Oil pressure problem...help please

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Tomc1958
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Re: Oil pressure problem...help please

Post by Tomc1958 »

Hi all sorry for the delay in updating. I've been experimenting with the van. When I let the engine warm up at idle for about 15 minutes and then drive there is no problem at all with the oil pressure dropping to zero and then picking back up. I've done this twice now and it's been fine. When I've driven the van more or less from cold (allowing a minute or two for oil to circulate) the pressure still drops to zero at about 2 miles and comes back up approx 8-10 seconds later. The warning light comes on at the same time. This always happens at the same distance from home and is not an intermittent fault...it's as if something is opening up internally and closing again 10 seconds later

This morning I ran at idle for 22 minutes and noted pressure from the dash gauge at 1 minute intervals...as follows. The gauge was fitted last year. 10/40 oil in whilst I run the engine in....is 20/50 best after this?

Minute Pressure/Bar
1 2.5
2 3.0
3 3.0
4 3.1
5,6,7,8,9,10 3.2
11,12 3.1
13 3.0
14 2.8
15 2.6
16 2.4
17 2.2
18 2.2
19 2.1
20 2.0
21 1.9
22 1.9

I've spoken with two VW specialist engineers, one says its the oil pump has a "bleed off" problem because the pump isn't manufactured to the exact specification for the engine. The pump is "under size by 4 thou to the case bore + the oil pick up galley holes are the wrong size." The other company says it sounds like the pressure relief valve.

I'm guessing here but could it be the pressure drops to zero whilst the oil cooler is filling up and then pressure returns to normal once it is full? I know nothing about mechanics nor how the pressure system works but when left to idle and no stress put on the engine, warming up happens more slowly hence the pressure drop doesn't occur? When driven from cold the engine is under more strain and it takes more time to sort itself out once the oil is hot? Hope I'm making sense?? Could someone point me in the direction where I can read about how the pressure system works. Is the valve pushed up by the spring when engine cold and then down once hot (internal pressure of the heat) thus forcing oil into the cooler??

For the time being I'm only driving it AFTER I've left it at idle for 15 minutes.... I did that this morning and drove around for 40 miles with no problems. Once I'm driving everything is fine, the engine is like new and it's a real pleasure to drive, much smoother and less noisy the pre re-build.

Thanks folks for all your help and advice. Pic attached of pressure gauge location

Tomc1958
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Re: Oil pressure problem...help please

Post by Tomc1958 »

Need to reduce file size of the pic to upload :-(

Tomc1958
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Re: Oil pressure problem...help please

Post by Tomc1958 »

privatevarmobileContainersDataApplication99987406-62D5-4948-B80E-86F093E41708tmp75F34737-7404-4D10-B2D1-54A46F758211Image.jpeg
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937carrera
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Re: Oil pressure problem...help please

Post by 937carrera »

Hmm, very strange.

On the oil pressure readings it's most strange that the pressure starts off at only 2.5 bar and then increases, though I am making the assumption that the engine speed is constant. ??? I would have expected something like 4-5 bar possibly limited by the PRV, dropping away as it heats up

After 21 minutes of running the engine will be up to temperature and you are still seeing 1.9 bar, which for idle speed is actually very good. The warning light operates at ~ 0.25 bar

How does the first company know the pump is undersize to the bore and the gallery holes are the wrong size. Have they had the engine and removed the pump ?

There is something weird about the oil pressure being lost when the van is driven without warming up. The prv actually allows excess oil pressure generated when the oil is cold to bleed away, rather than being forced into the oil galleries. There will also be a separate thermostat to the oil cooler to allow for more rapid warm up and the cooler is full at all times

From your description then it sounds like the PRV is allowing all the oil pressure to drain away in a certain set of conditions, or there is some mechanical blockage preventing oil getting to the gallery where the oil pressure switch is.

I am assuming that the feed for the oil pressure gauge comes from between the pushrod tubes under the engine, can you confirm this ?

Have you taken the engine back to the builder - it seems they are the ones that should be sorting it out.
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tobydog
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Re: Oil pressure problem...help please

Post by tobydog »

Tomc1958 wrote:Oil pressure drops to zero at about 2-2 1/2 miles from being driven from cold.

Do you pass any ley lines :shock:

Is the oil level correct?

I use 15w50 in the old girl :)

As 937 said, the builder should take some resposibilty for the problem.
Knowledge is power
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Tomc1958
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Re: Oil pressure problem...help please

Post by Tomc1958 »

tobydog wrote:
Tomc1958 wrote:Oil pressure drops to zero at about 2-2 1/2 miles from being driven from cold.

Do you pass any ley lines :shock:

Is the oil level correct?

I use 15w50 in the old girl :)

As 937 said, the builder should take some resposibilty for the problem.

Thanks, oil level is correct, checked every time I go out in it. Mechanic who did the rebuild is helping and as mystified as everyone else I've spoken with. I think its looking like oil pump (which is new) and/or oil pressure relief valve (also new). Been told today that with parts supplied these days not being original manufacture there may be very minor variations in tolerances. Problem existed before the rebuild and anything obvious that might cause the problem has been replaced. Must be something to do with running temperature/oil viscosity for it to happen at the same distance from cold start on flat roads??

Tomc1958
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Re: Oil pressure problem...help please

Post by Tomc1958 »

937carrera wrote:Hmm, very strange.

On the oil pressure readings it's most strange that the pressure starts off at only 2.5 bar and then increases, though I am making the assumption that the engine speed is constant. ??? I would have expected something like 4-5 bar possibly limited by the PRV, dropping away as it heats up

After 21 minutes of running the engine will be up to temperature and you are still seeing 1.9 bar, which for idle speed is actually very good. The warning light operates at ~ 0.25 bar

How does the first company know the pump is undersize to the bore and the gallery holes are the wrong size. Have they had the engine and removed the pump ?

There is something weird about the oil pressure being lost when the van is driven without warming up. The prv actually allows excess oil pressure generated when the oil is cold to bleed away, rather than being forced into the oil galleries. There will also be a separate thermostat to the oil cooler to allow for more rapid warm up and the cooler is full at all times

From your description then it sounds like the PRV is allowing all the oil pressure to drain away in a certain set of conditions, or there is some mechanical blockage preventing oil getting to the gallery where the oil pressure switch is.

I am assuming that the feed for the oil pressure gauge comes from between the pushrod tubes under the engine, can you confirm this ?

Have you taken the engine back to the builder - it seems they are the ones that should be sorting it out.


I'll give it another go in the morning with initial start up pressures. The engineering company asked me which oil pump had been fitted so I told them the model numbers etc and that is what they came back with. I'll find out exactly where the feed for the pressure gauge comes from.... I thought it is from the top of the engine where the pressure switch is located? Engine builder is helping all he can and speaking with people. The guy who said the oil pump wasn't quite right said they make their own oil pumps for the vehicles they work on. Also the guy who said it sounds like the pressure relief valve sounds like the cause was someone a major VW parts supplier deals with. I've checked both out on the internet and they look like very specialist and knowledgable set ups. You mentioned a thermostat to the cooler.....could it be a faulty thermostat causing this?? Thanks for all the help, it is hugely appreciated

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937carrera
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Re: Oil pressure problem...help please

Post by 937carrera »

I just had an idea, and then realised I had mentioned it before.

Change the oil filter. Go for a decent make,and make sure it is the correct one

Mann W920/17 should be OK

Oil filters also have a bypass valve in them, sometimes these can be troublesome. Cheap to do, see what the engine builder thinks about trying that.
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
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tobydog
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Re: Oil pressure problem...help please

Post by tobydog »

Anti return valve also
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mrhutch
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Re: Oil pressure problem...help please

Post by mrhutch »

937carrera wrote:I just had an idea, and then realised I had mentioned it before.

Change the oil filter. Go for a decent make,and make sure it is the correct one

Mann W920/17 should be OK

Oil filters also have a bypass valve in them, sometimes these can be troublesome. Cheap to do, see what the engine builder thinks about trying that.

First response from me on this thread:
mrhutch wrote:have you got the right oil filter fitted?

THIS WILL BE THE ISSUE
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bigbadbob76
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Re: Oil pressure problem...help please

Post by bigbadbob76 »

Sounds like a sticky PRV to me.
At start-up the pressure is high enough to open the PRV, if it then sticks open the pressure will drop as the oil warms up, then at a certain temperature the case has expanded enough to free the stuck PRV and the pressure come back up.
If you warm it up at idle the pressure might not be getting high enough to open the PRV so it doesn't stick.
Replacing the PRV won't neccesarily stop it sticking if there's a burr in the bore it sits in.
Just my 2p worth but sounds feasible.

I doubt if it's the oil filter bypass as whether it opens or not the pressure shouldn't drop unless the filter is blocked and the bypass is stuck shut, then the pressure after the filter would be lower than the pressure from the pump. but it's a new filter so shouldn't be blocked, and it did the same before the rebuild.

Best of luck with it, fingers crossed for you Tom.
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Tomc1958
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Re: Oil pressure problem...help please

Post by Tomc1958 »

Thanks for that....just texted the builder and he said thats the filter he's got to put on on Monday when I see him for oil change now I've run it in. :ok :ok . I must have missed that post. Been out for a drive in it again this morning after warming up and checked oil level before I set off. Unless I made a huge mistake in checking oil levels which I don't think I have I needed to top it up....the level had dropped to the lower mark on the dipstick and its consistently been on the higher mark since I got it back from the rebuild. No pool of oil outside my house and it certainly hasn't been smoking as I've been driving. I keep a drip tray under it when I'm at home. Maybe I did make a mistake about oil level yesterday because I think pressure readings today might be higher. Anyway, topped it up and checked levels now its cool and its sat nicely at the top marker on the dipstick, dipstick is fully inserted.

Minute Bar
1 3.5
2,3 3.1
4 . 3.2
5 . 3.3
6 . 3.4
7-11 3.5
12-14 3.4
15 . 3.2
16 . 3.1
17 . 2.9
18 . 2.7
19 . 2.5
20 . 2.3
21 . 2.2
22 . 2.1
23-25 1.9
26 . 1.6
27 . 1.5
28 . 1.5
29 . 1.5

After I got back from about a 25 mile drive it was ticking over at 1.1 45 mph and it was 2.1 I've not taken it much over 45mph as yet.

Just remembered this morning something which may have a bearing but I'm not sure. When I got the van just over 2 years ago I had it converted to also run on LPG, Steve Shaw (RIP) did the conversion. When the engine was rebuilt I was told the valve seats were fine and were hardened ones already in there. Since getting it back from rebuild I've only run it on petrol anyway. Mech who did the rebuild is being very helpful but Im finding out as much info as I can. As said going back on Monday for oil and filter change and another look at the PRV......and also to see if there's any sign where its losing oil from :-( The dipstick tube is in the right position and bolted on and dipstick pushed fully home so I'm pretty convinced it isn't a misread. Ho hum. Thanks again folks

Tomc1958
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Re: Oil pressure problem...help please

Post by Tomc1958 »

bigbadbob76 wrote:Sounds like a sticky PRV to me.
At start-up the pressure is high enough to open the PRV, if it then sticks open the pressure will drop as the oil warms up, then at a certain temperature the case has expanded enough to free the stuck PRV and the pressure come back up.
If you warm it up at idle the pressure might not be getting high enough to open the PRV so it doesn't stick.
Replacing the PRV won't neccesarily stop it sticking if there's a burr in the bore it sits in.
Just my 2p worth but sounds feasible.

I doubt if it's the oil filter bypass as whether it opens or not the pressure shouldn't drop unless the filter is blocked and the bypass is stuck shut, then the pressure after the filter would be lower than the pressure from the pump. but it's a new filter so shouldn't be blocked, and it did the same before the rebuild.

Best of luck with it, fingers crossed for you Tom.


Thanks Bob, I'm learning on my toes here and a few have now mentioned the PRV so it will be looked at again on Monday when it goes for oil change...... I think a good fiddle around in the PRV bit is in order. I'll be over the moon if it is that because it should be straight forward fix although having said that I'm not sure where I've lost oil from.....I'm hoping Ive just misread the dipstick but don't think I have

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Swebby
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Re: Oil pressure problem...help please

Post by Swebby »

Maybe the oil filter went on empty and hadn't been filling properly till that last trip? Not really my area of expertise this but might account for a drop.

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Tomc1958
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Re: Oil pressure problem...help please

Post by Tomc1958 »

Swebby wrote:Maybe the oil filter went on empty and hadn't been filling properly till that last trip? Not really my area of expertise this but might account for a drop.

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Thanks Swebby, sounds feasible but I'm no expert.....where's that postage stamp and I'll write down all my knowledge :-) Although the amount of oil I put in was possibly the same a filter might contain? Would explain why I dont' have a puddle of the stuff outside the house...and with the road wet it would be pretty obvious. It's a good thought

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