overheating engine

[paul crowhurst]

can any one help me.I changed the rad and fan clutch on my 91 525i se auto just over a week ago as the rad had a leak and i was getting overheating in traffic but not when i was running at speed.It seemed to do the trick,i had put in new coolant and bled the system.I drove the car over 200 miles during the week checking the fluid level daily and kept an eye on the temp guage and it did not go over half way and then while driving at speed on the way home i got an overheating warning .I pulled over and checked the fluid level but it was ok but the car had to be towed back as it would keep overheating.It is up on ramps now and i have been trying to re bleed but it doesnt seem to want to release any air and is still overheating.I have noticed that hot air does not come out of the heater blower in the car though.It did before i changed the rad though and started messing around with it!It is an m50 engine.any advice will be gratefully recieved.
thanks
paul

[dacoyote]

Still got the plastic water pump in it?

Charles

[paul crowhurst]

hi charles, i dont know if it is a plastic water pump as i have not had a look....yet.The car has done about 120k though

[dacoyote]

hi charles, i dont know if it is a plastic water pump as i have not had a look....yet.The car has done about 120k though

That would be one of the first things I would suggest checking. The plastic pumps break enough that bmw made new metal ones. While you have it pulled apart I would also change the stat.

-Charles

[632 Regal]

If you dont know when the waterpump or thermostat was replaced then it's time to replace them...its part of normal maintenance anyways. If you get an authentic BMW stat it will have a check valve in it if not then you should drill a small (1/8) hole in it and point that UP to help bleed the system. When you bleed it you do leave the heater on hot and blowing dont you?

[uscharalph]

hi charles, i dont know if it is a plastic water pump as i have not had a look....yet.The car has done about 120k though
Also, when you changed the radiator, did you change out the radiator cap?

[paul crowhurst]

no i did not change it.Is there a reason why you should?

[paul crowhurst]

yes i had the heater on and blowing although no hot air has come through into the car!There is some play in the water pump shaft so a change would probably be a good thing.

[uscharalph]

can any one help me.I changed the rad and fan clutch on my 91 525i se auto just over a week ago as the rad had a leak and i was getting overheating in traffic but not when i was running at speed.It seemed to do the trick,i had put in new coolant and bled the system.I drove the car over 200 miles during the week checking the fluid level daily and kept an eye on the temp guage and it did not go over half way and then while driving at speed on the way home i got an overheating warning .I pulled over and checked the fluid level but it was ok but the car had to be towed back as it would keep overheating.It is up on ramps now and i have been trying to re bleed but it doesnt seem to want to release any air and is still overheating.I have noticed that hot air does not come out of the heater blower in the car though.It did before i changed the rad though and started messing around with it!It is an m50 engine.any advice will be gratefully recieved.
thanks
paul
What kind of radiator did you install? It was a new one right?

[uscharalph]

no i did not change it.Is there a reason why you should?
I don't know how many overheats these caps have in them, but I replaced mine when I overhauled the cooling system (New radiator, water pump, thermostat, hoses and radiator cap. I had previously changed the fan clutch). For $5-6 it couldn't hurt.

Also, is your radiator cap the new type or is it the original?

[dacoyote]

yes i had the heater on and blowing although no hot air has come through into the car!There is some play in the water pump shaft so a change would probably be a good thing.

In a word... yeah

Change the stat while you have it apart, also get a new rad cap as bmw's are very farking emotinal about stuff like that some of the times.

-Charles

[paul crowhurst]

yes it was new and the make was nissen.