Author Topic: Overheating MYSTERY! HELP HELP (Read 4153 times)

AlpineRob · « **on:** May 17, 2010, 11:06:49 AM »

Okay...1991 318is coupe..m42..of course.

Just replaced the water pump AND thermostat. I wish i knew before hand that i put in a 92c thermostat, because i never would have done that. I wanted a much cooler one. So maybe someone can say this is my problem but heres my issue(s):

I cannot seem to get all the air out of the system. I have tried both methods (bleeding with the radiator cap off only, as well as just bleeder screw off only.) Nothing.. My temp gauge settles between center line and 3/4. after a few minutes it will reach 3/4..not good.

I have no heat. which means i have air in the system.

My fan clutch has only locked a couple times, but not enough. = air.

Could this all be caused by the thermostat being the wrong kind? what if it wasnt put in to the exact orientation as the previous one?

Before these repairs, the temp was perfect in the car..just below center. I made the repairs as a precautionary step. HELP?? I am out of ideas. Thank you

Jorgeconrico · « **Reply #1 on:** May 17, 2010, 11:30:13 AM »

Did you try bleeding it on a hill? That worked for me.

Cre8toR · « **Reply #2 on:** May 17, 2010, 11:13:39 PM »

Yeh they are a pain to bleed, a hill can help but with mine i had to bleed it then let it cool bleed it again

DesktopDave · « **Reply #3 on:** May 18, 2010, 06:36:02 AM »

I pulled both main coolant hoses, filled them both one at a time, then bled it facing uphill.

Does your electric aux cooling fan come on at all? The fanstat on the radiator or fan resistor can fail & cause trouble too.

flyinglizard · « **Reply #4 on:** May 18, 2010, 08:41:05 AM »

If the stat is not opening, or the air bubble restricts the flow. None of the fans will come on, due to no hot water getting to the switch and the clutch fan will not get enough hot air to engage. The rad must get warm to both hoses...
That is why these cars ruin heads so often. No coolant flow. The 92 * stats is a little high. I use the 80*.. HTH. MM

RED IS 91 · « **Reply #5 on:** May 18, 2010, 11:37:51 AM »

This is my routine which I've used numerous times.........

1)Fill system to the top.
2) Start car ,turn heat on high with fan on.
3)Once cars temp starts to rise
4)I grab the throttle cable and rev the engine to 1500-2000 rpms and then open the bleed screw to burp the system.

5)Once I see no more bubbles coming out and the car is at operating temp with heat coming out of the vents I close it up top off the fluid and take it for a ride and watch the gauge.

6)Come back from ride ,check fluid level ,top off if necessary and repeat the procedure one more time for good measure.
This has always worked for me.
I'm not saying it's the only way or best way but it works for me.

good luck
If your thermostat is not opening then you have other issues.I have a 88* wahler in my car and the needle is in the middle most of the time.

cristimm · « **Reply #6 on:** May 18, 2010, 12:27:17 PM »

Quote from: RED IS 91;92595

If your thermostat is not opening then you have other issues.I have a 88* wahler in my car and the needle is in the middle most of the time.

Mee too 88C Wahler. BEHR is good as well, I wouldn't buy anything else.

mtle30 · « **Reply #7 on:** May 18, 2010, 02:50:02 PM »

Im having the identical problem as AlpineRob, however so far I've only changed the thermostat and I think the mechanic put a 92*. Under normal highway driving the needle sits just above half, but if traffic slows down (as it always does) it takes about 5 minutes until it makes its way to just under 3/4's.

I've purchased the 88* Behr thermostat and decided to get a water pump at the same time, one with a metal impeller. I know that my aux fan works because when i turn on the AC, it turns however I may have a problem with the resistor. I will try and bleed the system as RED IS 91 said and ill post back if everything comes to normal.

PumpItUp · « **Reply #8 on:** May 18, 2010, 04:40:37 PM »

did your replacement have a bleeder hole?
http://m42club.com/forums/showthread.php?t=11607

92 degree thermostat is meant for the clutch fan
if you delete the clutch fan you should get 88 degree, so your electric fan isn't always coming on unnecessarily and bogging down the car. not sure about the 80* that flying lizard mentioned from the e36 m42s.

i deleted the clutch fan but didn't install any replacement yet. so i have to avoid traffic jams on hot days. but with the 88* even after 5 minutes of idle it only gets about 2mm right of the center line on the temperature gauge. although i just added redline water wetter. i think it actually works because before the temp would climb faster when the car was not moving, even on a cool night.

mtle30 · « **Reply #9 on:** May 19, 2010, 03:36:43 PM »

Quote from: PumpItUp;92606

did your replacement have a bleeder hole?
http://m42club.com/forums/showthread.php?t=11607

I havent received it yet, i'll post once I get it. Did the hole make a difference in the end? What exactly was the RTV for?

PumpItUp · « **Reply #10 on:** May 19, 2010, 05:28:38 PM »

a lot of owners are frustrated with bleeding this system, while it was straight forward for me, so i guess it did make a big difference even though i drilled a smaller hole than the oem wahler. as for rtv, its good to use to avoid coolant leaks, since its a high pressure area. for this application rtv blue is recommend. theres a bunch of sealing/silicone products out there, its your choice if you want to bother with them. for my oil pan i just used the gasket.