Check out my leak down / compression test numbers

[Super_Dave_D]

So I have an 88 Carrera I bought 2 years ago. Since then I have replaced the entire interior, full brakes, tie rods, chip exhaust and a ton of other stuff. I know full well that I will never get the thousands I spent back out of it but I don’t care – I love it.

That was until I started burning a lot of oil – 400mi/qt. So I take the car to my wrench (that I rarely use) and he does a leak-down and compression test. He gives me the number and says the results look good but based on the oil consumption, it needs a top end. I thought that the tests would definitively show something.

Look at the numbers and tell me what you think. Help me understand what I am seeing.

CYL COMPR LEAKDOWN
1 155 10%
2 140 15%
3 150 20%
4 150 10%
5 140 17%
6 155 10%


It looks like I will go ahead and have the top end done but I am not too thrilled. I appreciate your thoughts.

Right now I am frustrated to a point that I am considering moving on when I get it back. Does anyone else get that and will I get over it.

[snbush67]

Get a second opinion from a recommended wrench. The compression numbers are the same for each opposing cylinder?...wierd.

Are the numbers from a cold test or was the engine warm?

How much did the mech quote you for a rebuild?

Did you notice a loss in power or just oil consumption?

[88-diamondblue]

I was at about 600 miles a quart when I did a valve adjust and found 2 broken head studs. Pretty upset when I found it. I did a total rebuild and it was one of the best experiences that I have had with the car. Expensive, but am looking forward to doing it again someday. The compression and leakdown will not show valve guide wear. The Carrera is well known for valve guide wear. How many miles on the car? My 88 was ready for guides at 82000 miles. The number seem strange being the same on opposite cylinders.

Here is what it looked like when I started


After and Yes it was worth it

[Bobboloo]

Michael is right. Oil consumption is the important thing when considering valve guide wear although your numbers don't look to good either. Hopefully your P+C will still be with in spec so you can reuse them.

I know the news is not good but look at the bright side. It's better to be aware of the situation and take preventative measures before you drop a valve head and destroy your motor which is the risk you run if you keep driving with that kind of oil consumption.

[schoward]

I had consumption of a Qt. per 600-700 miles and some rough leak down numbers (not too far from yours) on my 81 SC 3.0 l.

Had a top-end done a few winters ago and after the initial financial pain, happy that my SC runs like a top - better and stronger than before. Now burns a QT maybe every 2000-2500 miles. Motor seems very strong and leakdowns at 2%.

I guess point is - it may cost you but outcome may be a stronger, more reliable motor that will last for many years. not a bad thing if you want to keep the car; par for the course.

[ianc]

If the oil consumption is coming from the guides (most likely), then that will not show in the compression and leakdown tests. Your compressions are not bad in that they are relatively close to each other, but the leakdown #'s are not good. It is most likely valve problems, and your mech should have been able to determine whether it was rings or valves (and which ones) when he did the leakdown.

Don't get too discouraged about this. It's not a question of 'if', but rather 'when' this is going to happen. Your number just happened to come up. Looks a little daunting right now, but it's well worth fixing. If you really love the car, as you seem to, then you'll feel great if you have the work done and the car runs like a watch afterward. If you do it yourself (with the proper guidance), you'll feel even better and so will your wallet.

Good luck and don't lose heart; it comes with the territory,

ianc

[dad911]

Did the wrench doing the leak-down test tell you where it was coming from? if it is valves, you can hear it out the exhaust or intake, and rings you could hear it out the breather.

[Porsche_monkey]

Mileage?

Get a leakdown test.