weird m20 cooling issues I think its the thermo but not sure

[Brezzi]

Hai Gais,

My newish to me 89 e30 cabrio its having some slight over heating issues and I wanted everyones take on it before I start throwing new parts at it.

Every once in awhile my car temp will go above the middle line not too far though furthest I've seen it go was to the 3/4s line.

-It wont happen when its like 50 to 75 unless its been sitting and idling for awhile.
-over 75 degrees it will happen as soon as I'm stopped and its already at operating temp.
-no matter what as soon as it over heats to the 3/4s line it starts cooling it self off.
-turning on my working AC seems to make it worse
-once on a really hot day it even over heated past the 3/4s line even though I was driving on the highway and had a bunch of air flowing in the engine bay.

I'm guessing its the thermostat? should I buy the 71, 75, or 80 degree one?

thanks:pimp:

[Kozworth]

Hows your fan clutch? Does it have a bunch of coupling fluid slushed all over it, or does it seem clean?

The thing that I dont get is at op temp the tstat should be open flowing coolant to the rad to cool off. If its at op temp, then you idle and there isnt air flowing over the rad, I would lean more towards a clutch because what would cause the tstat to then "close"? If anything, a sticky tstat should take longer to warm up if it was stuck open, or overheat in a linear way.

[Cabriolet]

bleed your system
buy a new fan clutch
replace both temp sensors
= issue will be gone

[Brezzi]

Hows your fan clutch? Does it have a bunch of coupling fluid slushed all over it, or does it seem clean?

The thing that I dont get is at op temp the tstat should be open flowing coolant to the rad to cool off. If its at op temp, then you idle and there isnt air flowing over the rad, I would lean more towards a clutch because what would cause the tstat to then "close"? If anything, a sticky tstat should take longer to warm up if it was stuck open, or overheat in a linear way.

bleed your system
buy a new fan clutch
replace both temp sensors
= issue will be gone

Adam, upon further inspection it does have a bunch of crud on it I'll try what you suggested Cabriolet and hopefully that will fix it.

[TheTacoMan]

Another possibility is a warped head, I had a warped head and it would pressurizer the coolant causing major spikes in and air in the coolant. It could be the issue, mine would not blow heat when it began to spike on the freeway.

Just an idea.

[Brezzi]

Another possibility is a warped head, I had a warped head and it would pressurizer the coolant causing major spikes in and air in the coolant. It could be the issue, mine would not blow heat when it began to spike on the freeway.

Just an idea.

lets hope thats not it.

[Kozworth]

Brent, easiest way to rule out a sensor issue would be to go to harbor freight and by a temp gun. Its like <30 bucks.. you shoot it pre and post the tstat. When warmed up, it should be op temp both pre and post (about 180 degrees is what cars run at). If you are reading 180 both sides at op temp yet the gauge is creeping, the sender thermister is probably bad.

[Brezzi]

Brent, easiest way to rule out a sensor issue would be to go to harbor freight and by a temp gun. Its like <30 bucks.. you shoot it pre and post the tstat. When warmed up, it should be op temp both pre and post (about 180 degrees is what cars run at). If you are reading 180 both sides at op temp yet the gauge is creeping, the sender thermister is probably bad.

good idea! I needed an excuse to buy a temp gun so I'll prob do this too. Might just start out replacing the fan clutch because that seems to be a common thing. Then checking the sensors with the gun to figure out if they're bad.

[Brezzi]

took a video because I was bored:


Also I poked some folded up paper at the fan while it was at operating temp to see if had a weak spin, it didnt stop or slow down so now I'm second guessing the fan clutch?

[Cabriolet]

Still 100% set on my first analysis

[Quinthirty]

Thanks for posting this. I was just experiencing the same thing. My gauge is exactly where yours is going, and tonight it just went to almost 3/4. While idling w/o the A/C the aux was off, same temp. With A/C on, no change. Mine is intermittent though, sometimes it would go to 1/2, and just below 1/2. Mind boggling. I checked fuse #3, it was ok. I had the thermo-switches checked two weeks ago and it looked good. It seems that I'm down to the following:

1. fan clutch
2. thermo sensors

I definitely have a leak though. I'm just waiting for my pressure tester and leak tester to arrive to confirm whether its coming from the head gasket. I hear the fluid "boiling" in the reservoir after I switch off the engine so it sounds like there's air. I top up the fluid every 3 days.

[The Bimm]

I had the same problem its your fan clutch its not swithing over to the high speed the fans spinning but only at one speed just chang the clutch but order the fan clutch tool to take it off other wise its usually a struggle to break it loose and its reverse threaded then juack the front end up a little to bleed the coolant if you do bleed it so is theres any trapped air bubbles jacking up the front should pop them out

[E30Gus]

I had the same problem its your fan clutch its not swithing over to the high speed the fans spinning but only at one speed just chang the clutch but order the fan clutch tool to take it off other wise its usually a struggle to break it loose and its reverse threaded then juack the front end up a little to bleed the coolant if you do bleed it so is theres any trapped air bubbles jacking up the front should pop them out

What?