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MG MGA - Coolant Loss - Why?

Back in October I had the lower radiator hose crack and caught the temperature rising on the highway, again in the morning on the way to work. Towed the car home, replace all of the hoses and refilled. Checked the radiator a number of times after that and no water consumption (I have a B overflow/recovery tank installed). Then this morning I managed to lose most of the coolant on my way to work and am trying to figure out why. This time I didn't notice it quite as fast the the temp gauge was pinned against the oil pressure needle. Had it towed home and went off to work. Got home this evening and filled the radiator expecting to find water dripping out from somewhere. Not a drop. Started the engine and let it idle. After a while the water level started to slowly drop with an occasional large bubble belching up out of the filler pipe. Still no water dripping onto the drive. Without further testing I have to assume that the problem is either: 1) a blown head gasket; 2) a cracked head; or 3) a cracked block. One last bit of information is that this engine had been rebuilt just before I bought the car and had developed excessive blow-by in the #1 cylinder. Oh yes, and the measured compression when I got it was 185 psi on all four cylinders. Still there on 2 through 4 when the blowby problem was diagnosed.

Question: Any guesses on which of the three failures is the problem, and any easy way to check? I assume that pulling the engine is probably called for in any case.

Suggestions? Comments?

Thanks

Larry
58 A 1500
Larry Hallanger

You could try pressurizing the rad and see if it holds air pressure or if it provokes a visible or audible leak
Art

Yup, pressure test first. Fill fluid to top, apply 10 psi, and wait. If the pressure does not hold, look for leaks. Check all hose connections, the water pump, heater valve, and edges of the head gasket. If it dribbles on the floor count yourself lucky, fix a clamp or valve or have the radiator repaired.

If it does not dribble on the floor, you are about to be pulling the head, because it's leaking inside. Remove spark plugs and spin it over with the starter to see which cylinder spits fluid. Most of the time it will be a blown head gasket. Much more rarely a cracked head. Almost never a cracked block (unless the coolant froze).
Barney Gaylord

As I'm sitting here in 20 degree weather and looking at my salt encrusted every day car, I really feel bad for you Larry! Any way I wonder what kind of waterpump you have? Some of those new aluminum pumps have plastic impellers on them that when hot the impeller can spin on the shaft causing all kinds of trouble,and when cool every thing is fine, something to think about if no others have any ideas. Hope it's something simple Larry, Good luck
gary starr

Looks like it is head pulling time. The test that I ran this evening was with the radiator caps off and the level went down under this condition with nothing visibly dripping on the ground. And there were occasional large air bubbles "belching" out the filler neck. These symptoms don't seem to correspond to a leaking fitting, hose, etc.

Thanks for the inputs.

Larry

Larry Hallanger

Larry- is the exhaust white?
gil

Have you checked your oil to see if it looks like snot? I would still do the pressure test, and sparkplug test.

The coolant has to go somewhere- it has to be in the sump (looks like snot), in the cylinders (white smoke at the tail pipe or fuid coming out of the plug hole) or, on the ground.

Good luck!
j
JohnB

Larry, I hope there is no serious damage. I have a similar problem with my car, but I believe that it is related to air pockets in the head or block or even heater matrix. When I fill the radiator, even with the engine running I occasionally get a bubble back out of the neck, and I lose fluid out the overflow when I'm driving. The car doesn't overheat, and shows no signs of any problem in the engine. It's been this way for several years now. Try lifting the front of the car with a jack and stands and then fill the system. This might help remove any bubbles or air pockets that will expand when the engine heats up and force coolant out. Also make sure you open up the heater valve and circulate coolant through the matrix to eliminate any air pockets there.
Bill Young

This thread was discussed on 10/02/2006

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