fbgh2o

I have been having a bizarre issue. The car never overheats, but runs hotter at highway speed. It will literally drop 5C when I exist the highway (from 93C to 88C) almost immediately. A pressure test revealed no issues.

I recently saw a post here about the "proper" position for the expansion tank cap. Essentially, the 4 protrusions from the cap should be at 0, 90, 180 and 270 degrees and there is a detent at the correct position.

So I went to check my new cap (the aftermarket one that my indie installed when mine failed last summer). It was not at the correct position and was probably out by about 70 degrees. I could not hand tighten it much, but with a set of channel locks, I was able to turn close to 90 degrees (which is too far).

Initial position was the green line. Correct position (?) is the red lines. The green arrow is what I was able to turn it.



Is this likely the source of my issue? Thoughts appreciated. Thanks

Macster

If you used a channel lock to tighten the cap you might have damaged the cap or worse, the coolant tank.

The cap is the issue (even if it is not damaged from the tightening), not its position.

I have seen nothing about the cap's bumps having to be aligned with anything. (I just got the 996 Essential ... book and have not gone through it completely yet, but I have the factory manuals for a Boxster and Turbo and there is nothing in there about the cap having to be aligned with anything in the coolant replacement/checking sections.)

My advice is get a proper new coolant cap (part # that ends in 02 or 03 or 04) and toss that aftermarket cap (and to be safe the channel lock pliers) and hope the tank's not cracked.

After you replace the cap keep a very close eye on the coolant level.

Also, how do you know the coolant temp drops 5C?

And 93C (199F) to 88C (190F) is just 9 degs. F. Not even that 199F temp is scary and a 9F temp drop ain't much at all.

Sincerely,

Macster.

fbgh2o

Thanks Macster. No evidence of cracking or damage. I should have said, I don't have a ton of strength in my hand due to an old injury. I needed them to remove the old cap when it leaked.

Both the climate control hack and my Durametric have shown the same results.

Macster

Hehehe. I too use pliers more often now than I used to. No injury thank goodness, but my hand strength is not what it used to be when I worked on cars alot.

I can type about a zillion words a minute but have a struggle to remove my cars' radiator caps.

Ok. While the temp drop is real it is not significant.

I can't explain it but I also can't think of how the cap could affect the temperature of the coolant. The cap is there (among other reasons) to keep the cooling system under pressure (once it is hot enough to create pressure). It is the pressure that most affects the temp at which the coolant boils.

An engine being asked to move a 3000+lb car down the road at speed is generating some heat. Once that load is removed and if the fans are running the coolant temp will drop a bit pretty quick. I don't want to say that what you see is normal but it might be.

Sincerley,

Macster.

Sincerely,

Macster.

Ahsai

No idea about what causes your problem but it looks like coolant is leaking from the bolts of the bleeder valve?