Cooling Problem

[525im20]

Hi folks, just hoped someone might be able to help.

My friend and I are trying to get the cooling working right on a 1989 e34 525i with an m20 engine in the uk. The car blew its rad and cooling after cracking its cylinder head, we have replaced the head gasket and radiator and flushed the oil out of the cooling system, replaced the engine oil and verified we are not getting water in the oil and vice versa. We have drained and refilled the cooling system (several times) and so far have ended up replacing the thermostat and the temprature sensor.

We have followed the correct procedures and even tried the methods suggested on bmwe34.net but so far were still getting overheating with no perceptible flow to the radiator, all that happens is the engine runs until the guage shows its starting to overheat and the radiator part of the circuit stays cold.

We have yet to verify that the new thermostat isnt a dud but in the absence of that can anyone help with some advice?

Thanks.

[uscharalph]

So the cooling system has been bled? That little trick with drilling the hole in the thermostat really helped me with the refill and bleed, although we had to go through 5 or 6 bleeds that night and I bled it one more time the next morning. All's great now.

[632 Regal]

persistance is the key, ralph is dead on.

[DanDombrowski]

When I did a coolant flush on my girlfriend's Camry, there was no drain plug in the entire system, so I just had to undo the bottom hose and then flush the block with water by filling the radiator with water and having it drain out through the top radiator hose. You might try disconnecting the upper radiator hose to see if any amount of coolant is flowing through, then again hers is a completely open system, so its ok if the rad isnt sealed. That might not be the case on our cars. Worth a try.

[525im20]

So the cooling system has been bled? That little trick with drilling the hole in the thermostat really helped me with the refill and bleed, although we had to go through 5 or 6 bleeds that night and I bled it one more time the next morning. All's great now.

Bled many times unfortunately, nothings working, today we had the stat out again and checked it works ok, it also has the hole drilled.

[uscharalph]

Here's some bleeding pointers:

1. Put the front of the car on ramps.
2. Turn the heater on (You need to get coolant in the heater also) (Mine had a leak & I had to bypass)
3. Open the radiator cap and bleeder screw on top of the radiator.
4. Slowly keep pouring coolant into the overflow, stopping when it gets to the top, when it goes down repeat.
5. Keep your eye on the needle, don't let it get past 3/4.
6. When almost no bubbles are coming out the bleeder, put the bleeder screw back in and close the radiator cap.
7. Shut down the engine.

Mine was still overheating some (Standing Still) when I drove it home. It didn't overheat on that drive. I bled it again in the morning and it's been OK since. Did you say you got a new radiator?

[525im20]

Here's some bleeding pointers:

1. Put the front of the car on ramps.
2. Turn the heater on (You need to get coolant in the heater also) (Mine had a leak & I had to bypass)
3. Open the radiator cap and bleeder screw on top of the radiator.
4. Slowly keep pouring coolant into the overflow, stopping when it gets to the top, when it goes down repeat.
5. Keep your eye on the needle, don't let it get past 3/4.
6. When almost no bubbles are coming out the bleeder, put the bleeder screw back in and close the radiator cap.
7. Shut down the engine.

Mine was still overheating some (Standing Still) when I drove it home. It didn't overheat on that drive. I bled it again in the morning and it's been OK since. Did you say you got a new radiator?

Rad came from a low mileage scrapper but we were told it was a runner, we have checked it flows ok.

Today we had the new thermostat out and verified its working, we re-bled the system several times, even had the car jacked nose up to max height on axle stands and did much like you suggest, same thing - cold rad, we are also apparently not getting any heat from the heater matrix (solenoids tested working).

We are almost certain its not airlocking, we flow tested all the hoses and the block but starting to think theres a blockage in the return circuit. There is a little residual oil in the water but we had planned to flush it finally with heavy duty flushing agent once car was running ok, it needs to be moved asap.

Any ideas folks, we are going

[uscharalph]

Hopefully the radiator is OK. I got a brand new Nissens off eBay for $175.50. I'm glad I got a new one. I plan on keeping this car a while.

When the radiator is off the expansion tank, there's a small hole towards the top. Coolant should be weeping back into the radaitor through this hole. My old radiator was clogged there. I think you can just replace the expansion tank.

If you haven't done this already, I would start from cold, fill the expansion tank and take the car for a little ride. This seemed to help my car fill the entire system. Just keep an eye on the needle and see what it does.

[525im20]

Hopefully the radiator is OK. I got a brand new Nissens off eBay for $175.50. I'm glad I got a new one. I plan on keeping this car a while.

When the radiator is off the expansion tank, there's a small hole towards the top. Coolant should be weeping back into the radaitor through this hole. My old radiator was clogged there. I think you can just replace the expansion tank.

If you haven't done this already, I would start from cold, fill the expansion tank and take the car for a little ride. This seemed to help my car fill the entire system. Just keep an eye on the needle and see what it does.

The rad does seem to be ok, there is flow through it and the hole isnt blocked, we checked.

I do plan to flush it once its running safe but until we get circulation dont see the point of dumping in a load of expensive flushing.

Suspicion is currently blockage on the return system, might check that today if it stops raining heavy

[525im20]

The rad does seem to be ok, there is flow through it and the hole isnt blocked, we checked.

I do plan to flush it once its running safe but until we get circulation dont see the point of dumping in a load of expensive flushing.

Suspicion is currently blockage on the return system, might check that today if it stops raining heavy

Return system an all pipes ok, flow going thru matrix and block ok, seems like no pressure from water pump but found out its only a year old, have to check for clogged pump before go any further.