Variable oil pressure
Discussion
Hi guys,
My Chim oil pressure gauge reads 30psi some days and 60 other days. Some times the pressure will rise as the revs rise - other times it stays the same at idle as at 5000rpm.
Engine has been completely rebuilt and is top condition but keeping an eye on the oil pressure gauge is pointless unless I can get it to tell me what the oil pressure going round the engine is.
I had an oil pressure test done and was told both it and the gauge were fine but I can't live with these mostly random readings from the gauge.
Before I replace everything (randomly) - where is the most likely point for me to start please?
Thanks for any helpful (and humourous) advice.
My Chim oil pressure gauge reads 30psi some days and 60 other days. Some times the pressure will rise as the revs rise - other times it stays the same at idle as at 5000rpm.
Engine has been completely rebuilt and is top condition but keeping an eye on the oil pressure gauge is pointless unless I can get it to tell me what the oil pressure going round the engine is.
I had an oil pressure test done and was told both it and the gauge were fine but I can't live with these mostly random readings from the gauge.
Before I replace everything (randomly) - where is the most likely point for me to start please?
Thanks for any helpful (and humourous) advice.
I would guess that the garage just stuck a calibrated mechanical gauge into your oilways and checked that the gauge agreed with your dash of a range of engine conditions..
The pressure relief valve is a piston with a spring behind it, when too much pressure is seen it pushes back and bleeds oil back to the pump inlet. Its purpose is to limit the pressure to a certain level, but it is possible yours may be sticking. Generally pressure will be higher as you rev the engine, and it will then be restricted to say 60/70psi by the relief valve. If it sticks open you have no pressure, and if it is slow closing you will see strange things...
The other common problem is loose pick up pipes where they mate top the block and crap blocking the pick up gauze, both in the sump. Its like a kind of partial blockage or syphon coming out of the liquid IYSWIM.. That can occur as the engine revs change in the early stages I guess. These are more common faults, not heard much about the pressure relief valves, maybe the serp ones are behaving better
Dave
The pressure relief valve is a piston with a spring behind it, when too much pressure is seen it pushes back and bleeds oil back to the pump inlet. Its purpose is to limit the pressure to a certain level, but it is possible yours may be sticking. Generally pressure will be higher as you rev the engine, and it will then be restricted to say 60/70psi by the relief valve. If it sticks open you have no pressure, and if it is slow closing you will see strange things...
The other common problem is loose pick up pipes where they mate top the block and crap blocking the pick up gauze, both in the sump. Its like a kind of partial blockage or syphon coming out of the liquid IYSWIM.. That can occur as the engine revs change in the early stages I guess. These are more common faults, not heard much about the pressure relief valves, maybe the serp ones are behaving better
Dave
As Dave says the pressure relief valves can stick on the pre-serp engines, so if that's what you have then it may be worth taking the valve out and giving it a light polish and treating it to a new spring.
Also you don't say what temperatures this is happening at as oil pressure will obvously reduce when the oil temp is good and hot, I would only be concerned it it starts making less than 1.2Bar at idle and less than 2.5 Bar at 3Krpm when hot.
Matt
Also you don't say what temperatures this is happening at as oil pressure will obvously reduce when the oil temp is good and hot, I would only be concerned it it starts making less than 1.2Bar at idle and less than 2.5 Bar at 3Krpm when hot.
Matt
Dave and Matt, thanks for that.
It's on a late '96 serp which has had all the sludge cleaned out and rebuilt with all new seals and filters etc so wouldn't've thought it was a pick up problem.
I know the pressure should rise from idle as it goes up through the revs. I've had the actual pressure checked with an external gauge and also the gauge in the car and both pronounced to be working fine. However, out on the road the gauge seems to show randomly varying pressures which bear no relation to the engine speed!
As you are both pointing me to the pressure release valve spring I'll get that out and probably replace it with a new spring/valve and see if what that does.
Will have to get it next week now and report back... "oh please don't" I hear you say!
Regards David
It's on a late '96 serp which has had all the sludge cleaned out and rebuilt with all new seals and filters etc so wouldn't've thought it was a pick up problem.
I know the pressure should rise from idle as it goes up through the revs. I've had the actual pressure checked with an external gauge and also the gauge in the car and both pronounced to be working fine. However, out on the road the gauge seems to show randomly varying pressures which bear no relation to the engine speed!
As you are both pointing me to the pressure release valve spring I'll get that out and probably replace it with a new spring/valve and see if what that does.
Will have to get it next week now and report back... "oh please don't" I hear you say!
Regards David
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