I need some help with a coolant system issue......
Finally had a mechanic check for leaks in the coolant system after i have been topping up from Min to Max every 3 months or so (small leak?).....the next day I drove the car for the 1st part of the day and then later, steam! Opened the hood and coolant was percolating out of the overflow reservoir cap....gurgling like a geyser...there were no over heat light indicator and the temp guage was at its usually...could replacing the cap be the only culprit....Any ideas?

If you weren't watching it and filled the coolant up to the max level when the engine was cold, it would do that once it got warm and the fluid expanded. But if you're topping up every three months or so, you've got a small leak in the system somewhere. Crawl under it and check the hose at the bottom of the radiator. I flushed the radiator once on my 97 GLT, filled up with new coolant, drove it, parked it, and had a tiny puddle of green fluid on my garage floor the next day, which I noticed when I pulled it out. I really tightened the hose clamp when I reconnected the hose, but not hard enough. A lot of pressure builds in that system when the engine is warm, and it will force it's way past your hose clamps if you don't really tighten them down. Always double and triple check for a week after you change coolant just to make sure you have no hose leaks. Keep in mind though, that the radiator hose connector is plastic, so don't get too heavy handed with the screw driver. Dick

Tnx Dick....i am going to put more fluid in today cold and check to see what happens.

A low pressure cap could do that. While you are at it, also check the water pump for weepage.
Klaus
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98 V70Rawd(108Kmi), 95 854T(88K mi), 75 164E(173K mi)

Tnx claus...what do I check for with the water pump? is it obvious if it is not working properly?

Yes. Take the cover off of the timing belt and shine a light on the external part of the water pump - bottom, closest to the firewall. Look for any green stuff. You could also start the car up, with the cover, etc out of the way and listen for noise coming from the pump housing. Usually, the sighting of antifreeze is a signal to replace the pump and seals.

A shop can do a pressure test. You could also verify that the cap on the overflow bottle is nice and tight. If the shop did indeed add antifreeze while the engine was hot, it will overflow, check the level only when the engine is cold.

Lets just hope the manifold isn't warped and you are loosing coolant into your oil or burning it. It smells sweet at the tailpipe when the engine is hot.

Klaus
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98 V70Rawd(108Kmi), 95 854T(88K mi), 75 164E(173K mi)