mark kibort

ok guys,

Over at scots diagnosing his over heat issues. putting in a new thermostat and there is no seal behind the thermostat like on Arron's 85 when i replaced it because the rubber was all chunking away . (not the "o" ring, but the rubber seal with steel insert that you need to chizzel out to get it out, and it seals the thermostat when the car gets hot to direct flow.) if it doesnt seal against anything (raw aluminum hole where the water flows out of), could that be the problem???? we always here that our cars cant run without a t-stat... and this could be like that issue if the seal was missing and it needs it to work under high flow high rpm conditions. as we told you , the car is perfect driving to and from the track and around town.

does the 82 euro engines need this seal in addition to the themostat O ring?
could this be the reason for overheat . maybe the new block we got didnt have this installed?? i dont know.

we are going to do the expansion bottle now,and maybe one of you guys can give us a hand .

thanks!! (from scots racing garage!) ha ha

Mk

mark kibort

what do you mean, " in t-stat housing"? so, if it is machined later, it would be obvious wouldnt it be? right now, there is a rough area at the back of the t stat housing. (where the t stat would press against the block area at temp )
it looks pretty rough, so its not machined as you are implying to accept a seal element.

this block is a euro 82 block. so, i guess they all dont have this seal in the rear of the t-stat housing?

thanks for the help. buttoning things up and dont want to put in the tstat if it needs that seal. if it doesnt, then our problems are either the cracked overflow bottle or a head gasket or cracked head. aahhhhhhh

mk

FlyingDog

The replacement seal I got for the t-stat housing is a plastic ring that's flared on the side toward the t-state with ribs on the outside the grab the t-stat housing. My old one looked okay, so I just left it.
http://www.mailordercentral.com/928i...106%20163%2000
That's it with the housing side facing up.

BIMMERMIKE

Could this be my overheating/runing hot problem??
When the rpm's are up and vehicle moving everything seemd to run okay, that is, temp indicator stays clsoe to first line. BUT when idling in hot weather and traffic it slowly creeps up to top line.
I replaced my t-stat and never noticed any other seal except for the o-ring in front housing side.
Should there be another seal in behind the t-stat??
btw: replaced viscous fan assembly with new one last year and it seemed to help

Tony

Youe need all seals and o-rings in that housing. The one that is "pressed" into the housing is often forgot about and is usually in very bad shape..hard..blistered and doesnt seal.
While you have the coolant out doing that it would be a good time to tap the bridge for an Autometer gauge. nice when you can look down and see you are running 195'F or 210.F etc etc. Dont trust the needle or the idiot light for over temp.
Ive got pics but not where i can DL right now.

mark kibort

I just got a confirmation that the older 928s, before 1983 dont have this seal.
This seal was pretty beat up in Arrons 85, but after we changed it, nothing really changed as far as overheating for him as well. it was a radiator issue.
scots we believe is either the expansion bottle crack, which bleeds off pressure, and then there is boiling maybe starting at the area closest near the cylinders. However, that may be a stretch as the water needs to get near 212 before boiling is an issue. Thats why im thinking its more of a cracked or warped head , or head gasket issue. You would think that the plugs, oil or water would show signs of this, but they dont. we havent done the test for the chemicals in the water to prove it, but that may be the next test.

its a puzzing case, as the problem is real bad, but only shows itself at the track, and nowhere else!
some how the water is boiling away during a 30min race, about 1-2 gallons. we are stumped!
let you know how the next set of tests go.

Thanks for the quick help on this one

m

SwayBar

Mark, after a session at Road America I pulled into the pits. I was standing beside the car taking my helmet off when I noticed coolant running out from under the car; WTF! To make a long story short, at home I topped off the coolant, put the cap on, but neglected to screw it all the way on till it 'locked'.

Out on the track there was plenty of air-flow through the radiator to remove heat from the coolant, but once off the track without the air-flow, the coolant boiled over out of the loose cap. A gallon and a half later, I was good-to-go, and with the cap tightened, never had the problem again. Of course, track-officials made sure I cleaned up the mess with their kitty-litter.

So it's possible that if the coolant recovery tank is cracked, or if pressure is allowed to escape from anywhere else, the end-result would be the same as a loose cap.

BIMMERMIKE

Pics would be nice
Thanks