LOW OIL PRESSURE. 2006 GRANSPORT. I THINK ENGINE NEEDS TO COME OUT.

[Oxytorch]

For quite a while now, I've been worried about low oil pressure. First noted about 2 years ago, just under 1.25 bar (about 18 psi) at hot idle. Pressure sender was a bit flaky though, so it was replaced along with oil change 1 year ago. However, the new sender showed even lower pressure at hot idle, sometime briefly triggering low oil pressure light when coming to a stop at traffic lights. Following recent oil change using slightly more viscous oil 5W-50, oil pressure is even worse, typically dropping to zero at hot idle. However, no noise from bottom end and no valve train noise. Low oil pressure warning is now coming on sometimes with engine coolant temp of only 70 C. Oddly, on these occasions it will hold 2 bar for 10 seconds or more then suddenly drops to zero. When this occurs, there is a subtle change in engine or exhaust note. At 90 C with zero oil pressure at idle, if I stop the engine then restart, it can hold 1.25 bar for a while before plummeting to zero, again with a slight change in engine/exhaust note. I can't figure out why it does this. Oil pressure is relatively low across the rev range and this hasn't changed recently. I get 2.5 bar (about 35 psi) at 2000 rpm with engine hot. I had a local workshop do a direct pressure measurement: It showed 90 psi on start, steadily dropping to 18 psi at hot idle. After short road test, 18-25 psi when hot. Oil pressure responds well to rpm, maxing out at 75 psi. They noticed some air bubbles on the dip stick. Therefore, I think next step is to take the engine out to inspect lubrication system. If that's not the problem, then engine rebuild... For engine removal and reinstallation, is an SD2/3 needed? I'm thinking of having the local workshop do the job because the only Maserati independent mechanic here doesn't seem interested. The mechanics at the local workshop have worked with V8 supercars teams, and they are prepared to do the job.

 

[Geo]

The figures you quote for direct pressure measurement suggest there is nothing wrong with your engine or its lubrication system. Either the sender, guage or both are giving problems. It could be something as simple as a bad connection at either sender or guage.

 

[Oxytorch]

Oops typo. They got a reading of 18-20 psi at hot idle after short drive. I thought normal pressure is 30-35 psi at hot idle. Also, I’m using mildly heavier 5w50 rather than the 5w40 it replaced recently.

 

[DevonPaul]

Are these reading from the dash gauge, or a plugged in diagnostic?

Before spending ££££ you night want to get the guage checked/replaced.

Paul

 

[philw696]

Paul he states his workshop have taken I direct reading with a capillary gauge so a new sender won't change anything.
I'm wondering if the oil pump shafts have rusted away like what happened on my Project 4200 from a leaking water pump ?
Pressure test the cooling system and see if the pressure falls and if so look carefully around the combined oil/water pump.
My shaft was so rusty and worn it wasn't engaging all the time and causing oil pressure problems.
I repaired the car myself with all the parts from DL Swindon.

 

[Geo]

Phil, am I missing something here? Are the direct pressure readings hot and cold not pretty much where they should be?

 

[philw696]

I agree 75 psi is 5 bar and at rpm above idle hot that's where it should be.
I found running mine on 10W60 gave higher pressure at idle hot than on 5W40 quite considerably.
They are strong engines even after mine suffered pump failure at 90,000 miles.

 

[Oneball]

The bit about a slight change in engine note when the gauge reads zero makes me think that either there is something going on with the oil system or there’s an electrical fault that isn’t just the sender. Did you tell the mechanic about it?

 

[Geo]

The bit about a slight change in engine note when the gauge reads zero makes me think that either there is something going on with the oil system or there’s an electrical fault that isn’t just the sender. Did you tell the mechanic about it?

I forgot about the change in engine note. I like your thinking Oneball.

 

[Oxytorch]

Phil, am I missing something here? Are the direct pressure readings hot and cold not pretty much where they should be?

Although it maxed out at 75 psi, I’m not sure what rpm. On the dash pressure guage, it gets to 5 bar at about 4000 rpm now. When I first got the car, I seem to remember it would be at 5 bar at 2000 rpm.

 

[philw696]

The noise you here is it starved hydraulic lifters.
When I bought mine the independent that had looked after it in Kent condemned the engine.
I bought it blind thinking I was putting another one in.
The noise was the lifters.
I would be investigating further.

 

[Oxytorch]

The bit about a slight change in engine note when the gauge reads zero makes me think that either there is something going on with the oil system or there’s an electrical fault that isn’t just the sender. Did you tell the mechanic about it?

I don’t recall telling the mechanic. The change in engine note is subtle but noticeable to me but I think when you start telling them about subtle things, they often just look at you like you’re imagining things.

 

[Andy Marshall]

I don't know about the internal workings of these engines, but is there some sort of pressure relief valve that could be playing up? If the pump was completely knackered surely you would not get good pressure at any time?

 

[Gp79]

The oil pressure on my GS is just under half gauge at hot idle which would be around 2 bar / 29 psi that's if the gauge is reading accurately.

Where did the workshop connect to get a direct pressure measurement?

If confirmed oil pressure is low and before removing the engine I would look at the following:

Clean oil suction strainer on dry sump tank
Replace oil hose from tank to oil pump, in case it has collapsed / somehow restricting the flow.

 

[CatmanV2]

If someone can confirm the capillary readings are sensible my money is on a short somewhere making the engine load up and the gauge read zero

C

 

[Oxytorch]

The noise you here is it starved hydraulic lifters.
When I bought mine the independent that had looked after it in Kent condemned the engine.
I bought it blind thinking I was putting another one in.
The noise was the lifters.
I would be investigating further.

I don’t think it’s starved lifters. There is no lifter tick at all with engine hot and the oil pressure reading zero. I do get lifter tick occasionally on starting but it goes quickly. I thought the change in engine note might be due to inadequate oil pressure for the variators causing a change in timing but I’m just guessing. Everything sounds smooth when I pop the bonnet to have a close listen.

 

[Oxytorch]

The oil pressure on my GS is just under half gauge at hot idle which would be around 2 bar / 29 psi that's if the gauge is reading accurately.

Where did the workshop connect to get a direct pressure measurement?

If confirmed oil pressure is low and before removing the engine I would look at the following:

Clean oil suction strainer on dry sump tank
Replace oil hose from tank to oil pump, in case it has collapsed / somehow restricting the flow.

Oil pressure tester was connected to the oil pressure sender connection. Getting to it was difficult, needless to say. Where is the oil suction strainer? How do you get to it?

 

[Gp79]

Part number 8 on bottom of oil tank, should be quite quick to check...

everything is hard to reach...

 

[philw696]

There's strainers to each gallery of each oil pump of the combined unit but its a major task to get the pump out insitu as I know.

 

[Gp79]

If there is no engine noise when showing zero oil pressure you would have to think just a faulty reading?

If the pressure was really zero it would be game over pretty quickly.