jwillman

Took my 79 to Cars and Coffee in Leander, TX today. On the way home stopped to feed my 13 year old, 6 ft and 185 lbs, requires regular feeding.

In the drive thru I started to notice significant valve noise. Once I got to speed and back to the house about 2 minutes away the valve noise was gone.

Outside air temp was high 80's. I did an oil change when I first got her and it has been driven sparingly has I worked through all the other deffered maintence. I am running Mobile 1 . Oil pressure was showing 4 BAR in 5th gear at 65 MPH at operating temp. Slighty above 1 bar at idle.

Engine has at least 165K, odo was inop when i got it, and I have no maintenance history for the period before I bought the car.

Is this typical, indicative of an oil pump issue, blocked oil passages or something more ominous?

GlenL

Old car with hot oil running thin. What weight is in there?

pcar928fan

At idle and fully warmed up oil pressure should be around 2bar...I have seen just below that on really hot days when the car is fully HOT and a little above it just after full warm up.

My '81 tends to run low OP, but I never worry about it...I just keep on keeping on with it. Have not noticed the valve noise, but I am half deaf (or more) and am not sure I would know that is what I was hearing anyway...

Keep us posted Jim... Oh, there is a new owner and his son over on 928OC forum working on a project car almost exactly like yours, I'd love it if you would touch base over there with them and see what questions they might have for you...

jwillman

Mobile 1 - 15W 50.

PHIL928

should be 3 bar at hot idle, you need to change to a thicker oil for your climate.
20W50 is always the winner

jwillman

I had done a search to see if someone had published some typical / minimum oil pressure BARs based on RPM and environmental conditions.

Anyone else in texas moved to a heavier oil? Any implications during our cooler seasons?

jwillman

Update!

I ran the car for a bit tonight in the driveway. Once warmed up the oil pressure at idle was 2 bar and within seconds of reaching idle I began to hear what I assume is valve noise. Once I accelerate to around 2500 RPM I hit 5 bar. On deceleration there is no valve ticking until idle and at 2 bar it begins within 5 seconds or so.

All suggestions welcome - okay short of parting her out!

GlenL

Get some 20W50 from Amsoil, Royal Purple or other "boutique" oil and give it a try.

It's really pricey but I've found much better oil pressure at the track with the Amsoil 20w50 Racing oil than with Mobil1.

Exact oil pressure is questionable with variations in sensors and gauges. Since yours clatters with low oil pressure I think the issue is identified. You could try a new oil pump. Not too hard to install.

GregBBRD

Your oil pressure seems quite normal, to me.

If it is a sticky lifter, pour in a bottle of Swebco 502. That should fix the sticky lifter, very quickly.

I doubt you are going to "see" much difference between 15/50 and 20/50....although I run 20/50, in these engines, almost exclusively. Certainly not enough to make it worth the money to change it, before it is due to be changed. Keep in mind that the "15" number is a "cold" number and the "50" numbers are for "hot oil"....and they are the same.

"Blocked oil passages, oil pump problems" are virtually non existant, in these engines.

Try the Swebco. It normally will "fix" a noisy lifter in minutes, if that is really the noise.

GlenL

The "hot" number is evaluated at 100C which is not that hot for oil in an engine.

I've run 20w50 Castrol, 15w50 Mobil1 and 20w50 Amsoil TRO. Moving in that order, they engine showed better idle oil pressure when hot to very hot.

GregBBRD

I personally consider 100C to be the "perfect" oil temperature and try very hard to get/keep my engines to that temperature.

I agree that your results would be similar to the results that Kibort reports with the Amsoil. Almost makes one think that they are "cheating" a little bit when they "rate" their oil.....thicker oil is the only way that one can have more pressure, at the same temperatures.....it's pure hydraulics 101.

Might be more accurate to call it 20w60?

jwillman

Anyone know of a local source for Swebco 502?

GregBBRD

I certainly stock it, if you can't find it closer to you.

Call Mary and she can eaily ship you a bottle, if you can't find it.

jwillman

I am still evaulating my low oil pressure at idle. Ran the car this morning and after it was good and warm, outside air temp at 11 AM a cool 91 deg, oil pressure is down to 1 bar at idle. Cruising I get 4 bar in 4th at 3000 RPM and if I shift to 5th at about 2200 RPM I am at 3 bar.

That seems low. Oil, oil pump ?

GlenL

That is low.

What oil are you running now?

There are a few components to try replacing.

The first check I'd make is to verify that the oil pressure is low and you're not suffering an electrical or sensor issue.