolant temperature with a real thermometer. If your cooling system is in good shape it will keep the coolant at the thermostat's rated temperature, or 100°F above the local air temperature, whichever is greater, under normal street driving conditions. For more aggressive driving, this temperature difference will increase significantly, but that isn't a problem unless the coolant starts to boil. If the antifreeze mix and radiator cap pressure are correct, boiling won't occur until the coolant temp exceeds 238°F or thereabouts. That said, if the cooling system is not performing as expected, you may wish to check the following areas (some of which have been mentioned by others on this thread):
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dciaccio Member
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Joe: I am in the same situation. At start up I get about 50 psi. As the temp gauge climbs up to normal, it drops a bit to 45 psi. As the temp climbs up to the 3/4 point but under the redline, my oil pressure is about 40 psi at 3000 rpm. I am open to eveyones thoughts here too. Sounds like I am within Mark's tolerable limits of 10 psi /1000 rpm. Makes me feel a little better. Thanks. Dave Ciaccio Omaha, NE JH #12248 |
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mdutch Member 
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Okay, so any sources for a new Voltage stabilizer for the metering? |
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mdutch Member
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Thanks for the reply. I know about viscosity and how it changes when the engine is warm. My engine just started to read 40-45 lbs of oil pressure at 4000 RPMs doing about 70 MPH. [...] Joseph Mazurk Joe, I had a similar problem for a while until I was informed that "modern synthetic oil" is too thin when hot to maintain proper pressure. Use good old fashioned Castrol I believe was the consensus. Once I changed the oil from 10w30 Mobil 1 to 30w Castrol, the pressure was normal. Last edited on 08-23-2006 05:08 pm by mdutch |
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flatlanderep Member 
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Judson Manning wrote: Mitch, Judson, I suspect my '73 JH is suffering from this problem as a new thermostat was just installed but the temp gauge is fluctuating like crazy....One minute it's at the 3/4 mark and then the next its barely registering at the 1/4 mark. Is there a way to test the regulator to verify that it is indeed that, rather than something else? Thanks, Paul |
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Jim Sohl Member
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The address below is to the Lotus Club of N.Y., N.J. If the address doesn't work, the newsletter is May, 2004. Anyway, the article is about a solid state 'voltage stabilizer' and it appears to be worth a second look. I have not tried the system out as yet, but it sure looks more promising than the original Smith unit. Cheers, Jim http://www.lotusenthusiasts.org/Newsletter/V5-10.pdf |
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John Finch Member
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I bought one in Oct 2005 from Edgar Esslinger at esslinger@charter.net on ebay for $20.00. Works great so far. It was listed as a Triumph TR4 Solid State Gauge Regulator on ebay. Try an ebay search. Also, Ed's seller ID on ebay is coolsunbeam Good luck John |
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dwalls1 Member
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FWIW Dept. Since Greg et al convinced me that the temp gauge should never get over 1/2 even after prolonged idle, I've bought and installed the fan shroud. It seems to be the ticket as I can leave the car idle for a long time now and the temp shows just barely over 1/2. The install was not too straight forward even when done in conjunction with the cam belt replacement as I had to have the crank pulley machined off to clear the fan after removing the spacer from behind the fan. (all this is residue from the A/C removal) All in all I'm glad I've got the fan shroud and it looks pretty cool to boot. |
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