compression test results

[BlueOvalBill]

My "service engine soon" light has come on (and gone off) a few times over the past few months. I took the car to the dealer. They ran a compression test and found that cylinders 7, 2, 6, and 5 have relative compression losses of: 5%, 1%, 5%, and 11%. They recommend replacing the driver's side head, which would cost $4,300! Any ideas about how serious this situation is? Can I just keep driving the car without replacing the head? Is there something I can buy to pull the fault codes and clear the "service engine soon" light (so I can tell whether its this general misfire code vs. something else when the "service engine soon" light comes on in the future)?

Thanks,
Bill

 

[TrickStang37]

did they do a leak down test? if so, i dont think those losses are that bad at all, not to where i'd bother with it yet. why would they want to replace the head? did they find out the valves were leaking? usually its the rings that do.

 

[redfiredroptop]

In my area, Autozone will loan you a code reader that can read the engine codes and clear them for no charge. You can purchase a similar reader for $100 bucks on sale.

 

[BlueOvalBill]

did they do a leak down test?

Thanks for the reply.

I don't know what type of test it was. The service report says that the leakage was through the valves, and the service writer told me over the phone that it was the exhaust valves. What questions should I ask them about what type of test they did? Thanks.

 

[TrickStang37]

if they found out it was specifically the valves, it was most likely a leak down test. those numbers seem fine, pretty good actually. the 11% is slightly bad, but not to where i would come close to doing anything about it yet. i think its fine.

 

[TrickStang37]

basically in a leak down test they use a compressor to put air in the combustion chamber through the spark plug hole at TDC. They regulate how much air goes in, and read how much air is actually staying in there. If there is a leak, they can hear the air coming out of either the intake manifold, exhaust or PCV valve. If they hear it from the intake, its the intake valve. If through the exhaust, an exhaust valve. And if through the PCV its the rings.

If they did a compression check, they basically turn the motor over, usually about 3 times, and read how much compression the cylinder is making one cylinder at a time. But with a compression check, you can't tell what the problem is specifically, not usually, but only know that you do have one. Have them do a compression check, if the compression is close enough relative to each other, you should be fine.

either way, 11% is not that bad.

 

[BlueOvalBill]

The printout from the compression test is a bar graph entitled "Relative Compression." The "y" or vertical axis is labelled "Difference" and has 0% at the top, down to 40% at the bottom. The cylinders are listed across the "x" or horizontal axis in the following order: 1, 3, 7, 2, 6, 5, 4, and 8. It then says, "Mean Cranking RPM: .170"

So, maybe they did a compression test (not a leakdown test) and are just assuming it's the valves? I'll have to call and ask.

 

[Blk03SVTCobra]

The printout from the compression test is a bar graph entitled "Relative Compression." The "y" or vertical axis is labelled "Difference" and has 0% at the top, down to 40% at the bottom. The cylinders are listed across the "x" or horizontal axis in the following order: 1, 3, 7, 2, 6, 5, 4, and 8. It then says, "Mean Cranking RPM: .170"

So, maybe they did a compression test (not a leakdown test) and are just assuming it's the valves? I'll have to call and ask.

Bill - Do you have the capability to scan that document into a JPEG? If so, I will gladly host it for you so others can see the graph you're talking about.

Let me know if you need space to host it :beer:

 

[BlueOvalBill]

Yes. I can scan it to JPEG. If you would host it for me, that would be great. Should I e-mail it to you? Thanks.

 

[BlueOvalBill]

I spoke to the mechanic who did the compression check. He said the test uses the car's computer to check compression in each cylinder while the car's running. He also said that the car would be smoking a lot and burning a lot of oil if the rings were bad. So, that's how he determined it was valves, not rings.

 

[black01mustang]

I would get a second opinion from a performance shop that can do a leak down test before spending 4300. Hell you can get sean hyland lvl2 heads for 2500 for a set.

 

[Rick James]

I would get a second opinion from a performance shop that can do a leak down test before spending 4300. Hell you can get sean hyland lvl2 heads for 2500 for a set.

+1. $4300 for a head replacement???!!! :nonono:

 

[Blk03SVTCobra]

Yes. I can scan it to JPEG. If you would host it for me, that would be great. Should I e-mail it to you? Thanks.

Soon as you scan it in, e-mail it to [email protected]

Glad to help! :beer:

 

[BlueOvalBill]

I e-mailed the JPEG.

There's a whirring/whistling sound that comes through the speakers of the stereo system when the stereo's on. The sound keeps happening for a few seconds after the stereo's shut off. And, the sound is intensified when the cooling fan is running. Is there any way that the general misfire code and the compression test results (which were processed by the car's computer) could be caused by an ignition system and/or the electical system problem that's causing the whirring/whistling noise?

 

[Blk03SVTCobra]

I e-mailed the JPEG.

And here it is:

EDIT: Resized it

 

[BlueOvalBill]

more bad news

I got a second opinion about the compression test results. The mechanic I took it to (Matt at A & G Auto Repair in Naperville or Aurora) did compression checks and leakdown tests on cylinders 5-8. I don't have all of the results (because I talked to him while I was driving). Bottom line: Cylinder 6 seems to have a problem other than rings. It might be a blown head gasket between cylinders 5 & 6. Cylinder 6 went from 70 to 80 psi when he put a few drops of oil into it. Cylinder 5 seems to have a problem with rings or the cylinder because it went from 90 to 120 psi when he put a few drops of oil into it.

At this point, I'm planning to get rid of the car. Any idea what this car is worth in this condition with 31,000 miles on it? Also, any suggestions for how I should try to get as much money out of it as is reasonably possible (i.e., how I should go about trying to sell it)?

Thanks,
Bill

 

[Tobias]

I e-mailed the JPEG.

There's a whirring/whistling sound that comes through the speakers of the stereo system when the stereo's on. The sound keeps happening for a few seconds after the stereo's shut off. And, the sound is intensified when the cooling fan is running. Is there any way that the general misfire code and the compression test results (which were processed by the car's computer) could be caused by an ignition system and/or the electical system problem that's causing the whirring/whistling noise?

YES! what are the codes? Any other diveability symptoms besides the check engine light going on and off?

 

[TrickStang37]

I got a second opinion about the compression test results. The mechanic I took it to (Matt at A & G Auto Repair in Naperville or Aurora) did compression checks and leakdown tests on cylinders 5-8. I don't have all of the results (because I talked to him while I was driving). Bottom line: Cylinder 6 seems to have a problem other than rings. It might be a blown head gasket between cylinders 5 & 6. Cylinder 6 went from 70 to 80 psi when he put a few drops of oil into it. Cylinder 5 seems to have a problem with rings or the cylinder because it went from 90 to 120 psi when he put a few drops of oil into it.

At this point, I'm planning to get rid of the car. Any idea what this car is worth in this condition with 31,000 miles on it? Also, any suggestions for how I should try to get as much money out of it as is reasonably possible (i.e., how I should go about trying to sell it)?

Thanks,
Bill

I dunno, about $12-14k im guessing.

 

[BlueOvalBill]

Any ideas about what repairs are likely to be needed? Does the engine need to be replaced? Or, if the head itself is OK and there's only damage to cylinder 5, could repairing that be significantly less expensive than replacing the motor?

 

[BlueOvalBill]

YES! what are the codes? Any other diveability symptoms besides the check engine light going on and off?

I hadn't noticed any other driveability symptoms. Just the other day, I did notice it idling roughly. The only codes I'm aware of are general misfire and misfire on cylinder 6.