M20 Running hot Version 12342142.0

[coldweatherblue]

know this has been asked to infinity but just looking for some ideas on why my m20 runs hot.

starting about 2 weeks ago it creeps up to the 3/4 while idling. I used to have to jumper the aux fan to "low" setting and that kept it below the 1/2 way mark but recently it's gotten worse, even with the aux fan jumpered to "high" all the time it creeps up when the car is stationary.

also when I turn it off, then let it sit for ~3 minutes when I get back in the car the temp guage is past 3/4, then when I turn it on the temp goes back down.

so I've read about this and have done the following:

have flushed coolant 5x in past year.
have bled multiple times using jlevie's method.

the thermostat (factory temp), radiator, coolant temp sensors, water pump, hoses, fan clutch have all been replaced less than 5k miles ago.

I also replaced C191.

so in short, I've fixed everything I can think of but the car still runs hot at idle then comes back down with running. it's running hot based on infrared thermometer as well so not just the guage.

ideas? thanks

[jlevie]

Were the replacement parts new, OE, parts? Aftermarket Pacific rim or used parts could be an explanation. Assuming that a bleed doesn't release a significant amount of air and that the engine temperature is normal when the car is moving at 35mph or above, a clogged cooling system, bad fan clutch, bad thermostat, or bad pump would be the logical suspects.

If a bleed results in the release of a significant amount of air, a head gasket leak is the logical suspect.

[coldweatherblue]

could be clogged in the engine block, like I said I've tried flushing it at home but doesn't help much. All parts were from pelican parts and are OE german made.

no air comes out when I bleed it.

[4evere30]

im interested to see were this goes , i had this same thing happening last summer ; never did figure out exactly what it was , and a month or two later i blew my head gasket .....maybe that had something to do with it? hopefully not for your sake though... are you running boost or just stock?

[coldweatherblue]

stock m20b25

[coldweatherblue]

flushed and bled the system again today. no change. guage still climbs past 1/2 when idling.

My tach just started jumping around occasionally so could be the guage also but usually the guage is consistent.

although I measured the temp on the thermostat while the car was at 3/4 per the guage and it was 172 farenheit, valve cover was 165. not sure exactly how to interpret this but just fyi.

[Quinthirty]

Have you checked the following?

1. Fuse 3, 17
2. Thermo-switch
3. Coolant Temp sensors
4. All relays that trigger the auto fan, low and high temp i.e. K7 (don't remember the other one).

Hope this helps.

[coldweatherblue]

Fuses are good. Thermo switch is new. Coolant temp sensors are bosch and are new.

Haven't checked the relays but the aux fans work when jumpered. I currently have the fan on "low" all the time. Strangely the fans don't automatically turn on (even with a new switch and new radiator) but work when jumpered, which doesn't make sense to me. They obviously work and I'd assume since the fans work the relay is working, they just don't turn on when they should, even though the thermo switch is new.

Drove to work today, 50 degrees ambient temp, guage was almost 3/4 the whole way there.. pissing me off. Like I said I've /flushed/replaced almost everything I can think of..

Could be a massive clog in the block or I guess the HG but the car doesn't use coolant, doesn't mix coolant w/ oil, has good compression (170 +/- 10psi across) and doesn't build up air..

[3vilE30]

What weight/brand oil do you have in right now? Thinner oils tend to make m20's run hotter then normal.

[E30Gus]

Is the system building up pressure when hot? Possible coolant res. cap leak?

[E30_fiend]

Dude, change your fan clutch...

[coldweatherblue]

castrol gtx 20w50

yes, system has pressure when hot. however the res cap is one thing I haven't replaced.

fan clutch is behr and brand new.

[E30Gus]

I had two brand new fan clutches delivered to me that were bad out of the box. I would double check it.