964 C4, how spooked would you be...
 

By a car where the owner is disclosing a low oil pressure (below 1bar) at idle.

Here's the ad for the car:
1989 Porsche 911 Carrera4 Coupe - Alberta Cars For Sale - Kijiji Alberta Canada.

The owner has disclosed that when warm, it shows <1 bar at idle. Above 1000 rpms, pressure is fine.

In researching the car, I've come across a previous ad for it (by the previous owner):
http://forums.pelicanparts.com/canada/460991-fs-my-1989-964-carrera-4-16-999-00-a.html

and what seems to be some threads started from a previous owner:
http://forums.pelicanparts.com/porsche-964-993-technical-forum/349057-oil-pressure-light-comes-when-engine-hot-idling.html

After a fair bit of reading, I see many posts here and on Rennlist from several 964 owners who have low oil pressure at idle, but still... spooky.

Thoughts?

Sounds like it needs 20000 worth of motor work , for starters..........

I did not read all the attached threads. Low pressure at idle could be as simple as pressure sender. Mine would trip the warning light at stop lights. Recently changed out sender and now no issues.

You realize that this behavior is acknowledged as normal in the Owner's Manual, right?

yep. that's one of the things that has me on the fence. Issue with this on is that it happens consistently, once the car is warmed up... not occasionally. Also, the fact that a mechanic checked the oil pressure at idle and it really is under 1 bar.

Over the past few nights, I've trolled through threads here and on Rennlist. There are definitely other prople with 964s that occasionally get the oil pressure light... but the fact that this one actually measures below 1bar @ idle concerns me.

Do you know what oil he's using? The gauge is sensitive- I can see a change immediately when I add 500ml of top-off oil.

The oil light on - at idle - is normal ?
I don't think so.

Beat around the bush all you want on this one.
Low oil pressure, confirmed via external gauge = trouble.
trouble = opening case = 20000 dollars, min.

Don't know what the current owner is running, but looking at the threads started by two previous owners on pelican and rennlist, I know it was running 20w50 and still getting the low pressure warning, and still confirmed by a mechanical gauge.

one of the things I've been looking at the last few days is the availability of low-mileage or recent rebuilt 3.6 engines or longblocks. In the past 3 months or so, there have been 3 for sale from 5-8k. I would consider this car if I could buy a replacement engine right away and still be under 20k upside to that would be having the car, good engine + rebuildable spare. Downside is that I don't know if I want the drama.

I really like the car... My favorite color and the fact that it's already in Canuckistan makes it a lot easier logistically. Again, just not sure I need the drama/fiasco.

Ikd love it if he changed the oil pressure relief valve and found that fixed it, but I guess I'd still worry about the effect of low oil pressure over the past 4+ years

Owner's manual indicates it's not abnormal:

"The oil pressure should be at least 3.5 bar at an engine speed of 5,000 rpm. When the oil is hot, the red oil pressure warning light may light briefly at idle without endangering the engine." (P43, 1990 C2/C4 Owner's Manual; emphasis added)

agreed. The question is whether it's a problem when "may light briefly" becomes "lights up every time the car is warm and idling". I dunno, I haven't owned one before. This car has A LOT going for it (for me anyway), but the oil pressure thing has me spooked

Pedantic arguments aside, unless it was a screaming deal I'd probably pass. Not only is there the threat of ex$pensive engine work, the *fear* of expensive engine work would be in the back of my mind every time I romped on the gas pedal, which would seriously compromise my enjoyment of the car.

$0.02,
Robert

Total neophyte question: regarding the estimated $20K to open up and repair a 964 motor, is it a significantly more expensive engine to overhaul than, say, a 3.0 SC or 3.2 Carrera motor?

3.6s are not that much more to rebuild than earlier ones. $20K seems awful pricey to me.
And 964 oil pumps are subject to wear/distortion more than earlier ones so that could be a reason too.

During the heat of summer, it is not unusual for my oil pressure light to come on everytime I come to a stop with my SC. It's done this for 28 years now. Same engine, same internals, 212k miles. It's consistent with the statement in my owners manual. However for my 993, it never comes on, hot weather or not.

The low pressure setting seems to be model specific. Check with owners of the exact same year and model as the one you're considering and see how their's acts. Maybe try raising the idle ever so slightly and see if it stays off more.

The other question to ask is what activitates the light and is the setting the same on every car. If it is a pressure switch, the answer is obvious. If you really like the car, measure the actual pressure at idle and maybe change out the switch.

The $20k quote is a scare tactic being used for god knows what reason.

Assuming the majority of parts in the bottom end are fine, it will not cost $20k.

New bearings, some machine work, seals/gaskets, and probably a few odds and ends has you looking at maybe $13k to $15k.

Scare tactic?
Please elaborate.

well for some reason, you seem to think cracking the case is going to result in $20k worth of work.

Do you have even the slightest bit of support for this figure?

Sure, if he needs new P&Cs, new rods, and a bunch of other stuff, it could result in that.

Most likely, he's got some worn bearings along with typical wear in other areas.

To suggest that anytime you open the case you are looking at $20k seems to be an attempt to scare this person away from buying the car, hence scare tactic.

my "slightest" bit of support?
how about an invoice, dated
November 2011?