mystery coolant leak

[dutchalfaguy]

Hi all,
'92 Spider:
Stopped at smog station aftwer a 4 mile drive. all well on board.
The car ran idle wfor about 10 minutes while the tech filled in forms. He started the visual and discovered a drip of coolant from the front (about in the middle). I could not see anything obvious around pump, hoses, radiator. Overflow tank level about halfway F&E, but tank seemed pressurized. He didn't want to do the smog because of the malfunction.
Filled Coolant bottle completely, drove home.
Left car running, bottle still full. Car ran idle for 20 min, throught several fan cycles, but not a trace of leakage.
All I can think of is the filler cap doesn't vent out, builds pressure, causes a leak?

Any experience/thoughts?

Johan

[jclark]

Just gotta check all the hoses, make sure it's not the water pump leaking, the overflow tank is supposed to be at whatever airpressure your engine bay is...( that is, *no* extra pressure, thank you ).

[vf31rhill]

Sounds like correct position for water pump leak out of the weep hole in the bottom of the pump housing, but could be number of things including lower radiartor hose or connection and coolant recovery tank overflow. You will just have to closely check a lot of items all of which are hard to see and located in a very crowded engine compartment. Good Luck, Robert

[Tifosi]

Any reason to think that it might have just been the car before yours?

ie: did anyone actually see it drip off yours, or was it just a spot on the floor?

Still your overflow shouldn't have pressure as Jeff said.

[Gubi]

Pressure in the overflow tank is normal with a hot car. That's what the valve in the cap on the overflow tank is for: it holds pressure up to a safety limit (0.7 bar, I think?) and then vents.

These cars have pressurized cooling systems. The pressure boosts the boiling point of the coolant and helps resist boil-over.

[dutchalfaguy]

Thanks all for the replies.
Unfortunately, I witnessed the leaking, and it was my puddle allright.

Over the weekend, I will go over the hoses more seriously.

Q: If there is not to be pressure in the overflow bottle, how does this cooling system build pressure, as it has no radiator cap/pressure valve, but a bottle cap with a valve?
Has anyone had a bottle cap that refused to open & vent, causing an excessive pesure in the system? Or, am I just in denial?

I'll report back
Johan

[Gubi]

Quote:

Originally Posted by dutchalfaguy Has anyone had a bottle cap that refused to open & vent, causing an excessive pesure in the system? Or, am I just in denial?

[vf31rhill]

Actually I think I mis-spoke about coolant recovery overflow. The theory I believe is that expansion in the radiartor/cooling system overflows into the recovery tank. then, when the cooling system cools off, the liquid contracts and this draws the liquid in the recovery tank back into the system. I am at work now but will verify this on my own 88 tomorrow. Some vehicles have a recovery tank overflow pipe and some do not. The Alfa dos not, I am thinking now, Will verify in the mortning.
Robert

[John M]

Just to clarify and reiterate what Tom (aka Gubi) has said, the reservoir is pressurized on a series 4 and is self bleeding. Different beast from the earlier spiders. Check the weep hole on the water pump. Seal internally goes bad and it starts dripping behind the pulley......sometimes when running....sometimes when parked.......not necessarily all the time. And for the four fingered fellows, be sure to check with the engine OFF.

Best Regards,
John M