Start by checking to see if your Aux fan works (m)
Does the clutch fan work OK?
aux fan=pusher fan? andoverheating v8 m62 98 model
My main fan behind the rad with rthe fan clutch works but I could never get the electric "pusher Fan" to work. When should this come on? How do I check it? I understand that there are 2 types 3 pin and 4 pin.
I am having overheating probs. Is it true that the original thermostat housing is plastic and prone to damage so its replaced my aluminium housing.
Can I just buy the thermostat and gasket and keep the original old plastic housing?
V8 should have all metal t-stat housing (m)
I've posted a few times how to troubleshoot the Aux (Pusher) fan in front of the radiator. You should have a 3 speed fan.
You either have bad resistors, a bad fan motor, or bad relays.
Use search to find it, it was a long post.
Sounds like you have not completed the >>
bleeding operation. It would appear that there is still air in the system. The failure of the aux fan will not cause the heater to turn cold.
Here is the procedure for the V8:
Bleed cooling system via Jim Cash
First - coolant should never be to the "top" of the expansion tank.
I think there are 2 versions of the expansion tank but I suspect they both have the float and indicator stick. Assuming you have the stick indicator it the top of it should never be above the lip of the filler opening rim.
That "expansion" tank is supposed to be mostly air - leaving room for the coolant to expand and compress the air as the coolant heats up.
If you overfill it then it will come out the escape valve and suck air back in - air in the system can cause levels to vary and bring on the alarm.
Bleed the system with the following proceedure - and it is necessary to raise the front end of the 6 cyl cars to do this
Cooling system bleed procedure – M62 engine (E39 – 97 version)
- with cold car
- top up coolant to proper level.
- leave rad cap loose
This stage bleeds air trapped in the heater system.
- turn on ignition switch to position 2 (no start)
- set temperature selectors on the climate control to max temp.
- manually set the fan speed to low (lower end of speed range)
- start engine (check that climate settings have not changed)
- after 5-10 seconds of running rev the engine 3-4 times to about 2500 RPM - hold
there for about 5 seconds each time.
- shut off engine (should not run for much longer than about 30 seconds - you just want
to shut if off before it starts to generate any heat and expand the coolant).
- inspect the coolant level and top up again if necessary.
- tighten the coolant fill cap.
This stage bleeds air from the engine, rad and fill tank.
- now warm up the engine (drive a bit if you wish)
- with engine running CAREFULLY / SLOWLY open the bleed screw. Hold a rag around the area to prevent any excess splashing. Keep the screwdriver in the slot of the bleed screw so you can close it quickly.
- you should have some air/steam escape - progressing to some bubbles of coolant.
- as soon as it progresses to the stage where you are seeing liquid coolant come out then close the bleed screw. Do not over tighten - it is all plastic threads and you can easily turn too far at which point the screw jumps back a thread and you have to re-tighten. Just make it snug with all coolant stopped.
- when the car is cold again re-check the coolant level and top up again if necessary.
You may have to repeat the bleed procedure 1 or 2 more times over the next week. Can "probably" skip the stage for the cold start bleeding of the heater system.
If the level continues to fall below the correct level then have the system fully pressure tested - explaining to your service manager what you have already done.
It is very important that all leaks be sealed so that the system can operate at full pressure. The engine computer is programmed to keep the coolant temp at about 108C at "most" times (there are exceptions) and the only way it can maintain that temp is if the pressure can be maintained - system fully sealed.
Ed in San Jose. BMW CCA member since 1987 (Nr. 62319). Golden Gate Chapter. '97 540i 6 speed. Build Date 3/97. Aspensilber over Aubergine leather.
Re: Temperature fluctuating
Thanks guys, I'll be able to work on it again tomorrow. I'll check out the aux fan and re-bleed.'97 540i auto
Sticky thermostat? If you changed it out last (m)
& there was air in the system, it would've given you issues months ago, so I'd say thermostat.
Re: Temperature fluctuating
If the heater temp gets cold the problem isn't the main fan, aux fan or the thermostat, IMO
His problem is that the gauge reads too hot while the heater goes cold. My first guesses at this combination of symptoms is a bleeding problem, headgasket problem (leading to continuous bleeding problems) or a water pump problem.
Without the "heater going cold" symptom, then all of the usual fan checks should be done starting with the main fan.
The t-stat and it's housing should come a 1 piece(
It isn't displayed properly here, the t-stat really isn't removable from it's housing on the left side in the link below.
Re: The t-stat and it's housing should come a 1 piece(
Is there a way to test if it is the thermostat thats causing the overheating Jim?
Stick it in a pan of water with a thermometer (m)
Put it on the stove and watch what temp it opens up at. Do it a few times to make sure it doesn't stick.
whole thing? t-stat inc housing?
Yes, the t-stat doesn't come out of the housing (m
superb! what about the electrical connectorin h20?
Not a problem, dry it out B4 U put it back in car
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Thats a big 10-4 Jim. many thanks!!
Re: Temperature fluctuating
Problem solved! I re-bled the system, purged some air and now the gauge is dead center and rock solid. Thank you for your help, saved me spending $80 on a thermostat that I didn't need.'97 540i auto