Overheating, symptoms inside

[Garlic Breath]

Car: 1995 525iA

I noticed a week or so ago the temp needle was hovering a tick mark above the 12:00 position, it's usually nuts on. I didn't get to drive it though because the damn drive shaft was rubbing against the heat shield due to the tranny mounts were blown out. That’s fixed now and I was driving on the expressway home from the indy going about 70 MPH the coolant temp chimed and I immediately pulled over. I checked the coolant level and it was full and I also cracked the bleed screw and no air came out, just coolant. I was able to cool it down within seconds by turning on the heater. The radiator was hot on the expansion tank side but the other side of the radiator was not very hot.

The radiator is 6 months old along with the thermostat. I swapped out the clutch fan yesterday because it was easy and I had one. The aux fan is operating properly. The water pump, as far as I know, is the original with 71K on the clock.

Diagnosis bad water pump or air still trapped?

Thank you for your consideration.
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Low a behold it is the water pump. I had to get it towed home while my wife went to the dealer to pick up the part. The plastic was complete except that it spun freely on the shaft. Everyone is happy now and I learned a lesson. When you change your radiator and thermostat you may as well change the water pump too!

:)

[rickm]

I had a similiar problem...then one day it went into the red on a mountain road, I coasted to a halt when I could and the upper radiator connection to the radiator cracked. Replaced it, didn't help....so I replaced the water pump, it's all good. I believe that the original water pumps had plastic impellers, which have a limited life. You can purchase replacements that have metal impellers for around the same price. (Someone correct me if I'm wrong here)

[dacoyote]

Sounds like the water pump.

If it's the plastic one you should replace it anyway.

-Charles

[632 Regal]

agreed as mentioned, it also could be the thermostat malfunctioning. I would personally replace both and see how things go.

[dacoyote]

I agree, its right there when you change the water pump.

(I cannot remembier.. but for some reason I think you have to take it out to get the pump out... or it's right behind it)

-Charles

[Garlic Breath]

I should have changed the water pump when I did the rad and t stat but I didn't.

Would the heater at 100% on have that much of an effect on the cooling?

[dacoyote]

Yes, as long as some coolant is moving the heater running full blast will pull the temp down..

For example... my beater minivan didn't have a fan in the front for a long time... right up till I got tired of the 90 degree weather and running the heater full blast at the same time.

-Charles

[dacoyote]

Just as a comment, you should prop replace the tstat when you have it apart, over heating is hard on it... and the engine only handles so many over heats before it breaks...

-Charles

[uscharalph]

I should have changed the water pump when I did the rad and t stat but I didn't.

Would the heater at 100% on have that much of an effect on the cooling?
That's amazing. I just changed out my radiator, thermostat and hoses & belts and wasn't going to do the water pump. A couple guys around here along with my brother talked me into it. I can't believe I listened (I'm a little hard headed as well as cheap). Thanks Guys!

[uscharalph]

On the heater question: I believe you initially get the benefit of cooling down the system, but once everythings hot the benefit is minimal. IMHO

[dacoyote]

Yeah.. thats the "hard" thing on the bmw's... save a dollar now... spend ten fixing it when it breaks....

I will be really glad this winter when I got months to work on it as I drive beater van one.

It has come back to bit me a couple times already.

-Charles

[Garlic Breath]

Car: 1995 525iA

I noticed a week or so ago the temp needle was hovering a tick mark above the 12:00 position, it's usually nuts on. I didn't get to drive it though because the damn drive shaft was rubbing against the heat shield due to the tranny mounts were blown out. That’s fixed now and I was driving on the expressway home from the indy going about 70 MPH the coolant temp chimed and I immediately pulled over. I checked the coolant level and it was full and I also cracked the bleed screw and no air came out, just coolant. I was able to cool it down within seconds by turning on the heater. The radiator was hot on the expansion tank side but the other side of the radiator was not very hot.

The radiator is 6 months old along with the thermostat. I swapped out the clutch fan yesterday because it was easy and I had one. The aux fan is operating properly. The water pump, as far as I know, is the original with 71K on the clock.

Diagnosis bad water pump or air still trapped?

Thank you for your consideration.
-----------------------------------------------------------

Low a behold it is the water pump. I had to get it towed home while my wife went to the dealer to pick up the part. The plastic was complete except that it spun freely on the shaft. Everyone is happy now and I learned a lesson. When you change your radiator and thermostat you may as well change the water pump too!

:)
I forgot to mention that the pump the dealer supplied had a metal impellor

[dacoyote]

I forgot to mention that the pump the dealer supplied had a metal impellor

Yes sir... the plastic ones didn't last....

I have heard rumors of some new plastic ones however???

-Charles

[rickm]

I heard the plastics last anywhere between 50 and 75k. This one I just replaced made it 71k. :P