heinrich

We never see hot days here. Well ... we have recently. And on 90-degree days, I have discovered that I tend to lose just a dash of coolant via the overflow (I can smell it) on hard acceleration. I'd say I've lost maybe a cup of fluid over 3 weeks of daily hard driving. Any thoughts? The cap is new. Reservoir and hoses new. Engine temperature is pretty constant and well within spec.

heinrich

Kinda sounds like the cap huh.

heinrich

Actually I was thinking maybe I needed to have a little less coolant and a little more water ... so I did that. Will see what happens.

abbzer0

Sorry I can't help you there.. But perhaps if you keep posting replies to yourself, you may eventually figure it out! LOL

the flyin' scotsman

Heinrich..............when was the anti-freeze last changed? These engines are designed to operate with the correct ratio of water and a/f. Check to see what temp its good for and if in doubt change it; remember to drain the block and the rad and refill with the correct mix.

Sounds as if the your having boil over on shutdown; thats when the coolant will be at its warmest after a hard run in hot temps...............are the rad fans staying on after engine off?..........if not there good be a problem there.

heinrich

Malcolm, not shutdown. High rev, kicking butt, on the freeway. Engine was replaced in the last 10k miles. New fluids.

PorKen

Lean mixture?

heinrich

Hmmm ... on an S4 that isn't easy to do. Remember, temps stay constant as indicated, nevber approaching anything high-ish. It's more like a mechanical pressure rish or maybe an instant localised heat rush, but there should then be a residual temp rise indicated ...

mcholdfast

[QUOTE=are the rad fans staying on after engine off?..........if not there good be a problem there.[/QUOTE]

My fans run for a second or two after shutdown. Should they run longer? I recall that my Corrados' fans would run for a while after shutdown, but they also had an electric aux. water pump to circulate the coolant after shutdown as well. It seemed like a good idea, but the aux. pumps were prone to failure and leaks.

mark kibort

what is the cap rating anyway. 16psi???

Bill Ball

Can you see evidence around the cap? Should be green/crusty stuff. Otherwise, make sure it isn't a hose clamp loose somewhere.

Mrmerlin

Hi Heinrich where is the coolant level when cold? It does sound like a bad cap my car runs right at the seam on the side of the tank and just below when it is cold

bigs

H -

First the stupid comment. How much coolant is in your reservoir when cold? Is it possible you just have too much and it overflows when the engine heats up?

If you've just replaced your engine, could it be the water pump? Maybe a gasket leak?

Have you ever tried running the car hard for a while, then pulling immediately off into a parking lot, shutting 'er down, and checking under the hood or under the car to see if you can still see something leaking and where it's coming from? (Don't catch yourself in the electric fan!) Or maybe if you kept the engine running and blipped the throttle from under the hood you'd see the source of the leak...

Big Dave

Put some newspaper down on the garage floor, flog the car, park it and watch where the drips are. At least you can zero in on where it's coming from (left/right/front/back).

I had the same problem, and it turned out I was missing 2 gaskets, 1 at the rear of each head.

SharkSkin

H, get a pressure tester that attaches to the bleed hose on top of the radiator. You can make one with little more than a gauge, a tire valve, some hose and a few fittings -- all available at the hardware store -- plus a bicycle pump. Pump it up and see if the cap relieves pressure per rating or at some lower pressure. While you're at it you can check for leaks.