Need advice on a couple of 951 issues
11-13-2007, 01:45 PM
#1
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Need advice on a couple of 951 issues
I have a couple of issues going on with my '86 951. Everything under the hood is currently stock. If you think you know what the problems could be, please share your wisdom! 
1. Oil leak. It is a very slow leak when the car is parked on a level surface (not enough to leave a drop on the floor, but enough to cause smoke to billow out from under the hood if I leave it sit for a week and then start it up). I don't see any oil on the headers, so I guess it's burning on the cross-over pipe? Also, if I put the front of the car up on ramps, the leak gets much worse, and leaves a puddle on the floor. Would this indicate rear main (crank) seal, or oil pan gasket leak, or something else? I used to have a cam cover gasket leak that was dripping right on the headers, but I had that fixed about a year ago at the dealer.
2. Acceleration seems to have fallen off recently. The boost gauge (stock) shows good boost (almost 2 bar at a little over 3k rpm), but the car isn't hustling quite like normal. The boost seems to come on softer (feels almost like an NA car, especially in 3rd or 4th gear). Wondering if it could be the diverter/blowoff valve, the wastegate, the cycling valve, or a vacuum leak (or something else). I've been thinking of upgrading some or all of these parts sometime. What order should I replace them in, from a troubleshooting perspective (not so much from a $/hp perspective)?
Also, don't know if this could be related, but I recently installed a new head unit, and there seem to be grounding issues somewhere, because I hear engine noise through the speakers when I have the radio on (but not CD). Could a bad ground cause the engine to not pull as hard?
1. Oil leak. It is a very slow leak when the car is parked on a level surface (not enough to leave a drop on the floor, but enough to cause smoke to billow out from under the hood if I leave it sit for a week and then start it up). I don't see any oil on the headers, so I guess it's burning on the cross-over pipe? Also, if I put the front of the car up on ramps, the leak gets much worse, and leaves a puddle on the floor. Would this indicate rear main (crank) seal, or oil pan gasket leak, or something else? I used to have a cam cover gasket leak that was dripping right on the headers, but I had that fixed about a year ago at the dealer.
2. Acceleration seems to have fallen off recently. The boost gauge (stock) shows good boost (almost 2 bar at a little over 3k rpm), but the car isn't hustling quite like normal. The boost seems to come on softer (feels almost like an NA car, especially in 3rd or 4th gear). Wondering if it could be the diverter/blowoff valve, the wastegate, the cycling valve, or a vacuum leak (or something else). I've been thinking of upgrading some or all of these parts sometime. What order should I replace them in, from a troubleshooting perspective (not so much from a $/hp perspective)?
Also, don't know if this could be related, but I recently installed a new head unit, and there seem to be grounding issues somewhere, because I hear engine noise through the speakers when I have the radio on (but not CD). Could a bad ground cause the engine to not pull as hard?
11-13-2007, 02:01 PM
#2
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First - how many miles on the car and how has it been used (street driven vs. occassional track duty vs. primary track car)?
The best way to diagnose the oil leak is to get under the car with a flashlight and start looking around. Chances are you will be able to trace where the oil is coming from. A leaky oil pan gasket and rear main seal are both likely culprits from what you have described...so is a leaky end cap on the lower balance shaft housing.
The acceleration problem could be a number of things, so you need to prioritize where to start troubleshooting for the actual cause of the problem. My knee-jerk reaction would be to start with the cycling valve or search for a vaccuum leak...but this is without knowing more about your car. You can buy a pressure tester pretty cheap to help you search for vaccuum/pressure leaks (check out Arrnworx tools). I doubt that a bad ground wire near your head unit would affect the driving characteristics of the car.
Hope this helps...good luck.
The best way to diagnose the oil leak is to get under the car with a flashlight and start looking around. Chances are you will be able to trace where the oil is coming from. A leaky oil pan gasket and rear main seal are both likely culprits from what you have described...so is a leaky end cap on the lower balance shaft housing.
The acceleration problem could be a number of things, so you need to prioritize where to start troubleshooting for the actual cause of the problem. My knee-jerk reaction would be to start with the cycling valve or search for a vaccuum leak...but this is without knowing more about your car. You can buy a pressure tester pretty cheap to help you search for vaccuum/pressure leaks (check out Arrnworx tools). I doubt that a bad ground wire near your head unit would affect the driving characteristics of the car.
Hope this helps...good luck.
11-13-2007, 08:13 PM
#4
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11-13-2007, 10:46 PM
#6
Three Wheelin'
I'll second the gasket at the rear of the cam tower (where the engine lifting bracket is) and if none of the other things mentioned, maybe a clogged cat?
11-14-2007, 01:30 PM
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11-14-2007, 01:56 PM
#8
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Well, I guess that would be a relatively easy fix compared to the rear main seal or oil pan gasket. Is there a better cam cover gasket available so this doesn't happen again (if that's what it is)?
11-14-2007, 02:14 PM
#9
Dan, what were you thinking with that advice? 
I don't know about the rear cam tower being the cause of the oil leak. Yes it could be leaking but I would lean more towards the oil pan or rear main seal if when you jack it up you get a puddle from it, that would indicate the leak coming from someplace where a lot of oil sloshes up against when jacking up. But yeah you definately need to get under there with a work light and see if you can tell where its coming from.
As for the acceleration issue, one cause could always be the simple fact that your use to the car and it doesn't feel fast anymore. But if it is something mechanical the diverter valve is pretty inexpensive to replace and I think there is a test for it if you wanted to do that. I would also second what someone else mentioned with a clogged cat.
I don't know about the rear cam tower being the cause of the oil leak. Yes it could be leaking but I would lean more towards the oil pan or rear main seal if when you jack it up you get a puddle from it, that would indicate the leak coming from someplace where a lot of oil sloshes up against when jacking up. But yeah you definately need to get under there with a work light and see if you can tell where its coming from.
As for the acceleration issue, one cause could always be the simple fact that your use to the car and it doesn't feel fast anymore. But if it is something mechanical the diverter valve is pretty inexpensive to replace and I think there is a test for it if you wanted to do that. I would also second what someone else mentioned with a clogged cat.
11-14-2007, 04:12 PM
#10
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Thread Starter
Dan, what were you thinking with that advice?
I don't know about the rear cam tower being the cause of the oil leak. Yes it could be leaking but I would lean more towards the oil pan or rear main seal if when you jack it up you get a puddle from it, that would indicate the leak coming from someplace where a lot of oil sloshes up against when jacking up. But yeah you definately need to get under there with a work light and see if you can tell where its coming from.
As for the acceleration issue, one cause could always be the simple fact that your use to the car and it doesn't feel fast anymore. But if it is something mechanical the diverter valve is pretty inexpensive to replace and I think there is a test for it if you wanted to do that. I would also second what someone else mentioned with a clogged cat.
I don't know about the rear cam tower being the cause of the oil leak. Yes it could be leaking but I would lean more towards the oil pan or rear main seal if when you jack it up you get a puddle from it, that would indicate the leak coming from someplace where a lot of oil sloshes up against when jacking up. But yeah you definately need to get under there with a work light and see if you can tell where its coming from.
As for the acceleration issue, one cause could always be the simple fact that your use to the car and it doesn't feel fast anymore. But if it is something mechanical the diverter valve is pretty inexpensive to replace and I think there is a test for it if you wanted to do that. I would also second what someone else mentioned with a clogged cat.
I think what you said makes sense... if it were a cam cover gasket, that wouldn't leak when the car is turned off, even if I have the front on ramps, right? There's not enough oil up there to leak out when it's not running/pressurized, unless there's something I don't understand.
I guess I'll have to get under the car with a flashlight like everyone's saying. Need to put on my new 968 M030 sways anyway!
11-14-2007, 09:33 PM
#11
Three Wheelin'
There is actually quite a bit of oil that builds up in the cam tower. Have you ever removed one? Oil runs everywhere. It was just another suggestion for a possible leak location. Until he cleans it up and starts to investigate with a very strong light source, we are all guessing.
11-21-2007, 04:58 PM
#13
oil leaks
You can use a inspectors mirror that pivots to check if the oil leak is coming from the cam tower end cap, you will see it run out and down the corner of the head onto the header. The fuel filter on my car became plugged after running it low in between buying gas which not only resulted in sluggish starts/ take off from a stop but horrible gas milage. I would start with it and looking for the always present vacuum leak. It does not thae a very larg leak to screw things up.