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| Water Temperature Gauge Calibration | Rate Topic |
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| Posted: 08-16-2017 07:12 pm |
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1st Post |
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DonBurns Member
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Has anyone calibrated their stock water gauge to determine what temperature relates to a given position? I have been working with a possible running hot situation, and am now a little suspicious of the actual gauge. This is a fresh rebuild to a 2.2, 9.6 CR, new 3-row radiator (Aluminum), new larger oil cooler, electric fan added (on front, pushing rear), fan shroud and replaced the sender. I had the engine rebuilt by a machine shop and I'm pretty confident they cleaned the block - as near as I could determine from inspecting it before assembly anyway. So really should not run hot. I went to a 160 thermostat. The gauge goes to the center of the range quickly, then slowly climbs to just under red. It has never actually overheated. I am suspicious of the gauge because I searched on the forums, and found the previous owner of 15800 posed in 2011 that the car ran hot. There is pretty much nothing left of the original engine after this rebuild, so that seems strange. Today I took the sender and soldered a ground to the side, extended the lead wire and dropped the sender into a flask of boiling water with a reference thermometer and watched the gauge. I left the gauge in the car and ran the engine so the voltage would be the same. The point just below red where my car wants to run turned out to be 200F, and the center of the gauge turned out to be 160F. Is this what it should be, or is the scale shifted up? 160F seems kind of low for a target running temperature. I am in California, so ambient of about 80-90. I have seen posts suggesting normal running temperatures of 180F. But this seems to not match my experiences with a hot radiator. Boiling temperature for 50:50 antifreeze is over 230F, and something higher than that under pressure. With a hot car just parked, I think everone has learned to not open that radiator cap for awhile, and not just a JH but a modern car with the temp gauge showing below center. If the water was at 180F, I would not expect to blister my hand (should I ever be so foolish) so I have assumed typical temperatures in the cooling system were much higher. I believe some have replaced the Lucas gauge with modern digital gauges. What temperatures do people really run at?
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| Posted: 08-16-2017 08:00 pm |
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2nd Post |
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redracer Member
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Don: both the water and fuel gauge run off a 9 volt stabilizer attached to the metal gauge plate with a sheet metal screw(above the 2 gauges in the back) This screw acts as the ground connection for the gauges and is notorious for oxidizing causing a full 12 volts to both gauges. The 12 volts will move the gauges 22 1/2 degrees CCW (counter clockwise) giving a false "hot" reading. The 2 little white dots at the bottom of your temp gauge are supposed to be 180 & 185. Removing the sheet metal screw and cleaning both the ground connection as well as the small section where the copper tab protudes onto the casing should help. Hope this helps, bruce
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| Posted: 08-16-2017 08:24 pm |
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3rd Post |
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DonBurns Member
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Thanks Bruce - So if 180-185 is normal in pre-global warming England, I assume 200 in So Cal is probably not out of line?
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| Posted: 08-16-2017 08:39 pm |
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4th Post |
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redracer Member
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Assume you got one of the CHAMPION 3 row jobs? I never used one(mine and many others used 4 rows in with the original "tanks") but have heard good things about them. So, did you check the voltage at the gauge itself? 200 would still be too high in my opinion unless you were absolutely stalled in traffic or there was something wrong with your pump, although I've never seen that problem with the pump; usually the bearing get "wobbly" or the original style has the seal rupture.
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| Posted: 08-16-2017 09:04 pm |
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5th Post |
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DonBurns Member
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Champion 3-row, correct. This car came with a non-original radiator (narrow and long - couldn't even get a jack under it) so I didn't have a core to rebuild. I am heading out on a trip, will look at the voltage regulator this weekend. Already let Greg know I would probably be sending the water pump in for exchange. It looked good so I didn't replace, but it is the only thing left that is original.
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| Posted: 08-16-2017 09:09 pm |
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6th Post |
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redracer Member
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Having rebuilt well over 300, again, they are usually fine if not leaking; at least check the bearings by grabbing the fan blades and gently rock to see if there's much play; adjust belt to just barely tight when the engine is hot/warm.
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| Posted: 08-17-2017 08:08 pm |
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7th Post |
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Esprit2 Member
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The engine needs to come up to normal operating temperture to run right, and to prevent moisture condensation build-up inside the engine. There is such thing as too cool. The thermostat's rated temperature is the point at which it starts to open, and the engine will normally run a little hotter than that. 85C (185F) is low-normal, IMHO. 90C (194F) is pretty normal. 105C (221F) isn't going to do any short term damage, but if your engine makes a habit of running that hot, you should find out why and address the cause before it becomes a problem. The JH 907's water pump has a pretty pathetic little impeller that's prone to cavitation. The later Lotus 907 impeller is an improvement, but still underwhelming. Installing a 910 Turbo water pump's impeller is the best hop-up you can give your otherwise stock pump. The 910 impeller is taller, and won't fit in the JH housing. Just have a machine shop shorten it's nose to the same overall length as the JH impeller, and the rest of the rebuild procedure goes as before. The 910 pump, and the Federal Esprit's 907 pump use a smaller 4.5" diameter pulley (verses 5.25") to spin the pump faster and increase circulation. But the two pulleys have different bolt patterns, and therefore require different hubs on the pump. Changing pulley sizes is a decision to make when the pump is apart for a rebuild. I strongly recommend the 910 impeller and 4.5" pulley for all 9XX engines operating in hot climates. The majority of my 907 overheating issues have been gauge related, including the sender and voltage stabilizer... mostly the stabilizer. When it fails, or it's ground connection corrodes/ loses continuity, then the voltage goes high and all the gauges it feeds read high. The temp gauge for sure. Regards, Tim Engel
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| Posted: 08-20-2017 11:44 pm |
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8th Post |
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DonBurns Member
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Tim- Thanks. Are 910 water pumps something that are available without a rebuildable 910 core? Based on my calibration effort I now believe my car is not really overheating at all - just a voltage stabilizer or gauge issue. I ordered a new voltage stabilizer from an EBay vendor - listed as "Jensen Healey Land Rover Lotus Elan Europa & MGB GT Alternator Voltage Regulator". It is stamped with Lucas 12V. I'm not sure it is the right thing as it made no difference at all and may be a stabilizer to stabilize at 12V, not 9V. I should have benched tested before installing but will do this next weekend. Getting the stabilizer in and out is not the easiest thing and requires getting the cluster out, and is difficult if you are not as flexible a you used to be. -Don
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| Posted: 08-21-2017 12:27 am |
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9th Post |
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redracer Member
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Don: have quite a few used ones; I'll have to bench yest them first but I advise you do that to yours first. Getting at/to the stablilizer is not all that difficult if you're not huge. I'm not small but I'm not a "load" so by putting the seat all the way Back and slithering under the dash upside down with a #2 cross point/pozidrive bit, you could undo the stabilizer, but first I'd take a VOM under there and see if in fact you are getting 9V output and not the errored 12V.
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| Posted: 08-21-2017 12:50 am |
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10th Post |
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DonBurns Member
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There may be different ways to attach the stabilizer. Mine was attached between and above the temperature and fuel gauges. Being above there seemed to be no way to reach without removing the instrument cluster. Mine was attached with a standard Philips screw, so I guess may not have been in original position. I have a new wiring harness but am holding off installing until all issues are addressed and I take to paint and body which will be a strip to bare metal job, so interior will be out anyway. Hope to address various issues like this then.
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| Posted: 08-22-2017 12:53 am |
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11th Post |
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DonBurns Member
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OK - I got the new stabilizer out and bench tested. The output voltage was still 12 volts. The new EBay one had two wires, with nothing to indicate a 12 volt input wire and 9 V output wire. Does it matter? If it does matter, is the stabilizer damaged if you attach the 12 volt supply to the wrong side? I have ordered one from Delta, and will get tomorrow. Now that I have modified the wiring harness to use with the new stabilizer, I don't remember which wire was which. On the original stabilizer there is a double male connector and a double female connector. Can someone verify which the dark green (12 Volts in) connects to, and the light green voltage out goes to? Sometime during all this pulling the dash apart, the little insulator attached ended up on the floor. Does anybody recognize it? I thought it might have come from the stalk switch (turn signals, wipers etc.) but I don't see where it could have come from, and all of the functions seem to still be working. Thanks Attachment: Insulator.jpg (Downloaded 93 times) Last edited on 08-22-2017 04:23 am by DonBurns |
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| Posted: 08-22-2017 01:00 pm |
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12th Post |
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Rick in Miami Member
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Dark green goes to the male connector. The stabilizer case must be grounded for it to work correctly.
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| Posted: 08-22-2017 01:55 pm |
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13th Post |
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DonBurns Member
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Rick- Thanks for the help. The ground to this seemed a little iffy so I added a ground wire from the mounting screw to one of the gauge grounds.
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| Posted: 08-22-2017 03:35 pm |
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14th Post |
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Esprit2 Member
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DonBurns wrote:Thanks. Are 910 water pumps something that are available without a rebuildable 910 core?Sorry about being so slow getting back to you. It really helps to have a core. No new 9XX pumps have been manufactured in a long time, so it's just a matter of rebuilding available cores. The problem is that 'nobody' bothers to return their cores for a refund. It's like no one understands just how shallow that pond really is. Even if you find a rebuilt pump available for which the seller doesn't require a core (try Lotusbits in the UK), it would be great for everyone if you kept your 907 core in in the loop. It won't help the 910 supply, but it will help 9XX pump supply overall. But I'm not recommending that you install a 910 pump. It has additional hose spigots the JH doesn't use, and it points some of it's hoses in different directions. It bolts directly to the block, but some of the external plumbing would require creativity. That's possible, I've done it, but it's less of a hassle to simply install the 910 impeller in the stock pump housing. IMHO. True, the tall 910 impeller needs to be machined down to 907 height (just shorten the nose), but the rest of the rebuild procedure is the same. Regards, Tim Engel
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| Posted: 08-23-2017 12:42 am |
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15th Post |
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Esprit2 Member
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The JPEG compares the later Lotus 907 impeller with backward curved vanes (on the right), with the 910 impeller with the full-length, backward curved vanes. The dimension given for the short, right impeller applies to the Lotus impeller, and I can't say with certainty the JH impeller is also that height. The point is to take the old impeller from the pump and the new 910 impeller to a machine shop and have them shorten the tall 910 to match whatever the original impeller. Be sure they put a small chamfer in the upper end of the bore to make it easier to press the bearing shaft into the impeller. Regards, Tim Engel Attachment: Cooling - Water Pump - Impeller - 907 left & 910 right - side, Notes.jpg (Downloaded 83 times)
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| Posted: 08-23-2017 01:02 am |
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16th Post |
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redracer Member
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Don: If you do get a 910 impeller, you can cut it down as much as you wish even with a grinder if you use the 3G seals, as they do not need the nose of the impeller to compress the seal, which is nicely made into a one piece unit--nice. I/we have never had the need to use a 910 impeller, and I assume from Tim's writing that it has the same I.D. as the 907 ones. But if you happen to get one, be sure to get a 3G seal to go with it. bruce
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| Posted: 08-23-2017 04:13 am |
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17th Post |
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DonBurns Member
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Thanks Tim and Bruce- I am hoping my issue is just a defective voltage stabilizer, and I have no overheating issue to fix, so no reason to improve the pump. I'm still struggling to determine this though. I have a reliable 12V power supply that I use to power a 12VDC pump, and a Fluke 77 multimeter I can trust. I have been testing the voltage stabilizers by attaching the positive lead of the power supply to the hopefully correct lead of the stabilizer and clip the negative lead to the stabilizer housing. Then attach the positive lead of the Fluke to the stabilizer output and hold the other to the stabilizer housing. With the original stabilizer I get erratic readings - bounces around overload, 12, 10, 0 and won't stabilize. I sanded the housing for the ground contact, and cleaned the contacts with spray electrical contact cleaner and q-tipped, with no change. The second stabilizer from EBay gave me 12VDC in and 12VDC out. I just receive one from Delta (complete with diagram showing which leads were 12V in and which 10V out). When I checked as described above, I get a very consistent output of 0.34. I'm either doing something wrong or I'm extremely unlucky. Someday I'll document this entire restoration and you'll suspect the latter. Started with the transporter dropping the car off the trailer, and has gotten worse since then. BTW - the documentation that came with the stabilizer from Delta says the water temp and fuel gauges are set for 10V, not 9V. Not saying that is right or wrong - that's just what came with the instructions. In case a better pump turns out to be necessary however, are the impellers and seals available? From where? Last edited on 08-23-2017 05:03 am by DonBurns |
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| Posted: 08-23-2017 05:41 am |
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18th Post |
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answerman Member
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Don, before you go any farther (assuming you haven't done this yet, though I read through everything kind of fast so maybe I missed it) have you checked the temperature with a different instrument? I did see that you have a Fluke 77 (my meter of choice also) which doesn't allow for temperature measurement, but there are a lot of other ways you can test. Infrared thermometers are pretty cheap, or even a digital meat thermometer like the one I use to check my steaks for doneness. Just an idea. BTW, you are right: the output from the voltage stabilizer is indeed 10V, which is the correct voltage for the Smiths gauges.
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| Posted: 08-23-2017 12:50 pm |
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19th Post |
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Rick in Miami Member
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'With the original stabilizer I get erratic readings - bounces around overload, 12, 10, 0 and won't stabilize.' Don, that is what it is supposed to do. The bi-metal strip in the stabilizer heats and cools to provide the average 10v output.
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| Posted: 08-27-2017 12:26 am |
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20th Post |
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DonBurns Member
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I believe I have finally come to a resolution of this - but it was painful. Answerman- What led me to finally question the voltage stabilizer was when I measured the block temperature with an IR thermometer, and it was only reading in the 180 - 190 range. I didn't fully trust that so I took my spare sender and put it in hot water with a good digital thermometer and found that the center of the meter was 160F (should be about 180 - 185). Rick - thanks - I would never have expected that. The stabilizers from EBay and Delta did not do that - they just gave steady voltage outputs that were wrong. Here is where it gets messed up. It was recommended to make sure the stabilizer was properly grounded. Since it took some effort to get to, and they are not expensive, I decided to get a new one from Delta Motorsports and make sure it was grounded. I bench tested it first and got the .35 V output, so was suspect of this. Today I realized I had never tested the original with a proper ground, and when I did, again outside the car with hot water, it gave the correct gauge reading with 180F at the first small dot. Since I had not tested the new unit from Delta in the car, I swapped that in to test. This is two minutes later. So when I turn the ignition key, the starter doesn't turn. All other electrical OK. After four hours trying to figure out what I messed up under the dash with all of this taking apart and putting together, verifying the starter switch still works, tracing the white / red wire through the seat belt switch and relay, and basically going nuts, found that the female side connector within the 5-position connector in the engine compartment had worked loose. BTW -the Delta unit acts just like it is putting out .35 V. No movement of the water or fuel gauges. Thanks for the support - this is a big deal as I have been trying to figure out the "overheating" for nearly two years. Apparently so was the previous owner in 2011.
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