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'97 Concours--Oil Pressure Problem


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Earlier this afternoon, I was sitting at a stop light when I heard a warning chime and received a rather dire sounding message to stop the engine because the oil pressure was low, so I pulled into a nearby parking lot, checked my oil, and dipstick appeared to be dry, although it's hard to tell with those plastic-tipped dipsticks. I like the old fashioned flat metal ones better; they're much easier to read.

Fortunately, I had a couple of quarts of oil in the trunk, so I poured one in and drove home. On the way, the oil light on the dash would intermittently blink on for a second or two, then go back out for maybe 10 or 15 seconds. When I got home, I let the car sit for a couple of hours and then checked the oil again. This time, the plastic tip of the dipstick appeared to be completely wet with oil. I checked trouble codes and found nothing new, just the same "History" codes that have been there for months and are relatively harmless and have absolutely nothing to do with with the engine or the oil.

The DIC shows about 30 percent of oil life left. Last time I had the oil changed, when the DIC flashed a warning that the oil level was low and showed about 20 percent oil life remaining. I took it to a full service garage that I trust and asked the mechanic who changed the oil to check for any obvious oil leaks. He reported none and said the crank case appeared to have a normal amount of oil when he drained it.

So my hypothesis is that the car is burning a little bit of oil. This could be supported by the fact that the car puts out a puff of white smoke from the exhaust when I first crank it up. For reasons unknown, the car is also very hard to crank, taking about 10-15 seconds on the starter, but it runs beautifully once it gets going.

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Ok there is a lot here to discuss

Do you do WOTs?

What grade and type of oil are you using?

At the end of the oil life the oil can become thinner, I would change the oil and use DINO 10W30 for high mileage engines, the high mileage formula has conditioners for the seals.

While no one agrees with me, laugh.gif, I have a theory that the engine can leak or bleed oil pressure internally at the case half seal, if it can leak externally, it certainly can leak internally, not only via a cracked seal or one with a void blown out of it. I so want to take one of these engines apart to see how it wears. I was stunned when I saw how badly the crossover seals aged/wore out, cracked, deformed, with missing pieces (perfect for clogging the coolant air purge orfice). I had my 96 sitting dormant with no oil or coolant in it for about 6 weeks and when I finally started it, I had low oil pressure immediately, I cant help but think that leaving it without oil I caused the case half seals to shrink, it never got better I ended up using 15w40 till I got rid of it.

Are you leaking oil?

Sometimes the crank pulley is not torqued correctly and cause this, it drives the oil pump, a retorque of the crank pulley might help

You might check your oil pressure sender for leaks and bad connections and consider changing it, it is attached to the oil filter adapter

If this low pressure continues you can consider using 15W40 diesel oil (Rotella), its thicker and will provide more pressure at idle

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Thanks for your response--

-I don't know what a WOT is, so I can't really say whether I do them or not.

-I'm running 10W30 in the car, but I'm not sure of the brand. It's whatever my mechanic uses in bulk. The quart I put in yesterday was a high-mileage formulation. The car just turned 90,000, btw.

-I haven't noticed any oil leaked on the ground, but I live in an apartment complex, so I seldom park in the same spot twice in a row.

-I did drive the car last evening and the oil light did not come on.

Ok there is a lot here to discuss

Do you do WOTs?

What grade and type of oil are you using?

At the end of the oil life the oil can become thinner, I would change the oil and use DINO 10W30 for high mileage engines, the high mileage formula has conditioners for the seals.

While no one agrees with me, laugh.gif, I have a theory that the engine can leak or bleed oil pressure internally at the case half seal, if it can leak externally, it certainly can leak internally, not only via a cracked seal or one with a void blown out of it. I so want to take one of these engines apart to see how it wears. I was stunned when I saw how badly the crossover seals aged/wore out, cracked, deformed, with missing pieces (perfect for clogging the coolant air purge orfice). I had my 96 sitting dormant with no oil or coolant in it for about 6 weeks and when I finally started it, I had low oil pressure immediately, I cant help but think that leaving it without oil I caused the case half seals to shrink, it never got better I ended up using 15w40 till I got rid of it.

Are you leaking oil?

Sometimes the crank pulley is not torqued correctly and cause this, it drives the oil pump, a retorque of the crank pulley might help

You might check your oil pressure sender for leaks and bad connections and consider changing it, it is attached to the oil filter adapter

If this low pressure continues you can consider using 15W40 diesel oil (Rotella), its thicker and will provide more pressure at idle

The secret to flying is to throw yourself at the ground--and miss!

--Douglas Adams Life, The Universe, and Everything

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I took the car to Precision Tune for an oil change this afternoon and got some disheartening news. Apparently the seals are gone on the upper oil pan. While this is not a major repair in and of itself, getting to the darn things is. According to the guy at Precision Tune, it requires pulling the engine out of the car and, according to the shop manual, is about a 20-hour job. When you multiply that by dealership labor charges, it's out of my price range to fix. I'm not sure what I'm going to do now, but I'm open to suggestions.

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I'm no critic, but did this mechanic tell you HOW he came to that conclusion? That seems like a hard thing to determine for sure without pulling the oil pan and checking the seal. Also, it seems to me (correct me if I am wrong) that if the seal was in fact gone, that you would be leaking oil like a sieve. Check out all your pan bolts to see if they are torqued to spec. If any of them are loose or broken get them taken care of...then see if the problem goes away. Either way, I would eliminate any and all other possibilities before you condemn it.

Mike, I DO agree with your theory. I have a pretty bad leak, 3 quarts or so between oil changes, and since the leak started getting real bad, every so often I get the chime of doom and the "stop engine. low oil pressure" message. I shut the car off, let it sit for 5 minutes or so, start it back up and it's fine. It usually goes weeks between episodes. I can't fix the leak in mine right now though...so I've just learned to live with it. Someone should seriously look into that theory though. It seems totally logical to me.

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To be honest, I don't know how he came to that conclusion. The guy who told me all this was the manager who spent most of his time at the counter writing up service tickets. I think he was relaying information from the technician who worked on the car. He did show me the underside of the car and there was lots of oil dripping down the outside of the oil pan. He did say specifically that the leak was in the upper oil pan. The oil leak must be fairly significant as the oil light was blinking on intermittently by the time I got the car home from the shop. Is it possible to get to those bolts and inspect/tighten/replace them without pulling the engine? That would be a major relief if it weren't as bad as I've been led to believe.

I'm no critic, but did this mechanic tell you HOW he came to that conclusion? That seems like a hard thing to determine for sure without pulling the oil pan and checking the seal. Also, it seems to me (correct me if I am wrong) that if the seal was in fact gone, that you would be leaking oil like a sieve. Check out all your pan bolts to see if they are torqued to spec. If any of them are loose or broken get them taken care of...then see if the problem goes away. Either way, I would eliminate any and all other possibilities before you condemn it.

Mike, I DO agree with your theory. I have a pretty bad leak, 3 quarts or so between oil changes, and since the leak started getting real bad, every so often I get the chime of doom and the "stop engine. low oil pressure" message. I shut the car off, let it sit for 5 minutes or so, start it back up and it's fine. It usually goes weeks between episodes. I can't fix the leak in mine right now though...so I've just learned to live with it. Someone should seriously look into that theory though. It seems totally logical to me.

Edited by human

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I would be very careful

What does he mean by the UPPER OIL PAN?, is he referring to the case half seal?

A leak at the oil pan will not cause low oil pressure, just a leak, you might be able to re-torque the pan bolts to spec

You could have a leak at your oil pressure switch, they often leak, and THAT would cause a low oil pressure light if the switch was defective, plus they leak, and wind would blow it back over the engine

Pre-1995 - DTC codes OBD1  >>

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He specifically used the term "upper oil pan". He said the engine has a dual oil pan and the leak is coming from the upper one. Maybe he didn't know what he was talking about. A fairly generous amount of oil has blown over the bottom of the engine. Can these bolts be accessed and tightened to spec without removing the engine? I think I know what you mean about the oil pressure switch. I had a '91 Cutlass Supreme a few years ago that had a leak in the oil sensing unit and caused a low pressure reading as the oil level went down. It was like a $100 repair in the late '90s. That would be great if it were a relatively inexpensive fix.

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I will let Kevin (KHE) respond to this, maybe this is the oil manifold that he talks about, that leaks. Kevin, can a bad oil manifold cause low pressure at idle do you think? I need to pull my manual out and research the oil manifold.

The case half seal is at the split at the mid point of the crank mains.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

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I took the car to a shop that I trust for a second opinion, and it wasn't encouraging. He said the oil pan gasket is leaking "significantly" toward the rear of the engine and the oil sending switch also has "a bead of oil" but is not leaking badly enough to cause the amount of oil loss I appear to be experiencing. Sadly, I'm not holding out much hope for this car.

I will let Kevin (KHE) respond to this, maybe this is the oil manifold that he talks about, that leaks. Kevin, can a bad oil manifold cause low pressure at idle do you think? I need to pull my manual out and research the oil manifold.

The case half seal is at the split at the mid point of the crank mains.

The secret to flying is to throw yourself at the ground--and miss!

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Listen as terrific as these cars are, they can be leakers, I would pay NO attention to a wet bottom unless it becomes too much to control.

Mine was wet the entire time I owned it, ignore it, keep putting oil in it, do WOTs, and drive it hard

Dont worry about leaks, use 15w40 and forget it

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

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If the crankcase half seals are seeping, that won't cause low oil pressure. If the oil manifold plate is leaking, that may cause low oil pressure I suppose as there are pressurized oil passages in the oil manifold plate. It would have to be leaking significantly though - as in spraying out... The oil manifold plate is a 1/8" thick aluminum plate with silicone seals molded into it. It is between the oil pan and the lower crankcase (lower portion of the engine block).

To change the oil manifold plate requires the transmission to be removed - not as bad as removing the engine. Even when the oil manifold plate is leaking, it only results in the bottom portion of the engine being wet with oil and a few drips to the ground when parked overnight. Hardly the catastrophic oil loss the shops are describing...

I would put the car up on a set of ramps and let the engine idle while inspecting the underside of the engine. It might be someting as simple as an oil cooler line o-ring. Do not give up on the car yet.

Edited by KHE

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I have to pull my manual out and see this manifold.

Obviously, low oil pressure can be caused by bearing wear, but the way my low oil pressure started, makes me think its related to a seal. If you recall, I had my car up on jack stands for 6 weeks with no coolant or oil in it, once I reassembled everything, I had low oil pressure problems at idle that I did not have before the job.

I never put an analog gage on the engine, but the results from that would have been interesting to see

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I've got six quarts of oil in the trunk and plan to keep adding it as needed. So far, I haven't needed any. I've driven the car a little more than 100 miles in the past week without any problems. Regular oil checks show the crankcase is still full of oil, although the oil light has flickered on the instrument panel a time or two while sitting at a long stoplight. It goes out and stays out as soon as I start moving. I'm thinking I should replace the oil sensing switch. Is this a complicated procedure? Can it be done without pulling the engine?

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The oil pressure switch is located in the front of the engine to the left of the center attached to the oil filter adapter, if you take the oil filter out, it should be facing the driver side of the engine and have a wire attached to it. Remove the air deflector to get more room. ONLY buy an AC DELCO pressure switch its calibrated for the NS

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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  • 3 weeks later...

Thanks for the diagram. That'll be very helpful. Sorry I've been offline for a while. A couple of weeks ago, I found a nice, clean '95 Pontiac Bonneville for several hundred less than the cost of repairing the Caddy, so my game plan now is to replace that oil pressure switch, dump some stop-leak into the crank case, sell the car (with full disclosure, of course) and let it be someone else's dilemma.

Interestingly, I've driven the Caddy a couple hundred miles since I became aware of the oil leak, and the oil level hasn't gone down noticeably.

Oil pressure switch

The secret to flying is to throw yourself at the ground--and miss!

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That is because, the oil leak is not the major source of your oil consumption. While the bottom of the engine is wet, its seeping, not leaking

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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