I have a ''98 MGM. The last time I drove it everything was fine. Three days later I went to drive it and it started knocking when it started. I shut it off immediately. I tried 2 or 3 times and all it does is knock. It almost sounds as if it''s a rod or main bearing but don''t those usually go out when the engine is running? This knock started as soon as the engine started. Someone mentioned it could be the lovely plastic intake leaking water into the cylinders causing a compression knock. I''ve never heard of this. Does anyone have any knowledge of this or suggestions? Thank you for all your time.





Chris

this is a very hard one to answer because we do not know what the knock sounds like. can you do a video? yes you can get a cylinder knock but it sounds way different from a bearing knock. The cylinder knock is when the piston is desieling or an ignition knock. this can be cause from fluid in the poiston. is the oils a white color? is tghere white oil residue under the cap?

are you getting oil pressure? this will rule out the oil pump. is there water leaking around the front of the intake? I believe when these do leak they will not leak into the piston. what you are describing with the water is a head gasket. what the other person told you is that these cars are known for leaky intake manifolds that connect to the water inlet. this was becasue they were made of plactic. look for leaks but even if you do have one it is not why you will have this sound.

I have oil pressure. No water in the oil. The water level is low. I just filled it last week. Everything seems fine except for the knock. It was running fine when I parked it. The knock started as soon as I started it 3 days later. I have started to try and diagnose the problem but haven''t found anything yet.

well you can try this since it is already knocking. drain all the water from the radiator and the engine block. don''y worry it is safe if you do not let it get to hot. you can run a car for about 3-6 minutes safely without water or maybe even longer.


The reason i say drain the water is that for some reason it is leaking in the cylinder it will not be anymore if there is not water inthe system. This way you are not stuck with fixing a broken intake and it turns out to be the motor. if it stops knocking after there is not any water, then change the intake. if it is then change the oil, let it cool back down and try again. if it still is then the motor is bad. this is the best way if i don''y here the knock or look at the car to see what is wrong.

TO DO LIST:::


DRAIN ALL WATER FROM RADIATOR, BLOCK AND HEAT CORE


TRY AND SEE IF IT WORKS.


IF THERE IS STILL A KNOCK, DRAIN OIL AND REPLACE OIL WITH NEW OIL INCASE IT WAS CONTAINIMATED WITH WATER.


IF THERE IS STILL A KNOCK THE THE CAR MOTOR IS BAD.


IF THE KNOCK STOPPED AFTER ONE OF THE ABOVE STEPS THEN CHANGE THE INTAKE.