SteveNick

As a relatively new owner (89 951) I took my first foray under the car yesterday wrench in hand to replace the Oil Pressure Sending unit. (The gauge was pegged at 5 Bar when I bought the car last August). Posts I've read on the subject suggest a bad sending unit as the most likely culprit.

Spent a couple of hours following the Procedure posted on the 944 Garage. Many contortions later...I started the car up and the gauge was still pegged at 5 Bar.

I'm very sure I have the wires on the correct connectors. I paid particular attention to that element. (per the 944 Garage procedure if the terminals are reversed the gauge will be pegged at 5 Bar and the low oil pressure light will flicker on at idle. I have no flickering of the low oil pressure light). The connections are tight and clean.

Anybody have any suggestions?

Jake951

It is normal for the gauge to peg at 5 bar when starting up cold. However, as the engine warms up, the pressure should drop and eventually settle out at around 2-3 bar at idle.

Danno

Sounds about right. On a cold engine, it should idle at 5-bar. When it's warmed up, idle should show 3-bar and anything above 3000rpm should give you 5-bar.

Peckster

Oh well, those contortions probably helped limber you up, and you got to know your car a little better! I always do a rennlist search before starting a job. It will save you a lot of time and money.

SteveNick

There does seem to be some signs of life. Previously the pressure was pegged at 5 bar regardless of hot or cold engine. Now on start up it is at 5 Bar and when up to temp seems to be between 4 and 5. At no point does the indicator needle drop to the 2-3 range. The needle has never moved at all prior to replacing the sending unit. So something has changed.

It was definitely a learning experience. I've pulled a few things apart now (got them all back together again too!) I'm starting to appreciate just how well these cars are put together.

Does it sound like an electrical problem or a mechanical issue with the gauge itself?

special tool

SteveNick - how did you arrive at your "up to temperature" state?

Jake951

The oil pressure after warmup varies somewhat with oil weight and ambient outside temperature. With 5W30 on a hot day, mine idles at around 2 bar. With 15W50 on a cold day, it's 4 bar.

SteveNick

[quote]Originally posted by special tool:
<strong>SteveNick - how did you arrive at your "up to temperature" state?</strong><hr></blockquote>

"up to temperature" based on the car being at normal operating temperature with the water temp gauge settled in just a hair above the lowest increment.

I'm on the Learning Curve here. Not up to the same level as most of the participants in this forum so I'll probably need some coaching to describe things more helpfully.

Danno

Because of its higher specific-heat, oil takes about twice as long to warm up as water. So take your car out for a drive of at least 15-minutes (assuming ambient temperatures of 70+). Then pull off and check the oil-pressure at idle. It should be around 3-bar.

" I'm starting to appreciate just how well these cars are put together."

Heh, heh... wait 'til you try to change the thermostat....

SteveNick

Danno:

I've only got about a 10 minute run to work each way so based on what you said the oil may not be "up to temperature".

I'll try taking the long way home tommorow night (a longer drive is no hardship) and see what happens when I let it idle.

I'll let you know.

Thanks for the feedback guys. I think I'll have to join up. Seems like a better value than my PCA membership.

jason952

Then, once it really warms up, which is not during a 10 minute drive, then you can hit the boost hard a few times to really get that oil hot!

SteveNick

Didn't get the chance to do the long way home tonight. My wife insisted on going out for dinner at a spot about half way home. (At least she paid)

The local Rennsport chapter is doing a run down to Lake Placid on Saturday. That will tell if the problem is fixed or not.

SteveNick

An update on the oil pressure problem.

Went down to Lake Placid on Saturday (great trip, some real nice roads) and the problem remains the same. Although the gauge now moves between the 5 and 4 Bar marks it never drops below the 4 mark regardless of how long the car has been running.

Any thoughts?

Bri Bro

I don't think you have a problem here, that is how my preasure runs. If you want to be sure, go by a garage and have them remove the sensor and connect a preasure gauge to see what the "real" preasure is.

SteveNick

Interesting. You've been running the same pressure reading for a while and you've had no problems?

The car actually runs great. Being a new owner I get nervous when things don't measure up to the commonly accepted norms.

I guess I'm in Danno's "Worrier" stage of ownership.