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Hi brains trust.
My good friend and part-time car destroyer has palmed his 99 VY to me for troubleshooting. It was "overheating after a short distance and then running rough". Car has 300,000km on it, new radiator about 50,000km ago.
After checking thermostat (which was opening, but only just, was replaced), thermofans (fine), water pump, etc, have isolated the problem to a cracked and leaking plastic heater-water control tap. Few questions:
1. There is what looks like bleed valve on top of the thermostat housing. I seem to recall this is to ensure there are no air pockets in the water jacket. What is the procedure, after I replace various bits, for re-filling the system with coolant and ensuring it has not air pockets?
2. The bigger problem is I suspect my friend drove the car once too often or too far without water and has damaged the motor. It has a steady and consistent "miss" (sounds to be running on 5 cylinders), even when cold, when idling, when under power, etc. Hoping it was an electrical problem, I put a timing light on all six spark-plug leads, and got a steady and consistent signal on each of them. So preliminary diagnosis, given the overheating, would suggest he may have damaged the motor. I thought the first and easiest check would be to do a compression test. Is there any problem with doing this one cylinder at a time with the car running, but disconnecting the relevant spark-plug lead at the coil end? Also, what compression would I expect, bearing in mind its done 300,000 km?
Thanks in advance.
Matty Q |
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Over heating and running rough.
Head gasket fella. Have you pulled the plugs out and had a look at them??
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Not yet. What should I be looking for with the spark plugs? A compression test should prove a stuffed head gasket, yes? |
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quote:
Originally posted by Matty Q
Not yet. What should I be looking for with the spark plugs? A compression test should prove a stuffed head gasket, yes?
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Have you compression tested it yet??
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quote:
Originally posted by Matty Q
Not yet. What should I be looking for with the spark plugs? A compression test should prove a stuffed head gasket, yes?
Yes, the plugs may show some evidence of a blown head gasket but there are two better methods. 1. Remove all the spark plugs & pressurise the cooling system, using a hand pump at the radiator cap fitting. Leave it pressurised for 20-30 minutes & then crank the engine, with the starter. Water/coolant will spew out of the offending cylinders plug hole. 2. A chemical tester placed over the radiator cap hole will sense the presence of any combustion gases in the cooling system, due to a blown head gasket or cracked head. When doing a compression test of EFI cars make sure you remove the fuel pump fuse or relay to prevent petrol spraying into the cylinders while the engine is being cranked. Its probably an even a better idea to disable both fuel & spark to prevent any disasters. Dr Terry. |
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Thanks Dr Terry et al.
The water leak is a heater control tap. I did do a compression test (albeit after reading your email, Dr Terry), thought Id posted them earlier, but something went wrong. Results were:
Right bank: 1=135psi, 3=100psi, 5=175psi
Left banks: 2=162psi, 4=106psi, 6=118psi
So looks like the motors pretty sad, although am I correct in saying doesnt look like an outright blown head gasket? Am wondering if this wound casue the engine to miss consistently...?
mq |
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By the way, spark plugs look all the same and fine. |
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The fact that you say it has done 300,000 hard Ks doesnt make the thing sound real good either.
The compression test results are all over the place.
Might be time to trade up.
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