i think im going to take my multi air off to check but the only cylider that had air coming out of it was 4 because its intake valves were open either way im going to have to replace the head gasket hopefully its just that because a head gasket kit it a lot cheaper than valves
yea ill do more testing looking at the top of the intake valves with my eye-crometer and they look like theyre all properly seated, ill do a leak down test and pump some compressed air in. id assume my head bolts are fine but ill check those the only annoying thing is to get to them you have to pull the camshaft housing but ill prbably do that eventually after i dig into it more. im starting to lean towards blown headgasket inbetween cylinders because while one cylinder is going up and compressing another one is going down causing a vacuum and that might cause the 0 psi compression. idk if that makes senseInteresting to see the operation in above videos.
My thoughts are a bit more basic, with regards to the initial leak down test, assuming as is said that the multair unit cannot hold valves down on it's own, then if valve timing is correct and engine set at TDC on the firing stroke for that cylinder and crank /cam locked up, then if air pressure via the leak down test is applied, then if air is leaking out it can only be through a faulty multiair unit/valves jammed open or head gasket between the adjoining cylinder.
Normally I would have inlet manifold off and be able to see if air was escaping past the inlet valves on the cylinder being tested directly into those inlet ports related to that cylinder, so if no air escaping into ports, but air escaping into adjoining cylinder then one must assume an issue with the head gasket into that next cylinder.
Apart from exhaust valves on that cylinder also, unless they have been eliminated obviously.
I try to break things down for simplicity, so in effect an engine is basically just a pump with pistons and valves, to trace where the loss is going.
Is it possible to do the leak down test with the multiair/brick unit off the vehicle or does it hold the cylinder head tight also?
If possible and exhaust valve cam lobes are closed on firing stroke on that cylinder that is locked up to do the leakdown test, so all inlet and exhaust valves are supposedly shut on that cylinder it should be possible to determine if any air loss is via head gasket or actual engine valves in cylinder head.
none stuck in the open position but if i have it sitting upside down if i push one down it doesnt return bacck , it feels like theres no spring and its just hydraulically driven
Just a little concerned when you mention plugging other cylinders when testing cylinder one etc, that maybe you are not following the correct guide for doing the leak test and maybe getting odd results.
But even with poor seal, they wouldn't give you 0 psi on compression test, would they?
i wasnt doing a leakdown test i was joust pumping in compressed air cause in theory with no camshaft all the valves should be closed air should only be escaping through the rings i can see about doing a proper leakdown test today
With valve issue you can get 0 psi unlike a piston which even with broken rings will still have some slight sealing effect in my experience. Even more so if just doing a compression test.
Are the manifolds off when you are doing this test so that you can see if the escaping air is going out of a suspect valve or are you just going by the percentages?
) But What I call a compression test is with the valves all working and connected , all the spark plugs out and the compression test gauge screwed into the spark plug hole of the cylinder being tested and the engine cranked over with a good battery roughly ten revolutions, some people also hold accelerator pedal down, but largely irrelavant on modern ECU controlled vehicles. I would expect on a good engine reading ideally around 180psi. on each cylinder.yea this last one with the pictures was a leakdown test the tested i got was a little weird cause it only wabnted about 30psi though i dint think my air compressor could keep up with 100+psi i had it hooked up to a specific cylinder and i didnt have it locked at tdc for each cylinder i jost had it locked at tdc for cylinder 1 and 4 with the timing tool so the crank wouldnt move, i dont have my intake/exhaust out yet because its so annoying lol but i can hear the air escaping out of the throttle body.Are the manifolds off when you are doing this test so that you can see if the escaping air is going out of a suspect valve or are you just going by the percentages?
I am getting a little confused (not that that takes much with me.
What I call a "leak test" is as I have described earlier, again with all spark plugs out, but with the cylinder being tested at Top Dead Centre and the valves closed on that cylinder, with the engine /crankshaft locked in that position preventing the engine from moving, high pressure air is introduced via the spark plug adaptor (I use 150 psi) and all exits from the engine are checked for air escaping, valves/pistons etc. This test is then repeated with each other cylinder. In general terms I would expect a slight loss past the pistons and no where else, so nothing past valves into ports or gaskets into adjoining cylinders etc.
Incidentally I ensure no air leaks from the high pressure hoses and the air compressor, well away from the test so that it is easier to actually hear where air is escaping.
Hard to pin point exactly the problem then.
I mean, doesn’t air coming out of the intake point to the valves not seating? I think what happened is that when this all went down, my oil pump didn’t seize, but the resistance increased dramatically and that broke the keyway off my timing pulley. I thought it didn’t slip, but there was nothing preventing it from rotating besides the crank bolt. I figured I got away without any problems, but now I’m thinking the pistons might have given the valves a little kiss.Hard to pin point exactly the problem then.
It does sound like valve issues especially if your 100psi compressor was only showing 30psi presumably from the leakage..
It does sound like valve issues especially if your 100psi compressor was only showing 30psi presumably from the leakage..
If the keyway sheared then it certainly points to some sort of hard contact.
The suspicion was always there re valve and piston contact , but you had no obvious signs when using the camera and felt the valves were closing I recall.
Always easier with manifolds off to detect leak at ports, but air loss from throttle body certainly looks like it.
It will be good to get to the bottom of it.
Normally an hour spent with the leak off test is fairly conclusive, although it takes a little longer on diesels due to removing injectors or heater plugs to do the test.
Probably hard to get oil through inlet ports to show much
Yea I'm definitely going to take the manifolds off it's just a bit involved I feel like my might have a tiny bend in them, also that leak down tester was weird it was like hook it up to an air compressor until the leak down gauge reads 0 then hook it up to a cylinder. I would have much rather just had 2 pressure gauges and a regulator so I could see more accurately.It does sound like valve issues especially if your 100psi compressor was only showing 30psi presumably from the leakage..
If the keyway sheared then it certainly points to some sort of hard contact.
The suspicion was always there re valve and piston contact , but you had no obvious signs when using the camera and felt the valves were closing I recall.
Always easier with manifolds off to detect leak at ports, but air loss from throttle body certainly looks like it.
It will be good to get to the bottom of it.
Normally an hour spent with the leak off test is fairly conclusive, although it takes a little longer on diesels due to removing injectors or heater plugs to do the test.
Probably hard to get oil through inlet ports to show much.
