oil pressure concern

[jettaman8691]

The car is a 1990 Jetta with a 1.6l td, 5 spd. Power is real good, burns very modest oil (though it does leak, as all us old things do from time to time). Oil pump is brand spanking new.
As the idiot light for the oil pressure has been coming on with increasing regularity, I installed an actual gauge to see what is going on. At start up the pressure goes up to 75#, as expected, and drops down as things warm up. At full driving temp the oil pressure is at 15#. At idle it looks to be at around 5#.
Should I be concerned? The car drives great, does not knock (other than the normal diesel clatter), and does not smoke.

[bscutt]

15 at speed is really low in my experience but I have never had a gauge on my VWs. 5 at idle seems extremely low and would surely trigger a light. IN the old days I would say main bearings but that's on old american V8s so hard to say. I'm sure someone else on here has more experience with specific minimum pressures for these engines and possible causes of low pressure.

[vwtyp133]

When all else is right, the main bearings in these diesels often have a crazy long life.

IMO a more likely suspect is the rear bearing on the intermediate shaft. Some people put so much tension on the timing belt that it yanks the IM shaft sideways enough to wear out its rear bearing, thus bleeding off lots of oil pressure. Top end seems to suffer the most from the lack of oil, but when follower buckets get stuck, valves get stuck & can potentially involve lower end assembly too.

If that's the problem, shut it off & fix it now; new IM shaft bearings need to be installed. Good luck.

[sgnimj96]

Oil pump is brand spanking new.

Is low oil pressure why you got a new oil pump?

I've read about a seal 068 145 117 B (dealer item) that goes at the bottom of the vacuum pump that can affect oil pressure some, relief valve in the oil pump being stuck open from debris can affect it alot, oil pickup clogged lol. Those are relatively easy checks. New IM shaft bearings is a serious job.
Seems like a new oil pump would have made the oil pressure better than before no matter what the reason for the low pressure.
My oil pressure (cheap sunpro gauge) is over 100 cold, 18 hot/idle

[jettaman8691]

Well, if the intermediate shaft bearings are indeed the problem, and it looks likely to be so, then that is most likely the end of this motor. Those bearings are pretty scarce. Does not look like Jack even has them. Dang. Just when I was trying to sell this thing. Karma?

[sgnimj96]

?
http://vwdiesel.net/forum/index.php/topic,1676.0.html

I searched the clevite# and found it (competitor's name removed by moderator)
(another competitor's name removed by moderator)sells em already reemed
I'd sure want to be really sure before jumping into that project...

[jettaman8691]

Thank you for that. I pulled the vacuum pump and found a bit of back/forth movement on the shaft, and just a tiny bit of movement side to side. It is most likely a problem.
I have an older model of mechanical head 1.6L motor that I could probably rob if I need to. These motors are pretty interchangeable over a wide year range.

[TylerDurden]

IM shaft bearings are not that difficult, and the front one is usually the culprit due to overtightening of the timing belt.

Lotta info online on howto... I'd change 'em and enjoy life.

[jettaman8691]

Thanks for the advice.

[jettaman8691]

Well, found a hole had developed in the oil return line from the turbo to the oil pan. Fixed that and the oil pressure seems to hold quite well. The oil drip from the hole has been increasing over the past few weeks, and coincides with the pressure loss. The hole was hidden behind part of the clamp, evidently vibrating against the pipe.

[Fatmobile]

Oil return line shouldn't cause a loss in oil pressure,.. unless you lost enough oil.

[jettaman8691]

I would not have thought so either, but drove it quite a bit after the repair and was very happy with the stability of the pressure. Sold the car now to folks who have a great deal of experience with VW diesels, so happy to see it has a good home.

All out of the VW vehicles now and so will leave this forum. It has been great, especially having read Hagar when he came on and sadly died and went to Scandanavian heaven. Cheers, and thanks for all the fish.

[Fatmobile]

You'll be back, ha.