QuestionQUESTION: My son and I are working on restoring a 72 mgb. It will run smoothly and then start clanking - very iradically. At the same time the temp will approach the hot zone -- even with the thermostat removed. Does it need a new water pump???
Thanks, dave
ANSWER: Hi David,
What you describe narrows the problem down to 1000 things so you need to do some testing. First thing you should not run the engine without a thermostat in it. That will not make it run cooler and can make it run even hotter.
A "clanking" noise is useless information unless you can raise the hood and listen to where the noise is coming from.
To check a water pump look under the front center of the pump to see if it is dripping any coolant then loosen the belt and feel the pulley for any up/down play and rotate the pulley to see if it feels smooth. The only other thing that can go wrong with a water pump is the impeller come loose inside and the only way you can check that is to check coolant flow and that can be checked roughly by removing the thermostat cover and thermostat and disable the ignition and spin the starter to see if you have good coolant flow out of the housing. This should be done with the engine hot as a loose impeller may be ok and tight on the shaft when cold. This is very unusual on MG so it would be a least likely fault.
Look at the tail pipe when you rev the engine to see if you see any white smoke which would indicate a blown head gasket. Also with the engine cold, remove the white wire with a black tracer from the coil and open the coolant expansion tank and with a flash light look at the coolant level while someone spins the starter. If you see bubbles or the coolant level raise, that is an indication of a blown head gasket also.
Let me know,
Howard
---------- FOLLOW-UP ----------
QUESTION: Howard,
It looked like water is flowing from the upper hose (back to the radiator = so the water pump appears to be working. Also we have not seen any leakage. The oil looks ok, not milkly and the exhaust looks ok (no white smoke). The plugs look sooty - but it is run rich with the choke out.. I did a compression test 150, 145, 143,143 -- the 72 does not have an expansion tank. -- the "clanking" seems to be coming from the bell housing and is very random --- it even happened when the engine was cold..
.
AnswerHi David,
The compression test shows ok, now look at the oil pressure hot and cold. If you show 25 to 35 PSI or above at idle when the oil is hot and 50 PSI or above hot then I would suspect either a loose flywheel or even something with the pressure plate.
One other test you might look at is to put a pry bar against the front pulley and force it to the rear of the car. Then watch it very closely with a light while someone depresses the clutch pedal. You should not see any movement. If you do it means the thrust bearings are bad. Not common on MG but can happen and will make noise.
The normal preliminary test of a loose flywheel is to let the engine idle very slowly and blip the throttle a few times and listen for a heavy knock. (sounds very much like a main bearing knock but the oil pressure test separates the two causes)
let me know,
Howard
