I finally got my 1990 GT running after being in storage for 3 years and it ran pretty well but has a very strange coolant problem. I drove it twice on both trips I would fill the coolant to the line and after ONE mile the low coolant and hot engine warning light came on. When I opened the hood the coolant reservoir was empty.

So I put the car on the driveway, let everything cool down for 30 min. Then I filled the reservoir and let it sit for 30 minutes. When I came bac the level had dropped an inch. I started the car, and let it idle, the level held, then after the engine had warmed up all of a sudden I watch the entire reservoir drain in 10 seconds. Right in front of my eyes.

I turned off the engine, looked under the car, looked all around and no sign of the coolant? So over the course of two one mile drives and an idle on the driveway, I have burned through 3 gallons of coolant with no sign of it?

The were no white clouds or any color smoke with the exhaust. I checked the oil and besides being 3 years old I didn't see any foam or froth

Any thoughts? I am stumped!!!!

 

It's not unusual to go through that process after a coolant change. I had to heat cycle and refill 3 or 4 times last change. This would also be the case if you lost coolant 3 years ago. As the air bubbles dissipate, the system takes more fluid. This is assuming that you really don't have a hidden internal or external leak. Remember a pin hole leak in the system can give off coolant as a vapor and you don't see anything. Do you smell coolant?
Good luck,
Dave

 

what was the last thing you fixed?
The cooling system holds 4 gallons
The system is self bleeding.
The water pump is turned by the timing belt.
does the engine run smooth when you start the engine?
Is there any smoke from the tailpipe?
Are there any white crusty deposits on the right hand tank of the radiator?
When was the last time the heater control valve was replaced?

 

That may the issue. So When I first got the car started today, I had topped off the coolant reservoir, but had forgot to put the cap back on the reservoir (I know, a complete bonehead mistake, I was doing too many things at once ). After a while white smoke was billowing from under the hood, I pulled over and popped the hood, and sure enough without the cap on the reservoir the boiling coolant was bubbling and splashing out.

When I got home I topped it off in the reservoir, and then went for the mile drive I describe above. If the system really takes 4 gallons, then maybe I still have a lot more to replace, and what I am seeing if the car ingesting the fluid form the reservoir into the engine???

 

Good advice above. If you haven't put in almost four gallons it isn't full yet.

One thing you can do is to idle the car with the heater on until the fans come on. Then let it cool down for several hours. (Overnight is best.) Then check the reservoir level. If you do this three times in a row and the level still drops you have a leak (or you still don't have four gallons of coolant in the system.)

However, it doesn't seem - from your post - that you had an empty cooling system to start with? Stan's first question is important.

Once you are sure that you've put four gallons into it, if the level still drops after a heat cycle you have a problem.

Post back with your findings when you have them.

 

You might want to ensure that you're not leaking coolant into the V of the block. Look as well as you can under the intake. If coolant is pooled there, it might be that the water bridge is leaking.

 

Wonder if it was drained for storage. Wonder if thermostat seized at the same time, inhibiting the refill.

 

from the additional info provided,
my last question is very important,
as it sounds like your HCV short hose blew.

replace the cap,
and the short hose
and the HCV

The 928 is self bleeding, no tricks are needed to fill it.