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MG MGB Technical - head gasket failed?

I recently replaced the head gasket on my 78 roadster with a Payen gasket. The other day I noticed that coolant was leaking from the front crossmember and across the fromt cover. Coolant was apparently originating from the water pump. There is no white smoke coming from the tail pipe. Is it likely that the head gasket failed (or worse)? By the way, what is the pressure rating supposed to be of the coolant recovery cap?

George
G.E. Bulwinkle

about 13#-V
vem myers

With a mirror check the drain hole in the bottom of the water pump. It"s just behind the pulley at 6 o"clock. This is where the coolant will be leaking if it"s the pump
jim soutar

George. The factory pressure cap was of 15 psi rating (Bentley manual, 1975-80, page 60). The cap is the same as used on small block Chevy engines (and others) in the 1970's and 80's, but may not be available in a 15 psi rating at your local auto parts store. Somewhere between 12 and 15 psi should work fine.

As Jim notes, it sounds more like a water pump or hose connection problem than a head gasket problem. With a head gasket problem, the most common point of leakage is on the right side of the engine near cylinders two and three. Leakage in the front part of the engine, especially below the water pump, would tend to indicate a problem with the water pump--if it were the cylinder head gasket you would see coolant on top of the water pump and all over it.

Hoses are easiest to check--just make sure they are in good condition and clamped down properly. Next, check the tightness of the bolts holding the water pump to the engine block. If the hoses are in good condition and tightly clamped and the bolts holding the water pump are secure, you would have to pull off the water pump and replace it to see if the leak would stop. (I do not know of any test for the water pump off the car.)

In stead of doing all of these things to try to find where the problem(s) is/are in a hit or miss sequence, have the cooling system pressure tested. A hand pump with a dial gauge and a flex line ending in a radiator cap connection is attached to the overflow tank and the system pressurized to the rated capacity of the pressure cap--15 psi in this case. This tests the capacity of the system to hold the rated pressure and, when it cannot hold it, will allow you to see any external coolant leakage is drips from the point of leakage. You can also use the cooling system pressure tester to test out your radiator cap to see if it will hold to its rated pressure and make a good seal. Any good mechanic should have this piece of test equipment and should not charge a great deal for performing the test.

Les
Les Bengtson

OK I replaced the water pump and gasket. That seemed to solve the problem. Head gasket is hoding well and no evidence of a head crack. Thanks!
G.E. Bulwinkle

Have you retorqued the cylinder heat since replacing the head gasket? If you do retorque it, don't forget to check your valve clearances afterwards.
Derek Nicholson

Yes I retorqued the head. Thanks for reminding me to adjust the valve clearance.
G.E. Bulwinkle

This thread was discussed between 16/02/2009 and 01/03/2009

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