Overheating 525i 96

[fenhow]

Hi all. The message borad has been great. I am wondering if someone out there can help me.

Problem - 1996 BMW 525i Overheating

Already Done - Thermostat, Waterpump - metal impeller, Radiator Test and Flush.

Compression Check - OK

I am still overheating. It is driving me crazy.

Getting a lot of steam and boiling in the overflow tank. Can anyone give me some insight?

Thanks alot.

[RobPatt '93 525ia @123K]

No leaks, no blockage; perhaps no circulation? 1. Fan bad? 2. T-stat installed backwards? 3. System not bled of air?

-Rob


Hi all. The message borad has been great. I am wondering if someone out there can help me.

Problem - 1996 BMW 525i Overheating

Already Done - Thermostat, Waterpump - metal impeller, Radiator Test and Flush.

Compression Check - OK

I am still overheating. It is driving me crazy.

Getting a lot of steam and boiling in the overflow tank. Can anyone give me some insight?

Thanks alot.

[632 Regal]

air pocket?

[632 Regal]

hmm... steam, if it is bled correctly I would have to guess that your headgasket might be the unfortunate culprit.

[Anton CH.]

M50 is very tolerant to air pockets. I believe the coolant system in our cars is meant to be pressurized. With the expansion cap closed, are the coolant hoses rock hard? This would be a good indictication of air seeping into your coolant system from the combustion chamber.

[fenhow]

hmm... steam, if it is bled correctly I would have to guess that your headgasket might be the unfortunate culprit.

Not sure if the system is properly bled. I would be a very happy camper if that was the problem. How do I accomplish this?

Thanks..

[fenhow]

I was thinking the fan. How can I check that as well? How do I know if it is working. I am just replacing parts one at a time here...

Thanks

[fenhow]

Hi, expansion cap? Is that also known as the radiator cap? If so, the hoses do become hard when the system starts heating up but not at first. I can still squeeze them but it does take some force?

Where would the air be coming in from?

[fenhow]

Man, I dont want to hear that. The head gasket is the last place I want to go for this one. I say bleed..... bleed is the problem :-)

[fenhow]

One more thing, I get no heat when turn on my heater.

[Scott C]

One more thing, I get no heat when turn on my heater.
There is an adjustment on the radiator to allow air to be bled out (screwdriver flat blade)... And it is a pain in the arse to get the air out! Just don't drive it till you do or you may NEED to get a head gasket. I also ended up taking very hard corners to get all the air out - left and right to allow the heat to work again.

Good luck,
Scott

[fenhow]

Great, do i loosen it all the way, take it out or what? How will i know all of the air is out? Right now it is only hot air coming out of that thing.. Will fluid eventually come out?

Thanks

[Scott C]

Great, do i loosen it all the way, take it out or what? How will i know all of the air is out? Right now it is only hot air coming out of that thing.. Will fluid eventually come out?

Thanks
Yes loosen it, you will hear the suction, but don't let the engine overheat and keep putting coolant in - it will continue until most of the air is out - I still had to drive mine to get it out (fairly sharp turns)

Scott

[632 Regal]

Optimisticly speaking, with no heater you have an air pocket in there. The air thats comming out could be boiling water from the air pocket?

Lets see if I have info on properly bleeding handy...nope. Do a search here on bleeding, there are more than a few detailed posts on the subject.

[632 Regal]

heres some:

http://www.bimmer.info/forum/showthread.php?p=26154&highlight=bleeding

http://www.bimmer.info/forum/showthread.php?p=21241&highlight=bleeding

http://www.bimmer.info/forum/showthread.php?p=19190&highlight=bleeding

[Anton CH.]

So you replaced a thermostat, waterpump, flushed the radiator and perfromed a compression check but never bothered to bleed the system? Something just does not add up. But the fact that heater is not working does suggest that there is an air pocket in the system. Try rocking the car up and down then drive it around the block (without the temp going into red), let it cool down. Repeat this step over and over. The car will continue to suck water on each cycle and buble air into the expansion tank. That was the only way I could flush the coolant in a stubborn Dodge Caravan. Never had problems with the 525 however.