Overheating Issue

[Sherlingtonn]

Hi everyone,

I have a 1994 525i thats overheating. After about 10-15 minutes of driving it begins to overheat and also leak coolant (which has always been an issue).

The first thing I did was remove the thermostat but it still overheats. The second thing I did was replace the radiator. This made the car stop leaking coolant but it still overheats. The thermostat is good and so is the water pump.

Now Im not really sure what it can be however, I did notice that the fan right behind the grill (not the radiator fan) is not working so I dont know if that might be the issue.

If anyone has any idea of what may be causing the car to overheat I would appreciate any feedback.

Thanks!

[shogun]

moved to E34 forum

[fo3]

If it's always had an issue leaking coolant than I expect your problem is very bad news - head gasket failure due to not fixing coolant issues sooner.

The fan behind the grill is the auxiliary fan, mainly comes on with the a/c, or if it's really overheating (and would hardly ever come on in a normal working cooling system anyway), it runs off an electrical switch on the radiator on the side near the headlight - did you replace that switch or refit it to your new radiator? Anyway, it shouldn't be needed to run to help cool your car so it's not your main problem. The curse of long engines like an inline 6cyl is greater chance of head gasket failure and a leaking system with a bad radiator like your's apparently had normally means head gasket failure.

Engine compression test, or pressure test your cooling system to verify if you have those tools or access to them. Otherwise let sit for a couple of days, take all sparkplugs out, turn the engine over and look for coolant/water coming out.

[Avec]

Does the 525 have a clutched fan?

Although you say it overheats after 15 minutes of driving, we don't know what type of driving? Highway speeds, or city speeds? If highway, then you have larger issues. If city or traffic, the non-working aux fan coupled with a week main fan will cause issues. I had this very scenario on my E32.

[ross1]

"water pump is good" How do you know this? The factory pumps with plastic impellor are notorious for a loose impellor, sometimes even intermittently.
Are you actually overheating or is it over pressurizing?
Failed HG is a distinct possibility.

[Sherlingtonn]

Update:

So it turns out I had a bad fan clutch. I was able to stop the fan with my hand. The radiator also had about a 3 inch crack. So I went ahead and replaced the radiator, fan clutch and also the water pump.

After replacing the radiator, fan clutch and water pump I left the car on for about 20 minutes and the temp never went passed the half. I then drove it around for another 10-15 minutes and the temp never went passed the half. So I guess the problem is now solved.

However, Im going to replace the valve cover gasket which leaves me with a new question:

Fel-Pro or Mahle?

Thanks for the feedback guys I appreciate it!

[moroza]

IME, Fel-Pro is decent, Mahle a bit better, and Victor Reinz the best (and often OE).

[GreasyE34]

Might seem dumb but did you bleed the system according to Bentley’s?