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Does anyone know where i can locate a dummy spark plug tester so i can attach an air line to it to fill the chambers with compressed air. The reason for this is i have a car with a suspect head gasket (loosing water but no leaks). Ive compression tested it but all are fine at 175 each. This test will show an increase in water level or even air bubbles in header tank if the head gasket has gone. Seen them before but cant locate 1 where i am.
Yeah, it will, and if your don't chain the car down it'll shoot clean out the garage too! But...........your choice. The procedure is called a leakdown test and without an open pressure guage also connected to the cylinder your checking there is no real way of telling whats happening anyway. Use an old spark plug, smash out the ceramic, break of the electrode and have someone weld a pipe, or better still a connection for compressed air onto it. Personaly I'd give it a miss and have it leak tested by someone with the right equiptment. That being a plastic tube with a rubber cone that fits into the radiator or header tank of the vehicle you want to test and filled with fluid that turns yellow if there is ANY sign of combustion gasses in the water, SIMPLE, reliable, easy and a lt less dangerous. The test you mention, was never really useful anyway because an engine isn't designed to be able to sustain pressure within the combustion chamber for anything other than the instant it takes to combust during a cycle. The engine would have to be set up on TDC on the firing stroke on every cylinder you want to test, which is a pain int the arse at the very least cos each time you test a cylinder the engine will have to be jammed in that position, which you may find difficult unless you also make up a tool to lock the flywheel too. Save yourself the grief and take it for an estimate, let THEM find the problem even if you plan to fix it yourself.
BTW, Compression testing isn't about the maximum compression achieved, its about finding out the difference between the highest and lowest pressure attained across all cylinders. The difference between highest cyl and lowest cyl should be less than 10%, in other words, the lowest should be at least 90% of the highest. A healthy engine should produce compression that is around 18 >19 X's the compression ratio.
yeh
Easiest and quickest way to test for a blown head gasket is to go to an mot station, and ask them to do a gas test on the coolant bottle or rad.
This involves sniffing the gasses inside the coolant bottle when the engine is at opp temp and running, but you have to be carefull not to sniff any water into the prob as this will damage the gas bench.
If the gasket is away, you will get a high reading of hydrocarbons, "unburnt fuel"
There shouldn't be any hydrocarbons in the coolant system, and a blown gasket will show up fairly quickly.
Very quick and accurate test, will only take 30 seconds to carry out and should only cost you the cost of a pint if the guy is half decent.
Gordon
A cylinder leakage test.Quote:
Originally Posted by Hybrid
Yes the engine will have to be set up on TDC, But there is no need to lock it, TDC refers to top DEAD centre, when the piston is at TDC, the piston can not be forced down because the forces applied are pushing directly down on to the crank, not at an angle, so it can not move.
Easy to set up one you have the timing mark for number one cylinder, use a thin piece of welding wire and slowly turn the crank untill it is at it's highest point, (go back and forth a few degrees to make sure).
test NO.1 then if you know the firing order of the engine ususally 1342, go to no.3 and do the same and so on. . .
If the engine rotates after the air line is fitted then it wasn't quite TDC.
This test will show leakage around the rings, head gasket from adjecent ports, burnt or not seating valves, or head/gasket into waterway.
This kit/test came with some of the older crypton tuner machines, but a home made one is just as good.
Test 2 The block test,
This is the Funnel that goes on to the expansion tank, and you fill with dye, when the presence of combustion gasses is there the dye changes colour.
Test 3
The easiest, a cooling system presure check. A false cap or big "plug" goes in to the cooling system filler neck/tank and is pumped to put the cooling system under pressure, showing leaks from pipes, joints water pump ect. Best used from cold with the spark plugs out, pump up to the blow off presure usually on the filler cap, leave for 10 mins and see if the gauge goes down to indicated a loss of pressure (a leak) crank the engine and see if water comes out of the spark plug holes, if no external leaks are visible.
If you do make your own cylinder leakage test use a presure regulator and start low and increse presure up.
hope this helps someone
Ted.