Best way to check if an engines healthy?

[xlr8_87]

gday guys,


I've been looking at a couple of cars, one of which i'll be buying as a donor for my car.
All i care about is the health of the engine and gearbox, so whats the best way to check them?
I've driven both, they both seem smooth and gears change very easily.

Would the best way be to take it to a mechanic? what should i get them to test?

Any info would be great

thanks,
Rob

[pandaman]

A compression test is a good start, tells you if pressure is escaping from the cylinders due to crappy rings, valve seats, gaskets etc.. If one or more of the cylinders has low compression then don't buy the car. A vacuum gauge can also be used to assess the health of an engine, can't remember which readings mean what, but there are a fair few pages on it around the place.

[Tree cutter]

Hook a vacuum guage up to the engine and run it . There are heaps of tests you can do on an engine with a vacuum guage. It will tell you if you have worn valve guides, leaky valves,worn rings,blown head gasket and even if it is just out of tune. A good vacuum guage will come with a chart that tells you what the various readings mean. You could also do a compression test on the engine and hook an oil pressure guage up to it to check the condition of the bearings. Take the radiator cap off and check the colour of the coolant,if it is rusty looking dont touch it because the coolant has not been changed regularly and you could be up for big repair bills if the cooling system gets corrosion through it and leaks. Check the colour of the engine and gearbox oil. Black engine oil can mean worn rings or valve guides or way overdue for service. White or milky engine oil means a possible cracked head or blown head gasket.If the gearbox changes gears without crunching and doesn't whine in any gears it should be OK. Undo the filler plug on the gearbox aand dip your finger in the hole to make sure it is full and the oil is a nice clean colour.

[J_D]

Here is a website showing how to test for engine problems using a vac guage.

things that the vacuum gauge can be good for:
http://www.users.bigpond.com/ergoff/vac1.htm

[xlr8_87]

cheers guys, i think i'll get them checked out by a mechanic, and make sure they test the mentioned things