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 Posted: 04-26-2014 05:21 pm
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Barthol
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It seems that my JH ( bought last summer ) gives me more and more issues to solve.

Today We had a hot day ( At least for Denmark:-)
it was 21 deg C app 68 deg F.
i was running the car for a longer time at 80 MPH and noticed that it seemed to get to hot.

hanging the temp gauge to one with numbers on indicated that my cooling water temp would be between 92 and 98 deg C app 197-208 deg F.

I checked my radiator and noticed that it did not get equally hot all over .
The lower left corner ( close to the return Hose) was much colder than the rest of the cooler.
I took of the cooler and tried to soak it in a mild citrus acid solution , but the problem did not disappear.
Then I opened the thermostat housing to check the thermostat , and guess what! No thermostat was mounted.

Reading the different threads tells me that I definitely have to mount a new thermostat with a lower "Splash disc" .

I guess that the thermostat will not solve the problem either, just making the engine warm up faster.

Any Ideas on how to proceed ?

BR
kim

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 Posted: 04-26-2014 10:34 pm
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Art DeKneef
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It sounds like the radiator might be partially blocked. If it is the original it might be time to have it looked at.

Other things I can think of that could cause it to run hot:
How fresh is the fluid and what is the ratio of water to antifreeze?
The gauge could be going bad.
Engine timing is off causing the engine to run hot.
Is there a fan shroud?
Add a spoiler to force more air to the radiator.
Engine cooling tubes blocked.

First thing I would do is get a thermostat, then flush the system if you do not know the condition of the fluid and put in new. Verify the gauge is working properly.

Art

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 Posted: 04-27-2014 01:38 am
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Jim Ketcham
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Please read the posts below on thermostats for the lotus engine which requires a dual stage thermostat. A single stage or no thermostat will result in overheating. This link explains the Lotus cooling system.
http://www.gglotus.org/ggtech/907overheat/907overheating.htm

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 Posted: 04-27-2014 02:06 am
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Jim Ketcham
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Please read the posts below on thermostats for the lotus engine which requires a dual stage thermostat. A single stage or no thermostat will result in overheating. This link explains the Lotus cooling system.
http://www.gglotus.org/ggtech/907overheat/907overheating.htm

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 Posted: 05-17-2014 09:43 am
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Barthol
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Hi Guys,

Thanks a lot for the input.

I did put a thermostat in the car today and a test-drive immidetely showed that the temperature had dropped .

It now stayed between 86 and 90 deg C ( 187-194 deg F).

So even though my radiator might not be working 100% the mounting of the thermostat seemed to solve the problem ?

Br
Kim

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 Posted: 05-18-2014 03:17 am
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Tom Bradley
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My understanding is that engine coolant temperatures usually run right around the boiling point of water (100C). I think the lack of a thermostat was probably keeping your engine temperature too low most of the time. Does your gas gauge also read high? A common problem is that the voltage stabilizer feeding the gas gauge and engine temperature gauge can stop regulating so the full system voltage goes to the gauges making them read high. Not a serious problem as long as you are aware that the readings are somewhat high.

My guess is that the new reading you got is from somewhat different conditions, like a cooler day, shorter time running at full speed, etc.

Do you have a copper radiator? I notice that some people have been trying to sell aluminum ones claiming that they are better. To put it simply, they are not. But as long as it is in good shape, either one should be adequate. Temperature differences across a radiator are normal. No material has perfect heat conduction.

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 Posted: 05-18-2014 04:44 am
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Jensen Healey
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Hi Tom,

The Lotus 907 doesn't flow water correctly if the thermostat isn't installed. This is not a small block Chevy!
You MUST have the CORRECT duel stage thermostat installed or the engine will overheat.

Cheers, Kurt

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 Posted: 05-18-2014 08:04 am
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Barthol
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Hi Tom,

I really ran it hard and for at least 1 and a half hour, and it definitely ran colder.

For the temp measurement i mounted a modern pt100 element with its own gauge , so I am pretty sure that the temp measurement is correct.

I have the old copper radiator ( two rows) and it is definitely not 100% ok as the lower left corner do not get warm. ( close to the return to the engine)

I guess they the problem of running without the thermostat is they the majority of the water will circulate in the pump / radiator without entering the engine?

Anyway I will leave the thermostat in and watch my temperature.

With regarding to the reading of the fuel gauge it it almost the opposite, even If I fill the tank it only shows 3/4 full, and empty seems to be around 1 /8 ?

Br
Kim

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 Posted: 05-20-2014 12:57 am
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Tom Bradley
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I went out and looked at the spare water pump core and thermostat I had sitting around. I stand corrected. The water flow will definitely not be correct without that thermostat. This is a weird design.

When I had trouble keeping my engine temperature down it mostly happened when the car was not moving. So I guessed that the problem was not enough air flow through the radiator by the plastic fan. Putting a shroud around the fan did not have much effect. Re-coring the radiator, first to the standard two rows, then to a three-row also did not help much (I did not do a thorough check with a temperature probe as you did). I got an electric pusher fan from Delta and that fixed it well enough so I did not have to worry. For a while I also had on a front spoiler, but that did not seem to make any difference at any speed and made it more difficult to get over speed bumps, so I eventually took it off. Turning on the water flow to the cabin heater also reduced the engine temperature somewhat, though this is not a very comfortable method on a hot day.


My oil pressure when idling was also getting scary low, so some time later I also replaced the oil cooler hoses and the oil pump gears. That was the change that made the most difference in temperature overall. But as I recall, replacing the gears was a fairly difficult task.

I am not sure why your gas gauge never gets to either full or empty. Perhaps someone replaced it with something from a different car? As long as it is working I would not mess with it.

Hope this is of some help.

Tom

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 Posted: 11-28-2015 07:43 am
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jerro27
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pls jensen overheatng new 3 core allumium rad new thermostat top tank hot bottom cold and hose cold heater system bypassed

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 Posted: 11-28-2015 02:09 pm
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Brett Gibson JH5 20497
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Flush the block.

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