Overheating Woes

[julielewis]

My 1989 520i Bmw is overheating still. The thermostat, radiator, fans, water pump and fan clutch are all working fine. When I start the car, the temperatuture needle moves past the 12:00 mark and heads for the red.I first noticed the overheating when I was driving in traffic. I stopped the car as soon as I noticed that the guage was close to the red zone. Help!!!!!!!

[Bill R.]

m50 motor available in 89 in the 520, I would venture to guess that you have a plastic impeller water pump on your 89 520 and that the impeller is broken or slipping, it will look fine from the outside and will spin fine from the outside but the pump won't move much water and the car will overheat. Remove your water pump and inspect it.






My 1989 520i Bmw is overheating still. The thermostat, radiator, fans, water pump and fan clutch are all working fine. When I start the car, the temperatuture needle moves past the 12:00 mark and heads for the red.I first noticed the overheating when I was driving in traffic. I stopped the car as soon as I noticed that the guage was close to the red zone. Help!!!!!!!

[julielewis]

m50 motor available in 89 in the 520, I would venture to guess that you have a plastic impeller water pump on your 89 520 and that the impeller is broken or slipping, it will look fine from the outside and will spin fine from the outside but the pump won't move much water and the car will overheat. Remove your water pump and inspect it.


Bill, the water pump has a metal impeller and it seems fine. What do you suggest?

[Bill R.]

cracked head or head gasket seems most likely.







Bill, the water pump has a metal impeller and it seems fine. What do you suggest?

[632 Regal]

Has it been properly bled? Are the hoses rock hard when it's running? (indication of bad head gasket/crackhead)

[Bill R.]

29.4 pound pressure relief on the cap, so if it warms up the hoses are going to be rock hard whether its got a blown head gasket or not at 29 psi, especially when your used to a 13 or 14 pound system on an american or japanese car.











Has it been properly bled? Are the hoses rock hard when it's running? (indication of bad head gasket/crackhead)

[julielewis]

Has it been properly bled? Are the hoses rock hard when it's running? (indication of bad head gasket/crackhead)

It has been bled over and over. The top radiator hose is hot and the bottom radiator hose is cold.

[Dan in NZ]

Sounds like you're having flow problems... When you say the radiator is fine, what do you mean? Have you had it flow tested to make sure it's not blocked?

Is your coolant expansion tank attached to the radiator, or seperate next to the firewall? If it's near the firewall, the line between radiator and tank can clog causing overheating.

[uscharalph]

Sounds like you're having flow problems... When you say the radiator is fine, what do you mean? Have you had it flow tested to make sure it's not blocked?

Is your coolant expansion tank attached to the radiator, or seperate next to the firewall? If it's near the firewall, the line between radiator and tank can clog causing overheating.
If it's the original radiator, it might be time to replace it. I was having cooling problems and decided to overhaul the cooling system. New radiator, water pump, thermostat, hoses and belts. It was under $400 in parts and we did it ourselves. No more cooling problems.

[grave77]

heating up that fast might be a cloged radiator, but this engine cracks the head faster than you would expect, especially if you tried to cool it down by adding water while still hot. check the coolent for any chocolate colore fluid also notice the hoses if they are expanding like a snake then for sure the head is blown or the head gasket.

[julielewis]

Sounds like you're having flow problems... When you say the radiator is fine, what do you mean? Have you had it flow tested to make sure it's not blocked?

Is your coolant expansion tank attached to the radiator, or seperate next to the firewall? If it's near the firewall, the line between radiator and tank can clog causing overheating.

The radiator was tested and it is not blocked. The radiator is about 6 months old. The expansion tank is connected to the radiator.

[Gayle]

In rereading this and your prior thread, I don't see any mention of the aux fan. The purpose of the aux fan is to add extra cooling in more extreme heat situations like in stop and go traffic and when you are running the air conditioning. With an aux fan problem, the car will be fine on the open road and overheat in traffic. I would imagine that Jamica would be hot.

It seems like you have checked everything and probably have checked this too, but it seems worth mentioning.

Also, I have wondered how much experience your mechanic has had with BMWs. We have used the same independent garage for 15 years and have gone through 6 different owners. The first 5 were fine. After reading this board for a mere 3 months, I have realized the current owner is more clueless about BMWs than I am. His ignorance made me think we had big wiring problems on our old 525 when it was just a lamp control module that needed replacing and the locks on the doors were out of sync (both very,very common and minor bmw problems). I've switched to a certified BMW indy. I looked at the website and couldn't find a certified person in Jamica for you. If your mechanic hasn't done a lot of work on BMWs I would try to find someone who has.

[Kalevera]

If the upper radiator hose and that half (or so) of the radiator are hot, yet the lower radiator hose and that half (or so) of the radiator are "cool" (they should be warm): it's a flow problem and there are only three things that can cause it -- inoperative water pump, tstat or radiator. Given that the car has overheated once, the thermostat should be replaced anyway.

best, whit

[Dan in NZ]

And make sure you use the correct thermostat, and that it's the right way around. A few people have had overheating problems when thermostats were put in backwards.

[julielewis]

In rereading this and your prior thread, I don't see any mention of the aux fan. The purpose of the aux fan is to add extra cooling in more extreme heat situations like in stop and go traffic and when you are running the air conditioning. With an aux fan problem, the car will be fine on the open road and overheat in traffic. I would imagine that Jamica would be hot.

It seems like you have checked everything and probably have checked this too, but it seems worth mentioning.

Also, I have wondered how much experience your mechanic has had with BMWs. We have used the same independent garage for 15 years and have gone through 6 different owners. The first 5 were fine. After reading this board for a mere 3 months, I have realized the current owner is more clueless about BMWs than I am. His ignorance made me think we had big wiring problems on our old 525 when it was just a lamp control module that needed replacing and the locks on the doors were out of sync (both very,very common and minor bmw problems). I've switched to a certified BMW indy. I looked at the website and couldn't find a certified person in Jamica for you. If your mechanic hasn't done a lot of work on BMWs I would try to find someone who has.




The aux fans are working. There is a BMW dealership in Jamaica but can I tell I have friends with BMW's who have not had very good experiences with them. They are very expensive as well. I called to see if they had the thermostat for my car and they did not. That was not very encouraging at all. I have found another auto shop that has parts for my car. The mechanic I have is very experienced with BMW's. I am also lucky that my brother is an A/C specialist and he can also assist with fixing my car.

[julielewis]

And make sure you use the correct thermostat, and that it's the right way around. A few people have had overheating problems when thermostats were put in backwards.


I just got a thermostat. The brand is BEHR. I should get it put in by Monday. My car broke down about one and a half hours away from where I live. I have also downloaded a diagram of the thermostat set up to give to the mechanic. The wealth of knowledge that I have gained from this website is amazing. I can actually help my mechanic to solve the problem.

[julielewis]

Finally, the problem is solved. When they took out the radiator it was clogged. Thanks for all your problem-solving tips.

[uscharalph]

Finally, the problem is solved. When they took out the radiator it was clogged. Thanks for all your problem-solving tips.
I'm glad you got it solved Julie.

[Gayle]

How does a six month old radiator get blocked?

[julielewis]

How does a six month old radiator get blocked?


Good question Gayle. The mechanic was actually leaning towards a cracked cylinder head or blown head gasket. My brother decided to check out the radiator himself and the problem was solved. I have been driving around town without any problems. I will take a long drive on Friday and see what happens.

[Gayle]

Good question Gayle. The mechanic was actually leaning towards a cracked cylinder head or blown head gasket. My brother decided to check out the radiator himself and the problem was solved. I have been driving around town without any problems. I will take a long drive on Friday and see what happens.


Sort of makes the point that not all mechanics can work on BMWs. How did your brother figure it out? Did you put in a new radiator? Is there a way to get a blocked radiator unblocked?

[uscharalph]

Sort of makes the point that not all mechanics can work on BMWs. How did your brother figure it out? Did you put in a new radiator? Is there a way to get a blocked radiator unblocked?
I only trust those who know, not only BMWs, but my model / engine BMW.

Probably depends on how blocked and how long it's been blocked. In my case $179.50 for a new radiator was the way to go.

[julielewis]

Sort of makes the point that not all mechanics can work on BMWs. How did your brother figure it out? Did you put in a new radiator? Is there a way to get a blocked radiator unblocked?

After replacing the thermostat he realised that one side of the radiator was cool including the bottom hose. He then thought it through and said that if the head gasket was blown, it should not affect the flow in the radiator. So he took it out and got a radiator specialist to clean it.