The V8 Owners Forum -

Hi All, I'm new to this forum and so pleased that I have found it, I need some V8 help. I have recently bought a kit car with a Rover V8 3.5 engine fitted and I'm not sure if the oil pressure is OK.

When I start the vehicle from cold the oil pressure gauge doesn't really move at all for several minutes and there is a distinct rattle from the top end. After a few minutes the oil pressure gauge eventually goes up to 3 bar and the engine stops rattling. After it has warmed up the pressure drops to approx 1 bar. When starting the engine from hot, again the same thing, it takes several minutes for the oil pressure to pick and the rattle to stop. I think the oil pressure is OK once it has picked up, but why does it take so long, is this normal for this type of engine? Is there anything to worry about, I've tried changing the oil but this made no difference. The engine has only covered approx 4K miles since it was re-built.

Please advise

Mike n Helen

You need to look into what is wrong as something is for sure. If your using 20/50 oil then either the pump is worn (gears or casing) or the relief valve is dodgy. I would say check your gauge but if the engine is rattling then there isn't any oil pressure for sure. You really don't want to run the engine like that as the crank wont be getting any oil.

Just as an after thought when you changed the oil did you change the filter? I have had bad filters before that caused some odd looking problems.

My thoughts would have been the relief valve stuck open and draining all the oil out of the pump ? Does it happen if u switch it off and restart it after ...say 2 minutes? john

Mike n Helen wrote:When I start the vehicle from cold the oil pressure gauge doesn't really move at all for several minutes and there is a distinct rattle from the top end. After a few minutes the oil pressure gauge eventually goes up to 3 bar and the engine stops rattling. After it has warmed up the pressure drops to approx 1 bar.

These pressures sound about right (mine is 2 bar cold, 1.5 bar hot), but the pressure should come up straight away. Any rattling from the tappets should stop in a few seconds really.

First thing I'd check is the oil pressure relief valve, they can stick sometimes. Maybe it's sticking open?

Jeff

The pressure relief valves do have a habit of sticking. The fix is to fit a tadpole valve instead (from JE engineering), however my tadpole sticks closed giving me over 60PSI when cold.

I would dismantle the oil pump and check it all out, including checking the valve for smooth movement.

Chris.

The pressure relief valve is sounding favourite at the moment, I have previously changed the oil and filter but no joy.

Next question may sound really stupid, but please bear with me I'm new to V8 engines, where is the pressure relief valve? I've checked my trusty Haynes manual this evening, which didn't help as my car has got a remote oil filter system, forgot to mention that earlier. Don't seem to be able to see where it is, any suggestions?

Thanks,

Mike n Helen

follow the oil lines back to the engine front cover. They will either screw into a sandwich plate instead of where a filter would go or they will go into a proper cast pump bottom. If it looks like a sandwich plate, above that is the pump bottom and on that is a large hex plug, behind that is the valve. If its a proper cast pump bottom then the plug will be on that.

katanaman wrote:follow the oil lines back to the engine front cover. They will either screw into a sandwich plate instead of where a filter would go or they will go into a proper cast pump bottom. If it looks like a sandwich plate, above that is the pump bottom and on that is a large hex plug, behind that is the valve. If its a proper cast pump bottom then the plug will be on that.

It's a proper cast one, but I coudn't see it when I had a quick look this evening, a job for tomorrow night on the ramps I think.

Mike n Helen

Hi,

Does your car have a remote filter or just the normal engine mounted filter ?

If it's the remote type, and mounted too high, it can cause oil drain back . The rattle will be zero pressure until the filter fills up. Also check that the connections are not reversed.

Normally if the oil pressure relief valve sticks open , you will not be able to get any pressure, so I have my doubts about it being faulty.
Regards
Jim

I've got a remote oil filter, mounted high up (higher than the water pump), and I have no problems with drain back. But then my oil filter has a one way valve in it.

I don't know how you get an oil filter with a one way valve in it, but all the ones I've had recently have had one.

Chris.

ChrisJC wrote:I've got a remote oil filter, mounted high up (higher than the water pump), and I have no problems with drain back. But then my oil filter has a one way valve in it.

I don't know how you get an oil filter with a one way valve in it, but all the ones I've had recently have had one.

Chris.

I read an interesting article about two very expensive racing engines self destructing because the remote oil filter had been plumbed back to front, causing zero oil flow to the motor, because the filter check valve was obviously back to front too.

OK an update from tonight. The oil filter is mounted at about the same level of the water pump so I removed the bracket and lowered, started the engine, let it run for a while and no difference.

With the oil filter back where it should be I removed the pressure relief valve from the cover (it's a Mocal part). Noticed some scoring on the max diameter of the ball, but could also see where the seat of the valve had been making good contact. I dressed up the score marks and put it all back together and still nothing.

Where next???


Mike n Helen

Oh, a ball type is a tadpole valve which is non standard. It sounds like there's been trouble in the past then possibly.

Can you measure the clearances inside the pump as per haynes manual? You have to take the end off the pump and measure between the rotors and the timing cover.

If everything seems to be in order, it might be worth removing the sump and checking the main bearings / big ends to see if they're a bit tired and hence allowing excess oil to leak out....

Chris.

A further update from tonights efforts. Bought a new filter from the main stealers and some fresh 20/50 oil. Changed these again and still nothing. What I do know for sure is that there is no oil being picked up as the filter, after running the car for a minute or so, still hasn't filled with oil, it sounds empty when you tap it.

I'll get a new oil pump gasket tomorrow and strip that out when I get an hour.

Mike n Helen

this sounds like you might have either a failed pickup pipe gasket or something is blocking the actual pickup pipe. Both of these are in the sump am afraid. Could also be a bad pump gasket like you have mentioned or even front cover gasket. Either way it sounds like your pump could be drawing air, it also sounds like it needs primed. I would invest in a priming stick and investigate with that other than running your engine with no oil pressure like your doing just now. At least with with a priming stick you cant damage your engine but you will soon know if your pumping oil.