Rebuilt engine low oil pressure

Technical questions and answers concerning all models of VW diesel vehicles.

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Fatmobile
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Posts: 7564
Joined: Wed Oct 30, 2002 10:28 pm
Location: north central Iowa

Re: Rebuilt engine low oil pressure

Post by Fatmobile »

Weird that the same hose is used on the Mercedes.
It is a crazy looking hose that likes to rub on the alternator.

I love the early sciroccos but have never owned one.

I'm in Iowa and the only real change on titles is they now require a bill of sale when getting a car registered.
What state are you in?
'91 Golf gasser converted to a 12mm pump, M-TDI.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.
sgnimj96
Turbo Charger
Posts: 259
Joined: Thu Feb 20, 2014 2:08 pm

Re: Rebuilt engine low oil pressure

Post by sgnimj96 »

Central Florida on the East coast.
Cars rust from the top down quick.
I'm surprised that most people here still don't understand how rust works.
My efforts to thwart rust without doing a full paint job has ended up with ospho, cosmoline
or epoxy resin/putty. Doesn't look nice, but it holds the rust back.
If something isn't done, patina quickly turns into holes.

Got a friend with a cool older Suzuki sidekick that had some big cratering rust spots.
I went over there on my own one day and dug out the loose rust, sprayed some ospho,
told him he better fix it but at least it can dry out some during the day.
That was like two years ago.
Says he loves that car
but will drive it into the ground until it physically won't move. Then calls me :roll:

One great thing is there is no vehicle inspections here in FL (at least for now)
81' Scirocco 1.6D (conversion)
86 Golf 1.6D
85' 300TD
sgnimj96
Turbo Charger
Posts: 259
Joined: Thu Feb 20, 2014 2:08 pm

Re: Rebuilt engine low oil pressure

Post by sgnimj96 »

While waiting on the little vac pump seal,
I been searching for a 36mm oil pump and those things are practically NLA.
there's pretty much ONLY this https://www.partsplaceinc.com/vw-diesel ... 2/reviews/

I did find something on ebay but the part number I can't cross-reference anywhere
https://www.ebay.com/itm/393469335071?f ... BM7sDsh4dg
says it fits gas AND diesels ?
81' Scirocco 1.6D (conversion)
86 Golf 1.6D
85' 300TD
Fatmobile
Global Moderator
Posts: 7564
Joined: Wed Oct 30, 2002 10:28 pm
Location: north central Iowa

Re: Rebuilt engine low oil pressure

Post by Fatmobile »

I think the 36mm pumps were used on hydraulic blocks so they would be for diesel cars after '86.
Pretty sure the gasser oil pumps spin the other way
When I had low oil pressure problems the high flow oil pump didn't raise my oil pressure at all.
Ended up being the clevite I-shaft bearings and it was lower than yours.
So it's probably a different cause than yours,.. and I never thought to measure pressure at the head and oil filter.

Since your pressure is the same at the filter as the head I would think the pressure is getting dropped at the cam journals.
Maybe try to plastiguage them.
If they are a little loose it's easy to put some sand paper on a piece of glass to remove some of the flat surface on the caps.
that will lower them and make less space between the cam and caps.

I personally don't think your oil pressure is that low,
but could possibly be improved.
'91 Golf gasser converted to a 12mm pump, M-TDI.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.
sgnimj96
Turbo Charger
Posts: 259
Joined: Thu Feb 20, 2014 2:08 pm

Re: Rebuilt engine low oil pressure

Post by sgnimj96 »

Reading up on removing cam caps, might be a bad move for ME to start playing with those things.

Reading up on oil pressure vs oil flow also has me thinking I may be wrong about this being a real issue.

Now most of this is just hear-say, as I didn't even remove the head:
I bought this from a guy who supposedly spent a lot of money putting it together with the intent
of using it to make a lot of power, then lost time/interest to finish. It was actually bored .040 over - he said the engine builder
insisted on it as "the least he would bore a block" :roll:

Here was some of the ad:
freshly built, zero mile 1.6 turbo diesel for sale. True turbo block with piston oil squirters. Block,crank, and rods are from an 86 Quantum. Block was bored 1mm (.040"). New Mahle forged pistons. ARP main studs. 12mm head checked for cracks at machine shop. 3 angle valve job. New Tectonics Tuning titanium valve springs and HD valve seals. ARP head studs. Machining and assembly was done by a local, reputable machine shop. I have easily $2500 or more in parts, machining, and assembly.

The only bad sign was that my 11mm block's IM shaft inner journal
looked better (smoother) and increased the oil pressure a bit when I swapped it in.
I know it shouldn't need a 36mm oil pump but its (mechanically) easy to do. Found another one https://www.busdepot.com/028115105g
Just ordered a cheap boroscope for next time I have an IM shaft out. https://www.ebay.com/itm/403483467513?var=673472312393
I never got a good look at that inner IM shaft bearing(doh), but the outer looked good and overall rotation felt tight.
I used a stiff wire and the hole through the inner bearing felt like it does line up.
I'm going to try see If I can detect any up/down play in the inner IM shaft when I take the vac pump out again to do that seal.

Sorry for the long posts. I know most of this doesn't have clear answers. I just don't want to break anything.
81' Scirocco 1.6D (conversion)
86 Golf 1.6D
85' 300TD
sgnimj96
Turbo Charger
Posts: 259
Joined: Thu Feb 20, 2014 2:08 pm

Re: Rebuilt engine low oil pressure

Post by sgnimj96 »

Dang, just called busdepot and they DON'T have the 36mm oil pump. "Sorry..."
81' Scirocco 1.6D (conversion)
86 Golf 1.6D
85' 300TD
Fatmobile
Global Moderator
Posts: 7564
Joined: Wed Oct 30, 2002 10:28 pm
Location: north central Iowa

Re: Rebuilt engine low oil pressure

Post by Fatmobile »

Too bad,
they are a good reliable source for parts.
'91 Golf gasser converted to a 12mm pump, M-TDI.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.
sgnimj96
Turbo Charger
Posts: 259
Joined: Thu Feb 20, 2014 2:08 pm

Re: Rebuilt engine low oil pressure

Post by sgnimj96 »

The new rubber seal in the vac pump gear looked much better, tighter, but didn't change anything significantly.
I dropped the idle a bit and am surprised the oil pressure stayed the same.

My dynamic numbers are about the same as the OP in this 5-post thread
https://www.vwvortex.com/threads/1-6-di ... t-76845466
Does anyone know more about the mysterious "oil pump shaft bushings", specifically the upper one
just below the vac pump, affecting oil pressure?

I tried levering a large screwdriver against the end of the IM shaft, it feels solid. Not sure if that's a real test for play in the inner IM bearing.
81' Scirocco 1.6D (conversion)
86 Golf 1.6D
85' 300TD
colby
Site Administrator
Posts: 101
Joined: Wed Jan 29, 2014 9:46 am

Re: Rebuilt engine low oil pressure

Post by colby »

What kind of oil filter are you running on the engine?
sgnimj96
Turbo Charger
Posts: 259
Joined: Thu Feb 20, 2014 2:08 pm

Re: Rebuilt engine low oil pressure

Post by sgnimj96 »

Pentius "UltraFlow" PLB3569
I'm thinking it doesn't put up much resistance. Pretty large. Despite the fancy name, it's Made in China
My 1.6D filters get put on a little more than just hand tight, I use a filter wrench.
81' Scirocco 1.6D (conversion)
86 Golf 1.6D
85' 300TD
colby
Site Administrator
Posts: 101
Joined: Wed Jan 29, 2014 9:46 am

Re: Rebuilt engine low oil pressure

Post by colby »

I'm wondering if it might be worth trying a different one. I always ran the big Mann extra capacity ones, but I never checked oil pressure either. I know there can be large variances in oil filters and bypass pressure settings, filter material, etc. It'd be a cheap test anyways. I think Bosch makes a fairly decent filter too. I had a dealer with Mann filters in stock when I used to drive these cars, so it was easy to get them.
sgnimj96
Turbo Charger
Posts: 259
Joined: Thu Feb 20, 2014 2:08 pm

Re: Rebuilt engine low oil pressure

Post by sgnimj96 »

I ran the same filter in the previous engine and it had no oil pressure reduction.
81' Scirocco 1.6D (conversion)
86 Golf 1.6D
85' 300TD
colby
Site Administrator
Posts: 101
Joined: Wed Jan 29, 2014 9:46 am

Re: Rebuilt engine low oil pressure

Post by colby »

It has to be something else then. Cam journals, or I-Shaft bearings. I figured it was worth checking on anyhow, as in my own experience, I have seen different oil filters do weird things with oil pressure. I'm not entirely certain I'd be totally worried in your situation, either though. I agree that oil pressure should be higher than what you're seeing on a rebuilt engine, but I'm also wondering if some "burn in time" is in order too, to get things seated. It seems like a lot of work was done. I guess worst case scenario, you're looking at replacing the i-shaft bearings or doing some work on the cam caps/surfaces.

I think you've eliminated all other possibilities, honestly. I don't think your engine will implode. I mentioned previously a mechanic friend of mine said the engine only needs 8 psi to hold the top end together, but I also agree that with a rebuild, it should be higher than what you are seeing.
sgnimj96
Turbo Charger
Posts: 259
Joined: Thu Feb 20, 2014 2:08 pm

Re: Rebuilt engine low oil pressure

Post by sgnimj96 »

I know this has too many possible factors going on, in addition to
me not knowing how the engine was really put together, IN ADDITION to me not being
willing to just start taking things apart to measure gaps.
Even just plastigaging the cam caps - after reading posts about people cracking
caps like it's an easy mistake- that calls for a new head. :shock:
Then the possibility of the builder leaving higher tolerances in the bearings as
some kind of racing spec is also there. The seller had some "big" plans for that
engine before time got in the way - big turbo, head springs, forged pistons, IP w/ no governor.

I'm going to take it on a longer highway run and see how acts after a couple hours
on a warm day. I may get the bigger oil pump, but it seems the only one to be
had is a knockoff "vaico" brand for $120 from partplace. The vw ones are out of my price range
for something that may prove to be irrelevant.

For the deal I got it still all seems worth it, and I'm learning more.
Plus I got a good vnt-15 turbo as a spare with it, and a few other things.
Btw, one of those things was a solid-spline clutch disk - yea, a 200mm
clutchnet disk with NO springs (I didn't install that thing, lol)
81' Scirocco 1.6D (conversion)
86 Golf 1.6D
85' 300TD
Fatmobile
Global Moderator
Posts: 7564
Joined: Wed Oct 30, 2002 10:28 pm
Location: north central Iowa

Re: Rebuilt engine low oil pressure

Post by Fatmobile »

Ohh you have a VNT-15 that came with it.
That's my favorite turbo for the 1.6.
'91 Golf gasser converted to a 12mm pump, M-TDI.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.
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