fraggle

I overheated my motor once on the way to SITM2008. Still struggling with it at FRENZY.

New rad, new waterpump, new thermostat, new seal behind the thermostat.

Short trips (<4mi) are still OK. Longer ones are borderline, especially if I work the throttle bit.

Last couple of weeks the motor seems to be losing coolant somewhere - ~1/2" lower than the seam in the tank a week, maybe less.

I can see no evidence of coolant in the oil, nor visa-versa, but I haven't dumped the system yet (I need to fix my real daily driver first).

Any advice here would help. It's been a long frustrating time here with this problem.

V-Fib

When you say no coolant in the oil, don't look on the dipstick. Look in the oil strainer. Mine never showed on the dipstick on either of my blown headgaskets. Hope it's something simple and inexpensive.

SeanR

What year?

JHowell37

You need to check your cooling system to see if it holds pressure.

IcemanG17

Are you sure the gauge is accurate.......they have been known to be a bit erratic....try taking a temp reading right at the thermostat cover...

Also what is the blend of coolant-water.....do you use water wetter?

So 928's just seem to run hotter than others....my 88 runs VERY cool...typically the 1st white line (170F or so)....vs my track shark that runs HOT....nearly the 2nd white line (about 190F), but I think the headers increase underhood temps quite a bit....

hacker-pschorr

Good point

I was helping out with a friends 928 this past spring. I mis-understood which 50 gallon barrel to use to fill up the cooling system in his 928. I was pouring in straight coolant (no water). It ran hot on a 40 degree night going down the highway at 70mph. Dumped out half the fluid, poured in water - bingo, problem solved.

fraggle

Sorry: it is an '87s4.

I'm running 75/20/5 water:coolant:water wetter. 75C thermostat, C&R rad, uber-fans from 928 specialists.

At the frenzy I checked it against several other cars after a good run with an ir gauge. It was running 84C+ behind the thermostat housing, where other cars ranged from 71C to 79C. I can't even touch anything under the hood after longish drives.

Temps don't really stablize if I'm driving, temps just keep rising until I get spooked, back off the throttle and turn on the heat. It almost acts like there is a flow restriction to the rad somewhere. When I rev the motor I can see the radiator hoses stiffen up a bit so I know there's some flow.

I'm just really frustrated! I did a full tbelt job and replaced everything in response to this with no real change in performance.

VehiGAZ

2 cents worth... test the t-stat - put it in a pot of water on the stove, monitor water temp as it rises and see if it's really opening when it is supposed to.

fraggle

Already tested. I compared the old 83C one to the new 75C one. It opened earlier and wider than the old one.

Am I in denial? I don't want to tear the heads off.

ew928

Was the cooling system pressure tested?
As in replace coolant tank cap with cap that has pressure gauge on it and a valve to pump up the cooling system to see what pressure it holds up to.


How old/cracked is the coolant overflow tank.
Mine cracked when I looked at it wrong.
Must be real difficult for the Germans to spec a translucent plastic that can take underhood temp. (Coolant tank on my ex-Audi also cracked, and that for me is a trend)

123quattro

It is either leaking coolant via a bad cap or tank, or it's head gaskets. You have replaced everything else.

IcemanG17

Did you pressure test the cap??? Of course if it pops when you open it, its probably fine......

Heres an out there idea......change the springs to the oil thermostat.....typically this results in low oil pressure warnings on hot restarts...BUT I did hear it can drop running temps a little bit......plus the parts are cheap so why not?

If my track shark keeps running hot I will try it at the next oil change...

fraggle

Haven't pressure tested the cap, but I do get a good hiss when I crack it.

If I really test the system, what kind of numbers am I looking for?

tailpipe

i had the pump impeller come loose onthe pump shaft on me took me abit to find it just tackedit back on with the tig welder

paul

jthwan22

Try the Advance Auto parts tool loaner for Rad pressure tester. Pump it up to 14psi and see if it hold the pressure. They may also have an adapter in the box to test the cap.