SaabCentral Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
515 Posts
Discussion Starter #1
1995 9000 Aero B234R. First oil change on her and after driving a round for a bit the oil light has started to come on at idle. It will turn off as soon as throttle is applied.

Any ideas whats going on?
 

·
Registered
Joined
·
515 Posts
Discussion Starter #2
one piece of information. the new oil is Mobil 1 5W-30

The previous owner said he always used Shell Rotella T6
 

·
Registered
Joined
·
2,026 Posts
one piece of information. the new oil is Mobil 1 5W-30

The previous owner said he always used Shell Rotella T6
Rotella T6 comes in two different formulas.

1. Full Synthetic Diesel formula - intended for diesels engines only. It is available in three viscosity ratings, 15W-40, 5W-40 and 0W-40.

2. Multi Vehicle formula - for gasoline engines as well as diesel engines. This blend is only available in one viscosity rating - 5W-30.

Assuming that the PO was running the Multi Vehicle blend, its probably a safe bet that a difference in viscosity isn't the issue.

While the early problems with Mobil 1 and seals have long been solved, synthetic oils still have a tendency to flush years of built up deposits from the system. They end up in the sump and are picked up by the oil pump. After the oil leaves the pump, it goes directly to the oil filter where the deposits are filtered out.

I would try changing the filter - and maybe consider cutting it open to inspect the pleats for excess/premature fouling.
 

·
Registered
Joined
·
515 Posts
Discussion Starter #4
Alright so just changed oil and filter again , this time with 40 weight Mobil 1. Drove around for a bit , and the light came back on at idle after about 30 minutes of driving

Darn
 

·
Registered
Joined
·
2,026 Posts
Alright so just changed oil and filter again , this time with 40 weight Mobil 1. Drove around for a bit , and the light came back on at idle after about 30 minutes of driving

Darn
It seems strange that an oil change would cause a sudden drop in oil pressure - to the point that it cannot open the contacts in the switch. Whenever the ignition switch is in RUN, the warning lamp in the cluster is supplied with 12 volts on one side. The other leg is connected to the pressure switch. The body of the switch is grounded through the block.

With the key in RUN and the engine is not running, there is no oil pressure to open the switch contacts. The light is lit.

When the engine is started and oil pressure is established the contacts in the switch open, the path to ground is broken and the light goes out.

If the switch is good, that make/break point occurs at about 5 psi.

Two thoughts:

1. Although the switch is supposed to snap open and closed at 5 psi, over time they can go out of calibration (weakened spring, internal leakage, etc.)

2. Whenever I am getting a questionable low oil pressure warning, I visually confirm oil flow to the most remote part of the lube oil system. Generally that point is the rocker arms/cam followers.



On most vehicles to check that oil is getting to the most remote point is easy. Just open the oil fill cap on the valve cover and look in. If you see oil splashing around, you can be fairly certain that the system has sufficient pressure. With that information in mind, you can rest easy and take your time to change the switch.

Problem is the design of the B234 valve cover - there is no oil fill cap to remove and look down. The only place to attempt to check for the presence of oil to the can followers is the PCV port on the rear RH side of the valve cover.




The switch is way down behind the starter.
 

·
Registered
Joined
·
515 Posts
Discussion Starter #6
Thanks Chengy... one other thing is that the light will only come on when the car is at full operating temp and it’s quite hot out. The light won’t come on if I just go for a quick 15 minute drive.

Either way seems I should pick up a pressure tester.
 

·
Super Moderator
Joined
·
2,983 Posts
While it is uncommon on T5 B motors, I think dropping the pan and cleaning out possible sludge or ground down timing / balance chain guide bits will be in your future. It doesn't spell the end of the engine (or even the timing system) but I've had to do it before.
 

·
Registered
Joined
·
1,112 Posts
Oil pressure Warning light switch used on Saabs is Usually Bulletproof.
Did have one on my '84 that leaked a bit of oil tho.
The oil warning light at idle.. traditionally.. indicates a worn out engine.
Fair chance your 'new to you' car buy was filled with STP.
Your oil change dumped the Swill.
SERIOUSLY suggest fitting a decent Oil pressure gauge to the Oil gallery and reading the actual oil pressure.
Anything else is naive conjecture.
 
1 - 8 of 8 Posts
Top