Coolant blowout

[LARRYEBOYER]

I went flying today and when I landed I noticed coolant on the mast and some on the engine. I opened the release valve a little on the radiator cap and coolant squirted out the top of the overflow bottle on my RAF on the mast. I never experienced this before. I had not changed or added coolant since the summer. Some thing is pressurizing the system . Any experienced opinions?
One other thing, there is no coolant in the oil, but could I have a head gasket problem? would retorquing the heads work if head gasket ?

[Aussie_Paul]

I have had one head gasket leak with the same results as you Larrye. The gaskect leaked from the cylinder to the water jacket. I doubt re torquing the heads will be a fix, but there are people here that would me more knowledgeable tham I. You need to get each cylinder at top dead center and add compressed air (100psi I think), through an adapter to replace the spark plug, to the cylinder and see if bubbles come out the water. That way you might find which side to remove. There is one side that has this problem more than the other side but I can't remember which side. Hopefully others will pipe in Larrye.

Hope this helps.

Aussie paul.

[gyromike]

Don't forget to have a really big guy holding the prop when you pressure up the cylinder!!!

[Ron Marlett]

Most likley a blown head gasket but it could be a cylinder head crack. Do you have a compression gauge? Warm up the engine then remove all 4 spark plugs and run a compression test on it 1 cylinder at a time. Check the radiator cap for pressure buildup immediately after each test. SInce you are only pressurizing one cylinder at a time, this should lead you to the problem child. Once you find the low compression cylinder and or the cylinder providing pressure to the cooling system, remove the head and have it checked for cracks, warpage and pressure tested at a machine shop. If the head is fine, check that the block is true and try a new headgasket.

Ron

[CLS447]

I was flying with Larry on this flight. I suggested trying a new radiator cap first because the cap looked suspicious. If it is releasing pressure at less than the indicated 13lbs wouldn't this also overfill the expansion tank?

I also suggested checking the oil for coolant & checking the spark plug coloration.

On the RAF, should there be any coolant in the mast overflow tank when the engine is totally cooled down? If there is , how do you remove the rad cap without getting wet? What is the proper fill procedure for the RAF?

[Friendly]

Chris , I agree that the plugs are good indicators of a leaking gasket as well. The plug will usually appear very very clean. The porcelin will be white like right out of the box. A comparision of all four plugs would give an ideal of which cylinder if it is a head gasket problem. I don't think tighting a gasket will help if it is blown or begining to blow. If the vapor in the cylinder has escaped through the gasket upon combustion it usually burns a bit of the gasket and it will not be a thick as the rest of the gasket. you may run the risk of warping your heads. Not an expert, but I have been there.

[KenSandyEggo]

The overflow tank should be 1/3 full when cold. I add water through the overflow tank, but it is rarely needed. You'll always get a splurt when you remove the pressurized cap, even when cold.