[JohnBee]

I just had my the compression tested on my 2018 Cruze and was informed that the results were between 105 and 110 PSI across the board.

Needless to say, I was in disbelief, as the car had a major engine overhaul no less than 6 months ago, and so the mechanic was kind enough to come to my house and double check the results. He did this by removing one of the spark plugs, connecting a gauge, and starting the engine, which sputtered and ran terribly, but idled nonetheless, so that he could capture a max reading.

This was performed on two cylinders, that showed about 10% between them.

With that said and after reading several threads, I've been seeing numerous comments referencing specific conditions to get a proper reading. And so my question is, could the low compression be due to improper setup? or was the used method used sufficient in getting an accurate reading?

Thanks in advance for any help with this.

 

[Barry Allen]

Is the car starting and running fine? If the answer is yes, why would you need anything rebuilt? Just keep driving it.

 

[JLL]

The technician had you start the engine for a compression test???

Normally compression tests are done with all the spark plugs removed and with the fuel system disabled.

 

[snowwy66]

Engine warm. Wide open throttle. All plugs removed. Fuel pump disabled.

Add some oil to see if compression comes up. That would indicate piston rings.

Minimum compression needed to run is 80.
I have no idea on the spec with these motors for top compression.

 

[15cruzediesel]

That seems low.

I'd expect over 130 dry.

At least the readings are all close.

All this is assuming the guage used is calibrated and accurate.

I'd do aleak down test.

Tells you way more than just a compression test.

I'd find another mechanic. His methods are questionable at best.

Ultimately it would be nice to know why you got a compression test?


. And so my question is, could the low compression be due to improper setup? Yes. We don't know what a "major" overhaul consists of. Many things could have been not correctly done.

or was the used method used sufficient in getting an accurate reading? See questionable mechanic comment.

 

[JohnBee]

Hello everyone, and thanks for all the suggestions and help!
With respect to the questions provided in the comments, here are the respective answers;

1. The car blew a piston about 1500km ago, and was rebuilt by the dealer under warranty
2. The car did not run properly since the rebuild, as it was idling rough and at times sounding like it would stall
3. The dealer could not find any fault with the car, citing no codes and /or capacity to identify a problem

Following this, I have done a few oil changes since the rebuild and the mechanic doing the oil suggested we do a compression test to establish a troubleshooting starting point.

PS. on the rebuild notes, it would seem that the dealer rebuilt cyl #1, and reported that the compression of the remaining cylinders was 250psi - whereas now(1500 km later), those same cylinders(2,3,4) appear to be reading 105-110psi

 

[Barry Allen]

The TSB for cracked pistons says to replace all four. They owe you a rebuild of all four pistons.

 

[JohnBee]

Hi, could you explain more on the TSB and warranty work. I'd love to present a case for the vehicles current performance and low compression, though I'm not confident on the diagnosis, or the dealers obligation in matters.

Thanks again for your ongoing help and suggestions with this.

 

[Barry Allen]

Hi, could you explain more on the TSB and warranty work.

Here is the TSB: https://static.nhtsa.gov/odi/tsbs/2019/MC-10163888-9999.pdf

They are to do some diagnosis of the vehicle and if the cylinder walls of the block aren't damaged all four pistons are to be replaced. Note in the parts on page two of the TSB that 4 piston kits are called for, so the dealership shouldn't have replaced just a single piston.

Time to take the car to a different dealership and have them do the job correctly.

 

[Barry Allen]

1. The car blew a piston about 1500km ago, and was rebuilt by the dealer under warranty
2. The car did not run properly since the rebuild, as it was idling rough and at times sounding like it would stall
3. The dealer could not find any fault with the car, citing no codes and /or capacity to identify a problem

This is so funny as to be unbelievable. They rebuilt the engine (apparently just one cylinder with a new piston), the car didn't run properly after the rebuild, and THEY COULDN'T FIND FAULT WITH THE CAR.

Um, isn't the fault with the car the fact that isn't not running right after they rebuilt it?

 

[JohnBee]

This is so funny as to be unbelievable. They rebuilt the engine (apparently just one cylinder with a new piston), the car didn't run properly after the rebuild, and THEY COULDN'T FIND FAULT WITH THE CAR.

Um, isn't the fault with the car the fact that isn't not running right after they rebuilt it?

The conversation went as follows;

1. Is there an engine light warning? no
2. Is there a fault code? no

There is therefore nothing wrong, or in need of fixing with the car.

Following this, my follow-up discussion went as follows;

3. Our mechanic drove the car and couldn't find anything wrong with the performance
4. You say the car idles rough, but we found it to be normal

There is therefore nothing wrong, or in need of fixing with the car.

The last time I brought the car over, they put-in an engine treatment and charged me 200 dollars. I then called them back to report it was still idling rough, like it was going to stall, the service person told me I must be doing something wrong.

 

[Barry Allen]

Time to find a different dealership and press your case that the prior repair (cracked/blown piston) wasn't done properly. They replaced one instead of all four, as should have been done.

This is going to be a tough argument because they aren't going to want to admit that the prior repair was done improperly. It's an expensive cost to them to have a mechanic do the engine rebuild again, so they're going to try to say it's fine and nothing needs to be done.

 

[Valpo Cruze]

Escalate to Chevrolet people above the dealer

 

[Barry Allen]

Escalate to Chevrolet people above the dealer

Yes, this, and best of luck. If they find out the prior repair wasn’t done properly (replace ALL pistons), they will be uncomfortable about needing to do another engine rebuild job (replace 3 or 4 pistons) if you can’t show anything wrong with the car that has diagnostic codes triggering a CEL.