M42club.com - Home of the BMW E30/E36 318i/iS

DISCUSSION => Engine + Driveline => Topic started by: PumpItUp on May 11, 2010, 05:01:38 AM

Title: Thermostat. How many ponies will I lose without this hole
Post by: PumpItUp on May 11, 2010, 05:01:38 AM

I just took out the oem Wahler thermostat and it has a hole at the top.
My replacement Behr does not, it has an arrow. I never understood the point of the dot or arrow (if it does not have a hole). Should I drill a hole to make it have that "breathing" feature? FYI the new one is 88 degrees while the old one was probably the 92. Maybe that plays a role or maybe its that these thermostat holes are f'ing useless and Wahler hasn't caught on :confused:

The metal flange which connects to the 2 radiator hoses has 2 bumps in front of where the thermostat sits, whats that about?? and does it play a role with 'the hole'

I guess what I'm asking is, has the hole been proven to be useful, or is it only something from the 90s. And since I don't have the hole, and I'll probably be too lazy to drive one in, whats the point of a "this on top" arrow indicator. Would the thermostat work regardless of how I inserted it :confused:

Title: Thermostat. How many ponies will I lose without this hole
Post by: flyinglizard on May 11, 2010, 07:22:12 AM

It is an air bleed hole.   I always drill; one on the top side of the stat. MM

Title: Thermostat. How many ponies will I lose without this hole
Post by: cristimm on May 11, 2010, 09:34:21 AM

Me too, that little hole makes bleeding a lot easier. :)

Title: Thermostat. How many ponies will I lose without this hole
Post by: PumpItUp on May 11, 2010, 06:02:07 PM

a lot? if thats so why didn't behr include one, considering how annoying this car, (and their radiator) is to bleed. and the thermostat cost more than the wahler, which was sold out

Title: Thermostat. How many ponies will I lose without this hole
Post by: flyinglizard on May 11, 2010, 08:37:43 PM

If you look real close around the  T stat gasket area, there is a very small groove  around the top, to aid bleeding. Often RTV fills this up.
 MM

Title: Thermostat. How many ponies will I lose without this hole
Post by: PumpItUp on May 11, 2010, 09:38:38 PM

i was patient and waited 24hrs until rtv hardened, then cleaned out areas like that. also i listened to you guys and went ahead and drilled the hole. hope it helps

Title: Thermostat. How many ponies will I lose without this hole
Post by: Big Ian on May 23, 2010, 06:56:40 AM

Hi sorry to ask on someone else's thread but can someone tell me what size of hole needs to be drilled through the thermostat to help with the bleeding?
i just fitted a new thermostat to my E30 318iS and then had to remove it for now as when i filled the cooling system back up no water would pass the thermostat.
will a bleeder hole help this problem?

Title: Thermostat. How many ponies will I lose without this hole
Post by: cristimm on May 23, 2010, 09:28:02 AM

1mm is enough and yes it will help bleeding a lot.