Loss of engine coolant

by Richard Russ in General Tech Discussion 12 years ago

I have a delema. I was checking the engine out (cold)and discovered that I had no antifreeze in the recovery bottle or the pressure tank on top of the engine.I didn't check the coolant before the last flight which had been with the winterization plates on and the engine oil temp was running 209 and CHT 250 which on the warm side (OAT 45 F) but nothing close to red line. This was just a check before heading for Sun-N-Fun. I added antifreeze to the both the pressure tank and the recovery tank and ran thye engine for about 10 minutes. On inspection I could find no evidence of a leak anywhere on the engine but I did see some dried water stains on the pressure tank below the pressure cap. The only thing I can come up with is maybe the pressure cap is not sealing properly. Has anyone run into this problem? I've ordered a new pressure cap since that is the only thing I can come up with that might cause the problem.
It would be nice to hear from anyone that may have experience a similar problem and their solution.

Thanks,
R Russ

Re: Loss of engine coolant

by mike hallam » 12 years ago

mike hallam

3 40 0

My 912 Ali rad has always had a tiny leak from the nylon plug area at the side/bottom of the tank where the drain tap is.

It proved impossible to seal with externally applied 'cures'/sealants as the pressure inside quickly lifts it off.

A new rad was considered four years ago but since then a dose of high quality USA sourced flakey ali rad sealant seems to keep it O.K for months up to a year at a time.

Pump seems happy so I'm contented.

There is a water temp. & water pressure gauge. The latter is a very good indication of water loss as the pressure will show fluctuations before the rad. liquid level has dropped much.

mike hallam.

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Re: Loss of engine coolant

by Roger Lee » 12 years ago

Roger Lee

125 5.11k 4.52k

Hi Richard,

Coolant leaks can sometimes be fleeting. The problem is that the high flow air coming into a cowl or an open air engine tends to blow the coolant off the leaky area and then when you look you see nothing or find it some place else. Fill the system then fly for an hour. Come down and pull the cowl. With the engine hot there will still be pressure in the cooling system, but no air flow to blow it off. Let the engine sit for 15 minutes or so and look for your leak. Common places are from under a hose, check all clamps. From around the 90 degree aluminum water tube that goes into the top of each head. Look at the base of those threads for a slight sign of a leak. Check the rear bottom of the engine at the water pump housing and around the radiator fittings. I have seen expansion tanks (on top of the engine) leak around the joint and bad expansion tank caps, but my money lies on a bad clamp or the 90 degree elbow . These seem to be the most common.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Loss of engine coolant

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