low oil pressure on start up 1z engine

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green thing
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Location: Bradford on Avon

low oil pressure on start up 1z engine

Post by green thing »

I`ve been chasing this problem for over a year but I`ll try and be brief. I put the engine in my t25 and everthing was fine, (oil light went out in a couple of seconds) until the cambelt slipped, head knackered(300 miles into France). Returned with a partially recon head and brought it back. Over the next week the time taken for the oil light to go out went up to 5/6 seconds + a couple for the tappets to be quiet and whatever I`ve tried it will not improve.

I replaced the hydraulic tappets
then the oil pump(was given the top part of a new t4 pump, looks identical to the 1z pump - connected to the correct pick up pipe for the led over sump)
the turbo which was really oily and bearings had a lot of play
changed the oil a couple of times using vw 1z filters
checked the oil pressure at the back of the head, which showed good oil pressure when running but went down straight away when engine switched off(gauge could`ve been dodgey, it was an old one connected to some pipe)

At this point I was advised it was due to worn shells probably damaged when the head went so I bought a complete mk3 with 1z engine, 80,000 on the clock, it ran well in the car. Put the engine in but the problem was still there, the only bits I swapped over were:-

The turbo and manifold
oil pressure feed pipe to the turbo
the oil pressure swicth on the filter housing(which I now think, that I was sold the wrong one as it`s blue in colour)
sump
oil pump

I changed the oil again using an oil filter for the led over t25d engine, another turbo as the bearings were again very sloppy and pipes quite oily and, I had an oil feed pipe to the turbo made as I wasn`t convinced that the metal one was sealing properly against the filter housing.
I`ve noticed, that every time I top up the filter or when I separated the oil feed pipe to soften the washers and try to get a good seal, the first time I`ve started the engine the oil light goes out instantly and there is no tappet noise, but after a run and leaving it for a day the problem reappears. I`ve just found out that set in the oil filter housing, set in the chamber which feeds oil to the turbo there is either a pressure release vale(which I have in mine) or a restrictor(not sure what form that takes, I imagine it just protrudes into the chamber). In the t25d oil filter housing there is neither and in the t4 housing there is a tapped hole but again neither are present.

I know the latter is stood up but I`m wondering if just removed the pressure release valve, whether that would decrease the initial pressure to the turbo which might stop them from wearing out and, at the same time increase the initial pressure to the head curing my problem.

Could anyone please shed some light on this for me it`s driving me nuts and I`m reluctant to use the camper while the problem is still there.

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