| Author |  Topic  |
FromTheKeyboard
Starting Member
USA
39 Posts |  Posted - 30 Jul 2017 : 21:56:58  
| Hello again.
So after spending about 6 months or so getting my V4 running again, I've noticed that the engine is only getting around 5-10 PSI of oil pressure at idle.
I have both the gearbox & engine full, and nothing below the cylinder heads was messed with.
I can't seem to find any specification for oil pressure in the owner or repair manual, and I really don't want to ruin this engine before it's been put back in the car.
TLDR: Is 5-10 PSI on the oil pressure OK for this engine? Am I doomed? |
Edited by - FromTheKeyboard on 30 Jul 2017 21:57:47 |
|
Joshinator99
Starting Member
USA
39 Posts | Posted - 31 Jul 2017 : 03:38:08
| Are you getting the low oil pressure light on? It kicks on between 4.3 to 8.5 psi according to the workshop manual. If not, the gauge may be bad. I would try to get a manual gauge tapped in for a second opinion.
What are you running for oil? Thinner weight and/or synthetic oil will show a lower oil pressure since it pumps easier. Not necessarily a bad thing, but your pressure should be high enough at idle to avoid the warning light.
1972 Sonett III |  |
|
FromTheKeyboard
Starting Member
USA
39 Posts | Posted - 31 Jul 2017 : 05:24:24
| quote:
Originally posted by Joshinator99
Are you getting the low oil pressure light on? It kicks on between 4.3 to 8.5 psi according to the workshop manual. If not, the gauge may be bad. I would try to get a manual gauge tapped in for a second opinion.
What are you running for oil? Thinner weight and/or synthetic oil will show a lower oil pressure since it pumps easier. Not necessarily a bad thing, but your pressure should be high enough at idle to avoid the warning light.
1972 Sonett III
I forgot to mention, I'm using an aftermarket set of gauges (but I believe they were intended for the 96), and I'm just looking at the numbers shown.
Additionally, I am using synthetic 10W/30 (manual specified) in the engine, with non-synthetic 80W/90 in the gearbox.
Is there some way of checking oil coverage without breaking a sealed gasket? |
Edited by - FromTheKeyboard on 31 Jul 2017 05:26:47 | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 31 Jul 2017 : 12:28:08
| Unless it's a completely rebuilt engine, I would use 20W50.
www.saabv4.com | |
|
Joshinator99
Starting Member
USA
39 Posts | Posted - 31 Jul 2017 : 14:42:17
| You could tap in a manual gauge by putting in a tee where the low oil pressure light taps into the block. You didn't say if the low oil light is on?
I am also going to run synthetic 10W-30, but my engine is a fully machined rebuild (forged pistons, etc).
1972 Sonett III | |
|
RhysN
V4 Fanatic
United Kingdom
411 Posts | Posted - 31 Jul 2017 : 18:22:26
| | That seems really low pressure to me unless at idle very warm. Even then I think I would be investigating some. What was done to the engine. | |
|
FromTheKeyboard
Starting Member
USA
39 Posts | Posted - 31 Jul 2017 : 22:43:46
| quote:
Originally posted by RhysN
That seems really low pressure to me unless at idle very warm. Even then I think I would be investigating some. What was done to the engine.
I replaced the following parts:
- Oil pan gasket
- Timing cover (paper gaskets)
- Timing cover oil seal
- Head gaskets
- Coolant pump gaskets
- Coolant pump
- Rocker cover gaskets
Additionally, I only cleaned the cylinder heads of old gasket material, no machining work was done there.
I should probably also mention that I did watch the flow of the oil pump whilst cranking the engine on the starter motor through the oil filter input (filter off), and there was a constant flow of oil through that port.
And assuming nothing is mechanically wrong with my engine, could air bubbles in the oil pressure line cause inaccurate readings? | |
|
FromTheKeyboard
Starting Member
USA
39 Posts | Posted - 31 Jul 2017 : 22:59:50
| Hey, should there be an oil pressure switch screwed into that port, instead of a line leading to an oil pressure gauge?
I'm confused now... |
Edited by - FromTheKeyboard on 31 Jul 2017 23:05:56 | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 31 Jul 2017 : 23:24:50
| There are two types of oil pressure gauge, hydraulic (with an oil line to the gauge) or electrical (switched). Which one do you have? You say there is an oil line, so I assume hydraulic, but if you have the electrical type, does the switch match with the range of the gauge (most likely 0-5 or 0-10 bar)? There should always be a switch for the low pressure light as well.
Low oil pressure is mostly nothing to do with flow rate, unless the pump is really badly worn. The oil pressure is low because the oil "escapes" somewhere at a too high rate (worn bearing, oil pump not tightened to block etc.). Low viscosity oil like 10W30 doesn't help. I would first check the reliability of the gauge you've installed with an external pressure gauge and perhaps change to thicker oil anyway. Have you checked the oil pump when replacing the sump gasket? I would always recommend everyone to do this when installing a new sump gasket, it's a 10 min. job. Inlet and heads torqued down properly?
www.saabv4.com |
Edited by - melle on 31 Jul 2017 23:27:47 | |
|
FromTheKeyboard
Starting Member
USA
39 Posts | Posted - 01 Aug 2017 : 00:02:35
| quote:
Originally posted by melle
There are two types of oil pressure gauge, hydraulic (with an oil line to the gauge) or electrical (switched). Which one do you have? You say there is an oil line, so I assume hydraulic, but if you have the electrical type, does the switch match with the range of the gauge (most likely 0-5 or 0-10 bar)? There should always be a switch for the low pressure light as well.
Low oil pressure is mostly nothing to do with flow rate, unless the pump is really badly worn. The oil pressure is low because the oil "escapes" somewhere at a too high rate (worn bearing, oil pump not tightened to block etc.). Low viscosity oil like 10W30 doesn't help. I would first check the reliability of the gauge you've installed with an external pressure gauge and perhaps change to thicker oil anyway. Have you checked the oil pump when replacing the sump gasket? I would always recommend everyone to do this when installing a new sump gasket, it's a 10 min. job. Inlet and heads torqued down properly?
www.saabv4.com
In that case, I must have a hydraulic gauge (oil line and all that).
I didn't check the oil pump assembly when I disassembled the engine, because I didn't think it would need it.
There are no noticeable leaks around the engine, nor has the oil level changed.
Most of the bolts that had torque values & patterns were all done correctly. Only the rocker cover bolts weren't torqued to spec, purely because I didn't have a torque wrench that small. |
Edited by - FromTheKeyboard on 01 Aug 2017 00:04:36 | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 01 Aug 2017 : 00:23:06
| Rocker cover bolt torque is certainly not an issue here. Not sure about air bubbles in the line to the gauge, I've never had this type. Does the engine still have the oil pressure light switch installed?
www.saabv4.com | |
|
Joshinator99
Starting Member
USA
39 Posts | Posted - 01 Aug 2017 : 00:40:17
| quote:
Originally posted by FromTheKeyboard
Hey, should there be an oil pressure switch screwed into that port, instead of a line leading to an oil pressure gauge?
I'm confused now...
When you add a gauge, you use a brass tee so that you can run both the low pressure switch plus the gauge of your choice.
1972 Sonett III | |
|
FromTheKeyboard
Starting Member
USA
39 Posts | Posted - 01 Aug 2017 : 00:58:16
| quote:
Originally posted by melle
Rocker cover bolt torque is certainly not an issue here. Not sure about air bubbles in the line to the gauge, I've never had this type. Does the engine still have the oil pressure light switch installed?
www.saabv4.com
I am currently running the engine on a custom 2x4" wood structure, for tuning, so everything is kind of mounted wherever it'll work.
And just to make sure my gauge isn't the fault here, I ordered an oil pressure sensor as well.
| |
|
RhysN
V4 Fanatic
United Kingdom
411 Posts | Posted - 01 Aug 2017 : 08:14:57
| Air bubbles in the line don't affect the reading at all, so it's not that if there is a low reading. In general a hydraulic gauge, as you have, should be reading what it sees, they are very rarely inaccurate. Leaks from the gaskets and such which you replaced (and don't have any leaks anyway) do not give rise to low pressure. The sump has no pressure, and the others don't see pressurised oil either.
Normally, as Melle has said, the pressurised oil must be "escaping" somewhere internally. Personally, my first step would be to take the sump back off, and check the oil pump to the block. There were questions on the forum a week or two back about that. As you have no idea what the pressure was like before you did the work there is no way to know whether it had low (ish) pressure before your work. Equally as you haven't looked at balance bearings, nor the mains and big ends, you don't know if there is an issue there. They would be the main areas which see pressurised oil, and wear there is what drops the pressures. Or a worn pump. FWIW the "test" you did doesn't tell you anything to help this.
You aren't doomed, and you are doing the right thing investigating while it's easy!
Have you run the revs higher to see what happens to the pressure? I would expect to see better than 40 psi above 2000rpm. | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 01 Aug 2017 : 10:17:41
| I assumed the engine was in the car, but since it's not: as Rhys already suggested, check the balance shaft bearings if you haven't done so already. These are much more likely the culprit than the oil pump, those are pretty bomb proof.
www.saabv4.com | |
|
fuling
Starting Member
Sweden
32 Posts | Posted - 01 Aug 2017 : 13:54:50
| Begin to check that the oil pressure gauge shows correctly.
Just to rule out the simple, ridiculous things.
Getting so much trouble if you disassemble the entire engine and then it is the oil pressure gauge.
I would say about 1bar at 800-1000rpm
At 2000rpm more similar to about 2bar.
You have more than 0.3-0.6 bar just on driving the starter.
The ignition turned off, the spark plug removed. | |
|
| Topic | |
1.5L V4 Oil pressure
