Moonraker

This happened after a 40 minute drive during which all looked normal, the temperature guage at the end of the drive was reading just past the 9:00 o'clock mark. During the drive the oil pressure looked normal. Sitting in the driveway on my return with the enging at idle the idiot light came on and the oil pres read 0, increasing the RPM at first increased pressure but after a few seconds the pressure dropped to 0 and I shut the motor off. The only other thing I noticed on the drive was that the oil Qty, shown on the guage, did not drop to the bottom of the range as it usually does on acceleration.

Oil pump failure in my experience ususaly shows effects much sooner after start up.

I'm no expert on dry sump systems and would apreciate any insights as to what the cause might be. What would the symptms be for instance if the oil cooler loop was blocked and the thermostat opened???

ZAMIRZ

Before you get too upset, at least change the gauge's sending unit to make absolutely sure you are getting a proper reading.

Bill Wagner

Out of curiousity, how many miles are on the car? D

I have to agree with the other poster who said you should be wary since you have BOTH the light and the meter showing low pressure. Also, since the level doesn't drop on the oil level indicator, it really sort of implies the oil isn't being pumped out ..... as in either some major clog or a pump failure. I wouldn't think a clog would happen instantaneously. I also wouldn't think that a clog in the cooler would do this, because the oil is, if I'm not mistaken (AND I MAY BE MISTAKEN) the oil circulates in more than one path even if the cooler was clogged.

Hope this helps,

Adrian

Dear Bob,
I would recommend you do some troubleshooting first before you start changing things.
The oil level sender is best left alone.
You have an oil pressure warning which means you have no oil pressure.
The oil pressure will drop to 0 if it is too hot.
You have to confirm that the oil cooler thermostat is opening.
Is the oil circulating to the oil cooler?
Is the oil cooler fan functioning?
When was the filter last changed?
When was the oil last changed and what oil are you using?
The last thing you even think about is the oil pump. These things are pretty well bullet-proof.
Start cheap and work towards expensive.
Confirm the operation of the all components in the oil lubrication system first.
Ciao,
Adrian.

Shaun Leahy

Bob,
I worried big time when this happened to me after tracking the car last Summer. Now solved the problem though.

Revs were over 6,000 on/off during the day and afterwards oil pressue dropped below 1, so central warning light came on when revs dropped. Rasing the revs raised the pressure and turned off the warning light. However the problem returned when braking to stop, when the engine revs dropped.

The guages showed oil going into and out of the tank. So the oil pump was not my problem: my oil level guage worked (went down at high revs, went up at low revs as oil drained out). An engine rebuild was mentioned as a possible need and I went numb, but as Adrian says start cheap.

My probelm was solved by mechanic who checked the oil lines and found a Valve blocked with dirt (pressure relief valve I think). He cleaned it out and replaced the oil, did the trick. No such problem since. The expensive part of the repair was the labour charge (GT-One, Chertsey) but I was happy. Condition very similar to yours by sound of it.

Shaun Leahy, 92 C2 TIP

Moonraker

Thanks for all the sugestions. I will work through Adrian's checklist this evening and hopefully figure out what the problem is. Answers to questions :

Car has 130 K miles, oil is Mobil 1 and was changed 100 miles ago as was the filter.

Adrian

Low oil? Not the first time this has happened.
Ciao,
Adrian.

DaveK

Why would low oil cause the oil level gauge to be reading higher than usual when driving?

Moonraker

10 plus quarts went in and none has come out , except the drips of course.

Adrian

I ignore any comments made regarding the oil level sender.
I do not consider anything said or written about th eoil level sender to be helpful when troubleshooting. It only serves one purpose and it does not do that very well. I have seen a nice oil level with only 6 litres in the engine.
I have seen no oil levle when the engine is filled with 10 litres.
In reality once that oil is foamed up in the tank the sender will float on the foam. Very hot oil, low oil, lots of foam, very low oil pressure but nice oil level on the instrument when you stop on level ground with the engine at idle blah blah blah.
Ciao,
Adrian.

Moonraker

Well some good news. With great trepidation I started the car this morning. When cold, oil presure looks normal. 3 bar at idle and limiting at 5 bar with the rpm at 3k. I did not have time to warm the engine up but wil try that tonight.

My current theory after having reviewed the schematic of the oil system in Adrian's book is as follows: The thermostat is only partially opening which is blocking the return path for the oil, with oil starvation on the input side to the pump the presure drops to zero.

I will pull off the rocker covers tonight and see if I can determine whether the thermostat is directing oil to the cooler.

Moonraker

Pulled the rocker cover off to get access to the thermostat. Idled the engine and alowed the oil temp to slowly rise. No change in pressure until the temp needle passed the 8:00 o'clock position then the pressure started droping the thermostat did not open the circuit to the cooler. As the thermostat is the only temperature sensitive element in the system I am going to assume that it is kaput. A new one is on order and I will let the board know the results when I get it fitted.

Rgds

Dunasso

Nice detective work there Moonraker, hope that your problems are solved. A word of caution though, be careful when installing the new thermo. assm. the threads can easily be crossed.
Good Luck,

Duncan

DarrylH

There have been several revisions of the t'stat, not all of which have the same routing for the hoses. If you get a later one, you may need some ancillary parts to make it all fit correctly. I think my mechanic said there was some supplementary info in PET? I'm no expert, just a heads up, my car sat on a hoist for a week while they waited for the bits they'd missed ordering in the first place. FWIW...

JasonAndreas

From reading your post I'm not sure if you realize that you only need to replace the thermostat insert and not the whole thermostat, its a hell of lot cheaper and easier...