PDA

View Full Version : Don't buy a Fan Clutch until you check this...



Visions
06-24-2013, 09:23 AM
92 735i
I had the classic fan clutch symptoms... Over heating when slowing down and at stop... Put car in neutral and rev it up and the temp goes back down.

The issue wasn't the fan clutch... it was that tiny bleeder hose coming off the top of the radiator... I don't know the official name for it...

When the car is cool... remove the coolant expansion tank cap... look inside the neck of the expansion tank... you'll see a tiny hole... start the car... when the thermostat opens you should see a small flow of coolant and usually bubbles... if you don't its clogged and its not letting air out...

For me , as soon as I loosed up the clamp and pulled the hose off, the coolant level rapidly dropped which tells me there was an air pocket... it was like if you draw fluid up a straw and you put your finger on the straw to hold the liquid in the straw...

From what I can tell the tiny hole isn't inline directly with that hose so you can't shove something thru it from the hose end and come out that hole.... if you look closely there is space between where coolant sits then it comes thru that hole... I just took a tiny wire and put thru both ends and it cleared out whatever was causing the issue... the hole is so tiny I'm sure it could happen again if there is something floating in there... I'm not sure if it would be wise to make the hole larger...

Anyway clearing this out solved the over heating issue that had the symptoms of the fan clutch going bad...

Hope this helps someone...
Good luck!

shogun
06-25-2013, 02:55 AM
Thanks for sharing.
Gale has a good write up with pics on this
page_2 (http://www.nmia.com/~dgnrg/page_19.htm)

Visions
06-25-2013, 08:24 AM
Thanks for sharing.
Gale has a good write up with pics on this
page_2 (http://www.nmia.com/~dgnrg/page_19.htm)

Shogun, you and your site have helped me fix every issue I've ever had... so its only right that I share too...

BMWFatherFigure
02-09-2014, 07:52 AM
Thanks for the tip. You never stop learning.........

shogun
02-09-2014, 09:24 AM
the square hole above the top o-ring, this is the discharge from the pressure relief valve
http://www.bimmerboard.com/members/rv8flyboy/original/radcap.jpg