I've been meaning to post my observations of oil pressure and water temperature readings, from my recently re installed guages, after oil change, but never got round to it. Today, however, there has been a change.....

initially, cruising through the night at 40mph, temperature barely got over 60 whilst oil pressure hovered over 30 psi.
I was generally pleased, suspected the thermostat not opening but didnt have time to investigate further.
Today, having passed MoT, hurrah, and driven 90 miles in much warmer weather, however, temperature was up to 75 and oil pressure slowly dropped to 20. I thought that was a result of the higher running temperature, but checked, just in case.
Evidence of water in oil. Not a lot, emulsification on inside of filler cap, now a blob of gunge on tip of dipstick. No unusual sounds or smells. Evidence of rusty water around thermostat housing, filler tube area.

optimistically, im hoping expansion of water squirted into partly open dipstick tube, but I doubt it.

can I trust the guages? what reading s do others have? Am I looking at head gasket change? What else might it be?

Currently in London on way to Glastonbury bus rally. Any advice welcome....

My bus number (if any): 1842

It could be just condensation inside the engine, but the description sounds very much like head gaskets weeping.

What's the exhaust like?

Could be a cracked head, dropped liner, injector seats leaking...unlikely to be condensation.

I had a problem on my Range Rover recently with head gasket weeping, not overheating, just pressurising the header tank. Cost £1800+ to change the head gasket, lap the valve (it's done nearly 240000 miles). But the local garage suggested a liquid steel stuff, pour 2 cans in the water system and that cured the problem! It may well work on a bigger engine. It's about £20 a can and I needed 2 cans for the 3 litre engine, so I'd suggest a 9.6 would need 6 can, it's worth a try. Steel Seal I think it's called.

Oil pressure will go down a the engine gets hotter, my GS runs at 70psi when cold, and down to about 40 psi when hot.

My bus number (if any): RML2532

Hi Ian
I have both an oil and temperature gauge fitted in my Regent V (this is part of the standard spec for the Regent V so it hasn't been retro-fitted). The Regent also has an AV590 engine so there's a direct comparison with your vehicle.

Oil pressure generally is around 40 psi cruising at around 35-40mph which I've been told is about right for an AV590, so I think 20-30psi is probably on the low side. Temperature generally hovers between 75 and 80 Centigrade and rises to around 90-95 on a long uphill climb.

Hope that helps.

Steven

My bus number (if any): RM 1699 Eastbourne Regent III (AHC442) Regent V (KHC369)

I forgot to add, the cylinder head gasket had to be changed on the Regent V some while ago. This was caused by the failure of the thermostat to open and while the water in the radiator was relatively cool, I remember that the temperature gauge shot up to about 120! I don't recall any water in the oil but there was copious amounts of white smoke which is a sure tell tale sign that the gasket needed replacing.

My bus number (if any): RM 1699 Eastbourne Regent III (AHC442) Regent V (KHC369)

The AEC specs for engine oil pressure do vary between the different engines, however they all relate to minimum pressure at maximum revs. Two readings would worry me. First below 10 psi at idle and second any fluctuation of pressure at a constantly-maintained hot revs which are significantly above idle speed. A rapidly vibrating gauge needle can usually be overlooked.

There is no mention of what grade of engine oil is being used, nor of whether the engine has an oil filter or not. This has a relevance to your findings.

Condensation in the oil filler or dipstick tube is nothing necessarily to worry about. Since the engine has presumably stood for some time (years) in a shed before being fitted a small amount of contamination of fresh sump oil would not be surprising. However all these concerns may have nasty causes, a close eye on oil and coolant consumption plus monitoring the gauges is going to be needed.

That's all useful information, thanks gents.

it's a 690 ex generator set engine, has a modern spin on oil filter, not totally sure what grade oil as someone else changed it.

Took 2 litres of water this morning, some of which has left its rusty deposit on both sides of engine. About t check hose clips etc.

Temperature sensor is rear of head
Top of rad hot bottom cold

guages were showin 20plus at tick over and 20 when warmed up to 75 degrees just now.

I am very keen not to seize up on way to Finsbury park,, as I did 10 years ago

My bus number (if any): 1842

Oh, and the exhaust is clear.

My bus number (if any): 1842

If anything, I'd say my thermostat is stuck open

My bus number (if any): 1842

Injector seats leaking? Tell me more.
Since I've given the engine area a deep clean im able to spot new stains.

Today i noticed no.5 injector appears damp around base and its not the dribble return pipe

My bus number (if any): 1842

Ian,

Martin Detheridge is at Usk just across the Severn bridge, so not too far from Glastonbury, if you contact him (London Bus 4 Hire) he may well be able to help by giving a professional opinion at the vehicle.

The 760 engines run at about 70 psi oil pressure when cold; when hot it drops down to about 40psi when the pressure relief valve opens. I've rebuilt several of those over the years for Reliance coaches.

My bus number (if any): RML2532

My bus number (if any): 1842

Hi Ian
Not sure who my colleague was.

There could be a number of things that can cause the problems your having,
your more than welcome to call me on 07530 904650 and hopefully I can help.

Regards
Martin
London Bus 4 Hire & Red Routemaster.Com

My bus number (if any): London Bus 4 Hire Red Routemaster Fleet