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Effect on Oil Pressure Due to Head Issues
by
thomas m
on 03 Sep, 2017 14:39
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In this diesel engine how much does wear on head components contribute to reduced oil pressure compared to
the intermediate shaft, rod/crank bearings, intermed shaft, vacuum pump seal, etc. ??
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#1
by
vanbcguy
on 04 Sep, 2017 14:41
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It certainly can have an impact... Do you have a specific problem you're trying to troubleshoot?
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#2
by
thomas m
on 04 Sep, 2017 18:47
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Before a major rebuild, if that becomes necessary, I might try replacing components that could boost my oil pressure a bit. I'm curious as to how much difference each change might make. I've replaced the oil pump and the vacuum pump "green" seal without much rise in pressure. I've been thinking about doing the rod bearing and main bearings next. I don't want to remove the engine just yet. It start and runs ok with nominal oil consumption.
If new bottom end bearings would improve the oil pressure, I would suspect that the intermediate shaft is not a major contributor.
The oil has been changed every 3000 mile for the life of the car and I didn't find and dirt or metal in the oil pan.
I wouldn't mind taking it in to a reliable shop, but I don't have one in mind at this time.
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#3
by
air-cooled or diesel
on 04 Sep, 2017 20:39
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what kind of oil pressure readings are we talking about?
what oil are you using? grade & brand?
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#4
by
thomas m
on 07 Sep, 2017 17:06
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I have a VDO electric gauge installed. I see an idle pressure of about 75 psi on start up and about 7-9 psi once up to high temp. The block temp on an 80-90F(27-32C) degree day is about 210 degrees F(99C). Pressure at cruise, 55-60 mph, is about 40 psi. I read block temp as estimated oil temp. I have a temperature pickup screwed into a threaded boss on the front of the engine near the oil cooler.
Occasionally, after it's really hot, I will get a red light at idle which is set at about 850 rpm. But it does not stay on. Specs on the VDO sender give a red light at a little higher pressure as compared to the original VW idiot light sender. I replaced the VDO unit with the original VW sender and I did not get the red light. I'm trying to be optimistic so I don't have to deal with a disaster......yet.
With the block temp stabilized at about 200F(93C), the light comes on at low idle and the 2000 rpm pressure is 25-28 psi. This is gauge pressure measured at estimated 2000 rpm/18 mph in second gear. Bentley says 28 psi @ 2000 rpm, operating temp at 140F(68C) with 10 W oil. I'm not sure how this relates to my numbers.
I'm using Delo 400 15W-40 Diesel Oil. I guess I could up the weight. I have a gallon of Delo 40W on the shelf.
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#5
by
ORCoaster
on 07 Sep, 2017 23:54
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What I read from all of what you scibed Thomas M is that you are right at the edge of the acceptable numbers. Your hot psi of 7-9 is low for idle, and the 2000 rpm numbers are on the edge as well. The one that gets me the most is your 40 psi at cruise. I am running old oil in my Rabbit right now and yesterday I was crossing from the coast to the valley where it was near 85 F. I had a solid 70 when warming up and the hot engine still held 50 at cruise. But then at idle I get 30 to 25 depending if really hot. Like your numbers, 100 C is hot to me.
So I would lean towards two things, the 40 W as you mentioned and checking the oil pump for any sort of grit in the relief valve. Just to be sure I was loosing some of the pressure being created by the pump in the first place.
Now might be a good time to jump up to the bigger vane pump.
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#6
by
thomas m
on 08 Sep, 2017 00:29
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I replaced the original pump last year with a new 36 mm unit. My sump was grit and debris free. But it's worth a check if I open it up.
I guess the next step will be the rod bearings and 40 W.
Maybe I'll change the oil first and see what that does. Then go for the rod bearings and the mains.
So I would lean towards two things, the 40 W as you mentioned and checking the oil pump for any sort of grit in the relief valve. Just to be sure I was loosing some of the pressure being created by the pump in the first place.
How do I check for grit in the relief valve?? I thought that it was crimped or can it be opened up???
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#7
by
air-cooled or diesel
on 08 Sep, 2017 05:58
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I see an idle pressure of about 75 psi on start up and about 7-9 psi once up to high temp.
I will get a red light at idle which is set at about 850 rpm.
that you are right at the edge of the acceptable numbers. Your hot psi of 7-9 is low for idle,
7-9 psi hot @head is right on as low as you (*can) should go, that is for a 5w-30 or even 5w-40 syn, for a 15w its even lower. so beware.
looks like its time to get into your lower end, like above, mains, rods, definitely main thing im shaft bearings, possibly im shaft its self. of course the inner im shaft bearing is a real problem to get to on way or the other, its no easy task to get a shop to do it. can you say disassemble engine, and tow car to shop and have them do it? either that or take bare block to shop,,. your gonna need to do more work, id say 1st check compression either that or you ll be doing more than rings. the head on the other hand is a good question, if your gonna keep it i suppose some visual under caps. other than that a visual of cam lobes, then you have chioces, you dont have a performance engine, rest of head may be ok. its up to you. perhaps disassemble and visual valve where they seat. lifters are one more question.
i had pointed out your vdo gauge? red light, i doubt it means much. the dash idiot/warning light means a lot here, other that that i dont know what that gauge light means, it may have a use, and certainly your running quite low. the way to do it, thread a 'T' or 'Y' into oil pressure hole and keep stock sensor, and also use an alternate sensor set up. you gotta be fancy here, i dont recommend you use any sealer compound on threads, id use a std copper washer, and you can now add sealer. prefer avaition permatex here. -that is sealer to copper washer and not
any threads.
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#8
by
ORCoaster
on 08 Sep, 2017 20:34
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You can get the spring out of the oil pump relief valve. Still have the old pump? Practice on that. You work the cap out and then clean it all up. When it comes to buttoning it up you drill a hole across the diameter of the cap and pump body and insert a cotter pin.
TheMan had a write up on it some place here. Poke around for Oil Pump relief valve or oil pump rebuild.
I did find this post that sort of describes it, and other items with graphic detail
http://vwdiesel.net/forum/index.php/topic,34730.msg332417.html#msg332417
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#9
by
diesel dub
on 02 Feb, 2018 01:38
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Would a stuck open oil squirter cause this low oil pressure problem at idle?
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#10
by
Dakotakid
on 06 Feb, 2018 14:36
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yes....no....I don't know...why do you ask?
How would you prove one is clogged without engine disassembly? my guess would be that they clog closed.
The most common source (in my mind) of low oil pressure on these is intermediate shaft bearing problems.
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#11
by
diesel dub
on 17 Feb, 2018 22:16
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I ask because i don't know either. Mine acts similar. Rebuilt engine. All new bearings and oil pump.