Mike Frye

Tom,

I agree if the T-stat is bad or the seal is missing. But disagree with the suggestion that a lower temp t-stat is going to fix his temp situation when sitting in traffic. He said his original diagnosis/question was based on the T-stat being the 'stock' temp and he wanted to go lower. My assertion is that if the stock t-stat is working as advertised and he's having this problem, the issue isn't going to be solved by changing to a lower temp t-stat.

SteveG

There is a small hole, I guess less than 1 mm, through the T-stat. Do you mount with this at the top, side, bottom, or does it matter?

newworld

the small hole is the jiggle pin, should be at 12 oclock. it is an air bleeder.

my question is this, when i installed the rear seal, and tstat, i can see a gap, so i assume the coolant when cold circulates thru the rear seal and the block and not the rad.

when temp is reached then the tstat expands? and closes that gap and seals with the rear seal?

Tom. M

Yep...that's the way it works..

Tom. M

True on the surface...but when I put my lower temp t-stat in...the car ran cooler (gauge) in all conditions I drove.. I don't sit much in traffic, and yes, when sitting in stop and go traffic in Wichita last OCIC (100 degrees plus), the temp gauge was where it was before I added the lower temp tstat....

I like the lower temp t-stat simply because it starts working sooner and the "ramp" up to operating temperature is slowed (for my usual driving patterns).

For colder environments, this might not be good...especially if you have a shorter drive..

Mike Frye

Is it possible that something else changed when you did that T-stat change? You had to drain the coolant system, maybe you flushed it too? Did you clean out the radiator fins or find some leaves in there and pull them out? Maybe just the act of draining the coolant and refilling it dislodged some obstruction from the radiator or some coolant passage in the engine? Maybe the old Tstat wasn't opening all the way and the new one does?

I just want to make sure anyone following along understands the function of properly functioning T-stats of two different temps is exactly the same when fully warmed up, or at least they should be.

Tom. M

Im not disputing that... but the way I look at the cooling system is like this (poor analogy, but best I can think of at the moment)...two pots of water on the stove..one 2 quarts...the other 4 quarts.....both burners on high..

the one with less water (e.g. stock thermostat that stays closed longer keeping the volume of coolant in the block longer)...will boil first.....

the one with more water will take longer to boil....(t-stat forces water in block to mix with cooler water in rad sooner giving a cooling effect from both volume and the efficiency of the rad)...

but in the end... you are correct... and both pots end up boiling

69gaugeman

Likely the changing of that rear seal would cause your car to run cooler. That seal is a bypass from the rad so it would bypass some of the rad coolant and just recirculate it if the seal was not working properly.

Bilal928S4

The Porsche engineers designed the engine to run at a certain operating engine temperature. This final temperature is the most efficient and environment friendly. Why would you want the engine to take longer to get to it's preferred/designed operating temperature?

Tom. M

I'm guessing that their final preferred/designed operating temperature was more suited to fuel economy ...over performance.. But just a SWAG..

69gaugeman

The hotter an internal combustion engine is, the more efficient it is. Unfortunately we have to live with materials that melt before the efficiency is 100%. Being more efficient means a cleaner burn. If it wasn't for cold starts the cat would not be needed at all as, when the engine is hot and running normally it burns clean. The cat 'burns' unburnt fuel (think WOT or start-up) and other than that it runs perfect.

sstrickstein

Ok so today after replacing my t stat I drove the car to work. Same route and conditions. The highway temps were much lower and the in town stoplight never saw the 2/3 mark. Since I have a 944 and it behaves the same after a complete drivetrain rebuild, I will call this one done. I also consulted with an expert here In Phoenix, Jack at Stutgart Southwest on Tempe. He told me he has seen some cars with them and some without, He has rarely seen any difference in the operation. He did suggest any further work should revolve around the Clutch fan. I read a article online about rebuilding the clutch fan. I am going to look into this as well. However, I wont replace the Fan clutch, I would install a Electric fan kit instead.

Hilton

Early cars don't have it (I think it was only fitted from '84? certainly 83 "Euro" don't have it)

jeff spahn

Why would you put a flush kit in the car? Simply open the block drains and your coolant will be all out.

crushingday

Does my '78 have this rear seal?

I was under the impression that it may have been introduced in a later model