Low compression in the fifth cylinder

CAROL ANN2817

MEMBER
2007 CADILLAC CTS
3.6L
V6
2WD
AUTOMATIC
90,000 MILES

Started losing power up hill and then more often got it towed to the Chevrolet dealer where it then would not start back up they said it needed a timing chain it stretched. It got towed again to another garage where it got the timing belt replaced before they changed it they said it has low compression in the fifth cylinder which was at 50 they replaced the timing chain they then said it jumped time once it got back together it still would not start? Could the belt been put together wrong or is there another problem the fifth cylinder is still at low compression at 50?

1 Reply

MHPAUTOS

MECHANIC
31,938 POSTS

There are a few tests that can be done to check and confirm low compression. First, if the valve timing was out you would have problems on all cylinders, you can do what is called a wet and dry compression test, have the engine warm and do a normal compression test on the suspect cylinder and record the readings, then add a small amount of engine oil about a table spoon to that cylinder, this will seal off the rings while you do the wet test, with the oil in the cylinder do a compression test on number five if the reading increases considerably you will have a ring problem. If the reading stays about the same the problem will be a burnt valve. With this information we can determine the next best course of action to take. Please post back the findings for further assistance.