I always check the water level in the wp neck and the AST. And of course I do the same with the overflow tank. Last week the wp neck and the AST were full of water, and the overflow tank was in the full mark. But today the AST and the wp seems to have less water, and the mark in the overflow tank is upper. Is this a problem? Will it be the same than before, or the oferflow tank will keep "stealing" water from the others?

 

This is simple. You have a leak in the cooling system that is cancelling out the thermo-siphon effect of the cooling system. SO when the system cools, you are sucking air instead of coolant from the expansion tank back into the cooling system. I would replace your caps on the fill and the AST, and carefully check all the little hoses that go from the AST.

 

Absolutely correct, but there is one other possible cause: a pinched/collapsed hose or other blockage that acts like a check valve, letting water flow (under slight pressure) to the OF tank, but will not let it flow back (under slight vacuum) to the engine.

Dave

 

^ very true. Good post.

 

That's an strange thing. I have already replaced all the coolant hoses (last week!) and the AST is a brand new pettit racing aluminium AST. I've already checked the hoses from and to the AST, and I can't see any leak from there.
The only thing is that the wp neck cap is old, and doesn't seems to be in a perfect shape. I prefer thinking that the hoses are in a good shape since they're new, and I can't see water on the floor or on any part of the engine, so...

Well, until I find the problem, should I fill with coolant the AST and the WP, although this water fill finish in the overflow tank?

 

Did you happen to replace the line from the AST to the overflow resovoir? I had this problem a few years ago and the problem turned out to be the cap on the overflow container (not the one that you fill, the one that connects to the AST, or the neck if you have deleted the AST). The cap was flopping around and it wasn't holding the bottom of the tube below the coolant level. When the car cooled off it would just suck in air.

Happy hunting..

 

And one more: could this finish emptying the water in my cooling system and overheating???? Should I run w¡th my car in this way??

 

If you check it at the fill cap cold each time before you start it, and top it up, the worst you will do is overfill the overflow tank which could then overflow and make a mess. It should not harm the engine unless the level in the engine gets too low, and you will prevent that if you re-fill each time before you start up cold.

The basic problem may originate from the filler neck that is beat up, and doesn't seal, allowing air instead of water to be drawn back.

Dave

 

I have a similar problem if i fill the main coolant it seems to go down 3 inches into the tube then i fill up wait 20 seconds and it goes down again, it will keep doing this forever, i assume it is leaking out of the overflow valve in the radiator filler, but im not sure as i have never seen a puddle, do you think this is the same problem?

 

I'm confused - what do you mean by "main coolant" and by "overflow valve in the radiator filler?"

And the water has to go somewhere - it can't just disappear...

Dave

 

Dave or Baja,
Could there be one more possibility....a coolant seal issue?

 

I hope not! I own a brand new engine with 3000 miles on it, and has never been overheated. Anyway, I don't miss coolant. All the coolant missing in the AST and the wp neck is in the overflow tank. So I will check as you've told me the cap in the overflow bottom, the one that connects to the AST. Let's hope this will solve the problem.

 

Sgtblue - Yes, it IS a possibility, but with his low-mileage engine I was not seriously considering it. For the record, as some of us have found out the hard way, an engine with a compromised coolant 'O' ring will allow combustion pressure to force coolant into the overflow tank and out of the car. If enough coolant is lost, then there isn't enough to
"suck back into the system" and you will experience the, "****...I have to add about a cup of coolant a day" syndrome. Essentially the symptoms are very similar, as far as the coolant loss goes, as to a leaking cap or other air leaks in the system that defeat the thermosiphon effect.
Coolant loss like the orginal poster indicates is always HOPEFULLY an air leak, we cross our fingers and make dark, secret midnight ritual offerings to the Rotary Gods and HOPE it isn't a bad 'O' ring.

 

Double-check that AST for nice secure hose connections. When I was running the pettit, there was one hose that didn't fit as well as I thought, and needed some extra consideration to get it to seal properly.

dave

 

Yes, certainly, but we were looking for the most likely and easily fixable things first, hoping that coolant seals were not the issue.

Dave

 

I will let you know as I can check it. By the way, thanks... again

 

I was talking about the one north west of the ast. i can endlessly fill this, but it never goes down more than 6 inches down tha tube. mystery hey