Overheating issues with S50

[jink0619]

Use BMW coolant for the S50.. I've owned so many e36 m3s and have seen the waterpump fail like this randomly? When was the last time it was replaced? If u don't know order the oem replacement but with the metal impaled.. Try that

You are right, ive done 3 swaps so far and with the m52 and s50 i used prestone and both kept over heating, but my lastest swap i used bmw coolant and its been running nice and cool. Also when u go to pour the coolant in forget all the bleeding n doing it on the hill or in the bushes..watever, just pour it in slowly...nice n slow :D

[edsel1134]

Impeller •

[edsel1134]

Use BMW coolant for the S50.. I've owned so many e36 m3s and have seen the waterpump fail like this randomly? When was the last time it was replaced? If u don't know order the oem replacement but with the metal impaled.. Try that

[jink0619]

What coolant are you using?

[TheRealE30kidd]

had the same problem when I was using the M42 radiator

[Wh33lhop]

Ugh. I fucking hate cooling system issues.

Sorry, nothing else to add to this thread. I just fucking hate cooling system issues.

[e30austin]

It was replaced with an S52 metal impeller water pump at some point. I took it out and inspected it before installing the engine in the car.

[butters]

That is a bummer, I'll say a prayer for your cylinder head. You replaced the water pump, correct?

[e30austin]

Bump. New thermostat installed, still doing the same thing. Even drilled a hole in the thermostat to ensure it was bleeding out all the way.

Not sure what I'm doing wrong. Still no oil in the coolant, or coolant in the oil, so I think head/HG are ok.

[e30austin]

'89 325i with S50. Using late model M20 radiator/expansion tank and 80 deg thermostat.

Yesterday, I pulled the radiator to put wire up my SPAL fan (sick of using the stock AC fan.) I realized the radiator looked kinda clogged, so I attempted to flush it with a hose. Thought it worked, but clearly not. Started car up, turned thermostat to hot, turned blower on and left cap off. Appeared to bleed out fine, so at the end of the day, I went home.

Made it on the freeway about 3 miles away and saw the temps creeping up, so I clicked the fan on and kept going. Got another mile down the road when I saw steam coming from under the hood. Pulled over and popped the hood to find the cap had been blown off the expansion tank. Let it cool down a bit, started it up, added the necessary amount of coolant, saw it appeared to be acting normally and got back on the road, and then it started to overheat again. Repeated this about 3 times over the course of an hour until I finally got it back to the shop.

I thought maybe I didn't bleed it well enough, so I parked it on a hill at the shop and tried to bleed it to no avail. Felt the radiator and found a cold spot, so I ordered a new Nissens unit. Installed that this afternoon, parked it on the hill and attempted to bleed it again with cap off, heater set to hot and on full speed. Still doing the same damn thing, only now, it's staying right above the half mark and the temp comes down slightly when I rev it up to 3k. Then, after a while, it starts to overheat again.

I've never had this much of an issue bleeding coolant, particularly on 24v cars with M20 radiators. Normally they just bleed themselves. I never let it get into the red, but I know M/S5X are prone to having HG issues. Hoping this is not the case. It was fine before, would have to kick the fan on if idling for a while (probably because of the old shitty radiator) but never had any issues like this.

Any help is appreciated at this point. Thanks.