Oil pressure warnings recurring - where next?

[scottyh56]

Over the last 15 months my 1988 T25 Westfalia 1.6td has been giving off oil pressure warnings, both the light and buzzer. These were occasional at first but on a trip half way down France and back in the summer became so regular that I made a B-line back to the channel ports.

On my return I bought a pressure testing kit and satisfied myself that pressure was OK, not great but at the easily accessible top sensor I had 1.5 bar at 2000rpm when hot. After the testing I changed that top sensor, changed the oil (to 15w-40 mineral) and filter (to Mann).

For 500 miles and over 2 months all seemed well. But now the buzzer is heard very occasionally and the warning light is there whenever hot and idling. These warnings have come in very quickly - over about 100 miles - rather more suddenly than the extended period over which they came on the 1000 mile French round trip.

Other symptoms:

White smoke for the first 5 miles - a condition that has been in place for 18 months or so
More seriously probably - has eaten a litre of oil in the last 600 miles. But no black smoke or external leaks evident.
Power seems OK and there are no nasty noises, to my ear anyway.

Any thoughts are appreciated. In particular do these symptoms indicate problems with the oil pump, oil pressure relief valve, clogged filter etc? Or is it now most likely a serious engine issue?

In the end I think I need to take it to a good experienced diesel mechanic for some serious diagnosis. Any suggestions within 50 miles of Brighton? I've had mixed experiences with those I have used in Brighton and what I hope I can get are firm recommendations earned from repeated good experiences.

Thanks

Scott

[lodgey62]

Could be the head gasket, look inside the water expansion bottle for a foamy brownish substance. Oil can pass into the cooling system when the head gasket breaks down and mixes with the water forming a foamy brownish substance.
Though I'm only a joiner!

[marlinowner]

I would say you have worn main and/or big end bearings to give low oil pressure and worn piston rings to cause excess oil consumption. Probably will only know for sure by dismantling the engine though. Or wait for it to go bang and then fit a 1.9t diesel or a GTI petrol engine.

[Enzo79]

I have had Oil pressure gauges on most things I have had, and I would expect to see the following:

Start up from cold and idling, would expect to see a few bar somewhere between 2 and 4 Bar depending on oil grade, and should slowly fall as oil warms up and gets thinner.

Once hot and idling I would still want to see at least 0.5 Bar, preferably nearer 1 Bar. If the low pressure switch on the Diesel T25 is like on the Mk1 Mk2 Golfs its a Blue one which is supposed to switch at 0.25 Bar, so if your light is on at idle then doesn't sound like you are even making that.

With some descent RPM on, like 3500Rpm I would want to see 2.5 Bar. The high pressure switch on the engine is most likely to be a 1.8 Bar one, and if you don't make that pressure above 2500Rpm that's when it brings the buzzer on.

If your not seeing that, then I would agree with the worn big ends and mains verdict above.

How many miles has it got on it? As that could make a big difference to the verdict.

You could always pop something even thicker in to see if it brings the pressure up, like some 20w50, I don't mean to run it on it permanently! But if the thicker oil brings the oil pressures back up to something acceptable, then I would say its definitely worn bearings letting all that oil pressure escape.

[dave friday]

One possibility is worn turbo bearings,the oil pressure reading on our van got to 1.5bar@2000rpm before I replaced the turbo!
Hi Enso,the high pressure switch is .9bar...

[Ian Hulley]

Sorry I can't help on specific diesel issues BUT I would like to say that original oil pressure switches aren't half as unreliable as we'd like them to be. The wiring to and from them however in my certain experience is very prone to cracking, decaying leading to resistance and false readings.

Have you replaced the cables from the multiplug that's near the black box in the corner of a WBX engine bay ? That worked for my 2.1 buzzer issues ...

Ian

[scottyh56]

Sorry I have not come back on this - I ticked for notifications and have received none...

Thanks for all the replies.

Ian - I've replaced the one switch and because I've been getting warnings from both sources and they have followed a pattern relative to time after oil changes I am inclined to believe that the pressure readings are real.

Dave - I've not read about turbo bearings elsewhere but shall have to add that to the list of possibles.

Enzo79 - This was a new reconditioned engine when I bought the van about 20,000 miles and 5 years ago. The fresh 15w40 made me think for 500 miles that all was well. I could do a fresh change and probably will because I want to get away - I suspect that I'd be OK again for a bit. But would that prove it's the engine against other possible issues such as filter clogging?

marlinowner - Short, not sweet but I do think you are representing how this will turn out. The 'new' engine in the van was probably not much cop to start with and I notice you are not suggesting that I fit another 1.6td. Is there a reliability issue with this engine so fundamental that one would risk putting in something different? The alternatives you suggest seem radical - can you point to places where I can read up on these options? The rest of the van is pretty good so if there would be serious expense I would reluctantly swallow if I could be confident of getting an engine which would still be OK 60,000 miles from now...

lodgey62 - Thanks but expansion bottle looks fine.

There was this bit at the end of my original post - "In the end I think I need to take it to a good experienced diesel mechanic for some serious diagnosis. Any suggestions within 50 miles of Brighton? I've had mixed experiences with those I have used in Brighton and what I hope I can get are firm recommendations earned from repeated good experiences. " Nobody's put me off that idea, hopefully somebody will come along who has a suggestion.

Cheers

Scott

[marlinowner]

I suggested the possibility of going to a 1.9TD or a GTI petrol engine not because there is a particular problem with the 1.6T engine but because it is reasonably easy to change to a more modern VW engine and they are readily available in good second hand condition. It may well be a cheaper option than getting your engine rebuilt or replaced with a reconditioned one. There is a fair amount of info on this in the wiki.

[dbz864]

You say you have checked the pressure with a gauge and its " OK" (which is the important thing)?, you say the light comes on when hot at tickover only ? Low pressure on tickover is not a massive concern, not great but not worth binning the engine for. increase the tickover a bit, put a good 20/50 oil in, may be enough to knock the light off, just use it and chill out.
you could have a recon engine fitted and have the same problem within 5k miles. Smoke on start up, is probably just a glow plug down. Does it run lumpy on start up from cold?

[scottyh56]

More apologies for a tardy response here! With Christmas arriving I think I'd rather forget about the camper woes!!!

marlinowner - Your logic is spot on and I will go look. Of course I have to find somebody who knows what they are doing, especially with unconventional mods.

dbz864 - Making sense - it does not run lumpily, is a brilliant starter but hot idle RPM is only about 700. Red light goes out at 800 - 850 rpm. I have tried various searches to know how to increase the idle revs but failed to find how to do this. Must be really simple but I'm missing it...

And I think I will change to 20w50 after Christmas. I have had recovery insurance all 5 years and never had to call out once - when it comes down to it engine death seems to be the cheapest and most certain way of diagnosing this issue, it just needs a certain philosophical state of mind!

[scottyh56]

I am now returning to this if I may with a little more evidence on symptoms.

To recap briefly, oil pressure warnings, buzzer mainly, then red light, had been becoming GRADUALLY worse over a period of 1000 miles. So I changed the oil (15W40) and filter 500 miles ago well ahead of usual schedule. This 'cured' the annoyances but then, after 500 miles they VERY QUICKLY returned, albeit now the red light was incessant at idle, buzzer only very occasional.

I changed the oil to 20W50 but did not change the oil filter. I was expecting an improvement, but got really got none. Red light at idle after 3 miles!

So today I changed the filter only. This has got rid of all the warnings.

So I assume that the filter is becoming clogged as the oil carries crap through it. How long before the warning returns I wonder?

I am tempted to drive now until the light returns and simply change the filter again as necessary. If the gap between changes increases then the crap is being filtered out and we are happy. If the gap reduces then crap is being generated faster than it is being filtered and that probably means the engine is being worn away...

Is my logic OK?

Thanks

[123-jn]

some cheaper oil filters have dodgy bypass valves that allow oil to bypass the filter altogether , depending on the engine this can cause pressure issues. I'm not sure how the bypass flows on one of these engines. Fram filters at one point were famous for it.

[tyneside-t25]

Hi Scotty.
Try flushing the engine out with flushing oil,just incase there's gunge floating around the engine & clogging the filter / oil galleries etc up.. could be a tenner well spent

[scottyh56]

Sorry - still not getting notifications of replies!

Thanks for the messages...

I use Mann filters which I think are meant to be good so should be OK on that front.

Flushing is an interesting suggestion - I shall however first wait to see how things develop following the filter change. I've still only done 20 miles!