Lotus Elise SC: Anyone Changed the Thermostat? - Page 3 - LotusTalk - The Lotus Cars Community
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post #41 of 63 (permalink) Old 11-26-2017, 06:54 AM
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One question for all you guys saying it's air in the system.....how did it get there after 1.5 years (roughly)? I'd assume (and maybe I'm being naive) that *eventually*, any air in the system is going to work it's way back up to the reservoir and out through the overflow tube. Is that not the case?
The reason there are bleeders in cooling systems at certain points is because air or vapor can get trapped at a local high point (like an upside down U in a line that continues below that point)... the result is that the system may not self-bleed there, so you have to do it manually.

Assuming you started with a properly bled system, one way to get air into the system would be to start the engine, get it very hot, then shut it down and let it heat soak (sit with no further active cooling). Coolant sitting in the very hot head could boil, turn to vapor and push coolant into the overflow tank. If you remove the radiator cap before things cool down sufficiently, atmospheric pressure is insufficient to collapse the area filled with steam back to liquid (it could end up sucking air through the open radiator cap instead of coolant from the expansion tank). On the next startup, you have a void in the cooling system not filled with coolant. This lets the head get even hotter on the next start up, creates more steam, dumps more coolant into the expansion tank and potentially even out an overflow if the expansion is sufficient.

I’m sure there are other ways for this to happen. For example, the constituents of coolant break down into their component gasses (hydrogen, oxygen, etc.) when heated many times. Expansion tanks and swirl pots are usually sufficient to remove the resulting small gas bubbles in the system. But if a cooling system were operated for short periods, it is conceivable the normal course of events - the bubbles get removed - could be circumvented. The bubbles would then migrate to high points in the cooling system and create voids in the coolant. The chemical reaction of coolant with metals can also create gasses. For the record, although this mechanism is possible, it seems less likely to me.

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Last edited by Glen; 11-26-2017 at 12:40 PM. Reason: Correct first sentence and add example
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post #42 of 63 (permalink) Old 11-27-2017, 08:30 AM
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One question for all you guys saying it's air in the system.....how did it get there after 1.5 years (roughly)? I'd assume (and maybe I'm being naive) that *eventually*, any air in the system is going to work it's way back up to the reservoir and out through the overflow tube. Is that not the case?
Judging by the amount of trouble people have getting the air out, that may not be the case. Glen suggested a steep hill. Perhaps jacking the rear of the car would help. My Elise's nose will hit the cement though, so I have to put the front wheels on a couple of 2x4s to get the rear end up to the full jack height.
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post #43 of 63 (permalink) Old 11-28-2017, 05:41 AM Thread Starter
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Judging by the amount of trouble people have getting the air out, that may not be the case. Glen suggested a steep hill. Perhaps jacking the rear of the car would help. My Elise's nose will hit the cement though, so I have to put the front wheels on a couple of 2x4s to get the rear end up to the full jack height.
Everytime I've bled the system in the past, I've done it with the rear end elevated until the front splitter area is about to touch. Don't know if it helps or not to be honest.
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post #44 of 63 (permalink) Old 12-03-2017, 01:14 PM Thread Starter
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Another question: Anyone know if the oil dipstick tube is simply a push-in with a rubber o-ring or grommet on the engine block?

The way the factory designed this on the SC model is a royal PITA. They have a steel tab welded to the oil dipstick tube that affixes the tube to the block at the uppermost stud/bolt for the t-stat housing. Since the nose cone of the SC effectively encases the dipstick between it and the rest of the engine, you can't wiggle it to get it off the stud. I ended up having to bend it out of the way with pliers. I'd like to remove it from the block and straighten that tab out (wasn't able to just use pliers again to straighten it), but I'm not sure how it's held on at the block/pan junction.

Anyone know for sure? I definitely don't want to just yank on it and risk breaking something that isn't a push-in....

TIA,
Sean
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post #45 of 63 (permalink) Old 12-03-2017, 01:47 PM
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Another question: Anyone know if the oil dipstick tube is simply a push-in with a rubber o-ring or grommet on the engine block?

The way the factory designed this on the SC model is a royal PITA. They have a steel tab welded to the oil dipstick tube that affixes the tube to the block at the uppermost stud/bolt for the t-stat housing. Since the nose cone of the SC effectively encases the dipstick between it and the rest of the engine, you can't wiggle it to get it off the stud. I ended up having to bend it out of the way with pliers. I'd like to remove it from the block and straighten that tab out (wasn't able to just use pliers again to straighten it), but I'm not sure how it's held on at the block/pan junction.

Anyone know for sure? I definitely don't want to just yank on it and risk breaking something that isn't a push-in....

TIA,
Sean
FWIW

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post #46 of 63 (permalink) Old 12-03-2017, 03:11 PM Thread Starter
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Just fired it up after changing the t-stat. A total of just under a gallon of fluid came out due to the T-stat change. Replaced about that amount of fluid before starting up. Ran until temp reached 212F, then shut down....fan never came on and the radiator never got hot. Bleeder was open at the front passenger wheel well, hose wasn't hot....small amount of bubbles came out initially, then stopped. Rear bleeder in the engine bay was open....no bubbles, just fluid. Heater was in the "on" position with fan speed at highest setting on the interior.

After shutting it off, I pressure tested system. Under 15 psi, the front bleeder had a steady stream of fluid coming out. Rear bleeder initially didn't leak....but I tightened it a bit more (after noticing earlier that it's not an o-ring, but a flat rubber disc...that may used to have been an o-ring)....and it started leaking. Need to replaced that flat rubber disc with an o-ring before I can check anything else.

Is the reservoir tank supposed to be capped while attempting to bleed the system with the car running? I've never had to do that before on a regular radiator with a normal overflow tank. What about that little bleeder on the reservoir itself....supposed to be cracked or tight?
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post #47 of 63 (permalink) Old 12-03-2017, 03:15 PM Thread Starter
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Thanks....it's just an o-ring then. Much appreciated!
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post #48 of 63 (permalink) Old 12-03-2017, 03:28 PM
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Thanks....it's just an o-ring then. Much appreciated!
You're welcome.

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post #49 of 63 (permalink) Old 12-04-2017, 11:53 AM
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Just fired it up after changing the t-stat. A total of just under a gallon of fluid came out due to the T-stat change. Replaced about that amount of fluid before starting up. Ran until temp reached 212F, then shut down....fan never came on and the radiator never got hot.
How long did it take to hit 212F?
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post #50 of 63 (permalink) Old 12-04-2017, 07:31 PM Thread Starter
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How long did it take to hit 212F?
Not very....sorry...can't quantify exactly. A few minutes. Once I got a temp reading it climbed pretty steadily. I'd say once I got the 158F reading....it was 5-7 minutes at most.



On another note, basically filled the reservoir this morning before leaving for work, it had apparently burped a little overnight. It didn't take much fluid, maybe a 1/8 gallon or so. Came home tonight after getting a new o-ring for the rear bleeder. Pressurized the system and got a fair amount of fluid out of the front bleeder and made sure the rear bleeder's new o-ring was sealing. Tightened both up just to see if it would hold. It held 15 psi for 10 minutes or so....then I went inside and did some chores....came back out another 40 minutes later...it had dropped to 5 psi. Decided to start it up, get the engine warm and see if I could get it to burp again and so I could check the radiator, etc.

Ran it for a good half hour.....very slowly climbed to 195F. Ran it with the heater and with the A/C. No real change between those two. Radiator was hot on the driver side and cool on the passenger. The fans never kicked on, but I seem to recall that they only kick on if the A/C is on and the temp gets over 195 or 200-something. Need to look it up. Reservoir started to foam and spill as it got up around 180 so I put the cap on it. I'm letting it cool down now and will mess with it more in the morning.
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post #51 of 63 (permalink) Old 12-05-2017, 05:55 AM
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...
The fans never kicked on, but I seem to recall that they only kick on if the A/C is on and the temp gets over 195 or 200-something. Need to look it up. Reservoir started to foam and spill as it got up around 180 so I put the cap on it.
...
I posted info about temps for you in this thread here. Once you’ve bled the cooling system, testing should be conducted with the expansion tank cap on. The cooling system is designed to operate pressurized.

You’ve mentioned the heater several times . . . unlike many other vehicles, coolant always flows through the Elise/Exige heater core. When you select heat, all you’re doing is opening a flap to admit warm air into the cabin. So there’s no need to select heat while bleeding the cooling system.

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Last edited by Glen; 12-05-2017 at 06:01 AM.
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post #52 of 63 (permalink) Old 12-05-2017, 06:14 PM Thread Starter
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I posted info about temps for you in this thread here. Once youve bled the cooling system, testing should be conducted with the expansion tank cap on. The cooling system is designed to operate pressurized.

Youve mentioned the heater several times . . . unlike many other vehicles, coolant always flows through the Elise/Exige heater core. When you select heat, all youre doing is opening a flap to admit warm air into the cabin. So theres no need to select heat while bleeding the cooling system.

Glen
Thanks Glen!
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post #53 of 63 (permalink) Old 12-05-2017, 07:32 PM Thread Starter
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Ran for 50 minutes....got to 208F, fan kicked on (low speed)....dropped temp to 201. It's only 52 ambient here tonight. Doesn't seem like it should be running that hot....not confidence inspiring when the temps hit 110-115F. FYI....these notes are mainly for me. If anyone has advice, feel free to chime in though.
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post #54 of 63 (permalink) Old 12-05-2017, 08:38 PM
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@Sean K. - I think you are trying to infer how the cooling system in your Lotus will perform during normal use from how it performs at an extended idle. The amount of heat generated and the amount of airflow across the radiator are massively different under these two conditions.

The design intent of the cooling system in your Lotus is to get the engine up to operating temperature as quickly as possible, then keep the temperature in an acceptable range under the expected operating conditions. The engineers only intend that your vehicle will survive an extended idle with no airflow generated by vehicle motion . . . they did not intend that it would achieve and maintain an optimal temperature.

Have you ever seen a vehicle on a dynamometer and wondered why they had big fans pointed at the radiator? It’s because the built-in radiator fans alone can’t move enough air to maintain an acceptable operating temperature. Your vehicle is designed to be in motion and that’s the environment for which the cooling system is designed. So if you want to conduct a meaningful test of your cooling system, you need to go drive your vehicle and subject it to the conditions you want to survive. A properly operating thermostat will largely negate the effect ambient air temperature has on coolant temperature. Yes, even in Arizona.

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Last edited by Glen; 12-06-2017 at 04:50 AM.
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post #55 of 63 (permalink) Old 12-06-2017, 05:24 AM Thread Starter
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@Sean K. - I think you are trying to infer how the cooling system in your Lotus will perform during normal use from how it performs at an extended idle. The amount of heat generated and the amount of airflow across the radiator are massively different under these two conditions.

The design intent of the cooling system in your Lotus is to get the engine up to operating temperature as quickly as possible, then keep the temperature in an acceptable range under the expected operating conditions. The engineers only intend that your vehicle will survive an extended idle with no airflow generated by vehicle motion . . . they did not intend that it would achieve and maintain an optimal temperature.

Have you ever seen a vehicle on a dynamometer and wondered why they had big fans pointed at the radiator? Its because the built-in radiator fans alone cant move enough air to maintain an acceptable operating temperature. Your vehicle is designed to be in motion and thats the environment for which the cooling system is designed. So if you want to conduct a meaningful test of your cooling system, you need to go drive your vehicle and subject it to the conditions you want to survive. A properly operating thermostat will largely negate the effect ambient air temperature has on coolant temperature. Yes, even in Arizona.

Glen
I understand that....however, at this point, I'm just trying to ensure all the air is out of the system and that there are no leaks....

The pressure tester is not holding pressure though...indicating there is a leak somewhere, but I'm not losing fluid....which makes me wonder if it's the tank or the tester itself not sealing (or the seals in the tester, etc).

The other problem is though....with traffic being what it is here, extended idling where you don't move at all or not above 1st gear is all too common. It is that type of scenario that's seen the temp spike up above that 226 point in the past and keeps me from taking the car out much due to the possibility of overheating. In short, I don't trust it and in it's current state of repair, I'd say it's still not ready for that type of use.

My work schedule is currently such that I don't have time to dedicate to it the way I'd like so I'm working in spurts. I'll likely try the airlift on it next as something still seems off.
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post #56 of 63 (permalink) Old 12-06-2017, 08:16 AM
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No comment about your issue. But I am reading along and am enjoying the detailed advice being offered.
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post #57 of 63 (permalink) Old 12-06-2017, 08:32 AM
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If the coolant is being circulated, the fans at low speed are enough to keep idle cool on the hottest of days. You shouldn't see above 208F unless there is a problem. You are almost guaranteed to see 207 though unless you are running AC, at which point the temp should be lower since the fans are always at least low speed.

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post #58 of 63 (permalink) Old 12-06-2017, 07:27 PM Thread Starter
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So tonight I went to pressure test it....and couldn't build any pressure at all. The pressure just vents out of the overflow tube on the reservoir. Not sure what's going on at this point.


***EDIT*** System apparently just had too much fluid in the res. Once I drained some out, I could pressurize the system***

Last edited by Sean K.; 12-10-2017 at 06:24 PM.
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post #59 of 63 (permalink) Old 12-10-2017, 06:23 PM Thread Starter
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So it looks like the air entering my cooling system was doing it through the bleeder valve near the engine (the one with the flattened o-ring that looked like a flat rubber washer).

Everything seems to be fine now.....though this car just seems to run hotter than others.

As for bleeding the system....what worked best was opening the bleeders partially (including the engine breather) and filling the tank without the engine running until the reservoir was full. I pressurized the system with a pressure tester and watched for solid laminar stream from the bleeder screws and tightened them up once I didn't see any bubbles for a while. Turned on the engine with the cap off the reservoir and a small vinyl hose attached to the overflow tube.......let it get hot and puke bubbles and fluid into a catch can under the car until it "burped" a couple of times and dropped the coolant level in the reservoir down to almost the bottom (careful not to actually let it get empty thereby letting air back into the system)....and just kept topping off. Put the cap on once I felt it had burped out most of the trapped air and let it idle for awhile. Got up to 210F before dropping back down to 201 (fans came on half speed at 206-208 and dropped the temp). Left the little white plastic wing nut bleeder on the reservoir alone completely. Pressure tested system and while it doesn't hold 16 psi for long....it drops down to 14 psi or so and stabilizes for hours at a time. No leaks anywhere at this point.
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post #60 of 63 (permalink) Old 12-10-2017, 08:40 PM
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Great to hear you sorted it all out. The temerature on my car behaves similar to yours. I usually, in bumper to bumper traffic the coolant temp goes up to 210F and then it drops to around 205-6. Once the car moves, the temp drops to around 186-192F.
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