ZZ4 oil pressure problem

[menostig]

Hi,

I wonder if anyone has seen this kind of thing before. The oil pressure reading on the (Ultima) gauge was 3bar at cold idle (1200rpm), then 2.5-4bar during a normal 40min traffic-ridden drive, with 2.5 bar at the warming idle when we stopped. Then it idled on the drive while we faffed about, and I noticed after a few minutes that the pressure settled well under 1 bar, I'd say about 0.75 of a bar - this at 750rpm. the oil temperature and water temperature were normal (70? and 85 respectivly). RealSteel said it should be more like 2 bar at warm idle.

There was some black crappy oil smudged around both cam-cover breathers, where I think the O rings weep a little. There was also a finger wipe's worth of black oil on the block under the exhaust manifold. No drips anywhere though, and the nice gold oil was in the right place on the dipstick.

Perhaps the best course of action is to find someone with a mechanical gauge to test oil pressure, although any other ideas / anyone seen this kind of inconsistent gauge reading ?

Thanks,
Roger.

[gdr]

My oil pressure is pretty stable, varying only as you would expect due to temperature and RPM, never less than 2 bar at hot idle. I am no SBC expert but 0.75 bar got to be too low. Worth checking with mechanical gauge - you can sometimes get earthing problems with the electrical senders although unlikely. If gauge OK, suspect an internal problem unfortunately.

[Allen-GTR]

Agree. If you do not have a gauge/sending unit problem, then you probably have an oil pump problem. Not the end of the world, as its (fairly) easily accessable with the pan off.

I would think the factory (or VDO) could give you the expected voltages for the oil pressure gauge. That would be the easy thing to check first. Also, is the fitting for the sender sealed well? Both at the block and the sending unit? Possible bad sending unit?

If that fails, then it would be time to pull the oil pan.... I would take a look at the pickup. Is it loose? (way back when, they were known to fall out of the pump, but most pump manufacturers have a clip or some other method of securing it. I have seen them even brazed onto the pump.) Is it the right length for the oil pan?

Just a few suggestions... Hope that helps...

Allen

[menostig]

Mechanical gauge showed much better results at hot:

RPM ELECTRIC GAUGE CAP GAUGE
750 0.6bar 1.5bar
1000 1.0bar 2.2bar
3500 3.0bar 4.0bar
4000 3.2bar 4.5bar
4500 + 3.5bar 5.0bar atwhich point relief valve cuts in.

So I suspect a dodgy earth on the gauge. Cheers for the confirmation of method.

Roger.

[eliot]

I nuked by Rover v8 by relying on an electric oil pressure guage, it said 15-20psi - it was actually 5 psi.
Eliot.

[gdr]

I took the precaution of fitting a 20psi oil pressure switch and very bright LED idiot light in addition to gauge.