Low compression after overheat

[Mooseman]

I just bought a 2007 Phazer GT with 8500Km for a pretty good price but it has a problem. It was brought in to the dealer with low compression in a cylinder after an overheat (circumstances unknown). He brought a replacement head and had it done by them saying that was the problem. So the dealer swaps the head, same problem. Customer refuses to pay for the work so he gives the sled to the dealer (with papers ). So he's selling it just to recoup his labour.

Here are my thoughts on what could be causing the low compression in the one cylinder:
- warped block deck
- replacement head also warped
- dealer botched the job (doubt it)
- damaged cylinder or block

So this will be a summer project sled for my youngest son so no rush. It also has really bad slop in the steering, it moves 5-6 inches (already know how to fix that). I just wanted to get some ideas as to what could be causing this low compression. We are picking it up this weekend and may do a quick look see if sledding conditions don't improve and have nothing better to do.

Oh, it's also ugly as sin... dark blue and off-white plastics, a brown seat, yellow springs, bronze a-arms and ugly aftermarket add-on mirrors.

 

[Ridndirty]

Collapsed piston, or rings. The dealership should have done a leak down test on it before they went to all the work of changing the head.

 

[marpolsdofer]

I agree with you that it could also have a warped deck well or the cylinder an piston is warped. Is there any blow by? The over heating could have cooked the oil and deposits on rings. If the ringer are to built of with carbon they could be stuck and then blowing by.

Leak down test would be able to be able to find the problem.

I just rebuild my Toyota engine around 6 months ago. engine was burning oil (very slow rate) and low compression. The problem the oil filter is to close to the pipe. Oil would get hot and then evenly cook on the rings. The rings become stuck and would bot even rotate or expand past the piton to contact the oil film and the wall. It was also later discovered the they used a inferior oil control ring.

 

[gordo]

Me thinks that is a FX and it's purdy...

 

[canoehead]

Looks like a monkeys lunch!!

 

[biffdotorg]

Me thinks that is a FX and it's purdy...

Yup, the Phazer FX in '07 was available in Blue and Khaki. They even had matching "urban camo" jackets and pants to match the Khaki pattern that year. It will grow on you, but I ordered the blue for a reason!

Good luck, what a great project!

 

[RIGIDONE]

I just bought a 2007 Phazer GT with 8500Km for a pretty good price but it has a problem. It was brought in to the dealer with low compression in a cylinder after an overheat (circumstances unknown). He brought a replacement head and had it done by them saying that was the problem. So the dealer swaps the head, same problem. Customer refuses to pay for the work so he gives the sled to the dealer (with papers ). So he's selling it just to recoup his labour.

Here are my thoughts on what could be causing the low compression in the one cylinder:
- warped block deck
- replacement head also warped
- dealer botched the job (doubt it)
- damaged cylinder or block

So this will be a summer project sled for my youngest son so no rush. It also has really bad slop in the steering, it moves 5-6 inches (already know how to fix that). I just wanted to get some ideas as to what could be causing this low compression. We are picking it up this weekend and may do a quick look see if sledding conditions don't improve and have nothing better to do.

Oh, it's also ugly as sin... dark blue and off-white plastics, a brown seat, yellow springs, bronze a-arms and ugly aftermarket add-on mirrors.

Thats the color mine was when i got it, i only have the copper a arms left to get changed to my liking..

 

[Mooseman]

Compression tests I can do, leakdown is something else. First I'll have to get a tester and learn how to use it. How would you know where it's leaking? From the sound of the air leaking out?

My son's already talking carbon fiber

 

[Ridndirty]

Yup. Get piston at top dead ctr. And put the air to it thru the spark plug hole. Listen at the throttle bodies, exhaust and crankcase vent to find out where it's going.

 

[marpolsdofer]

You can make you own one if you have stuff laying around I had to when I was rebuilding my engine becaues the other one took a dump (I dont know why it just was not working and I did not care to fix it it was old).

Its simple warm the engine, take out one plug, get piston TDC. Lube the o-ring on the tester and tread it to the hole, then hook up air supply and supply the air.
Instructions will tell you how to zero it out and what psi is needed.

Respectable leakage numbers would be anywhere from 8 to 12 percent with a variation between cylinders of 4 to 5 percent, but it's possible the variation could be as high as 10 percent.


If you have a auto stethoscope you can hear the air leaking or you can use soapy water and look for bubbles.
Leak downs also give you more then leak indicators other then in the cylinder. Such as the head gasket with cylinder to cylinder leaks, oil to cylinder leaks, coolant to cylinder leaks.

 

[Mooseman]

Definitely good info on things to look for. I'm just wondering if I should just do a full rebuild since I know nothing of the history of this engine and I wouldn't want to have to tear into it again if I just do a partial (head or rings) and something else goes. I just want it to be reliable and not have it blow like a Doo.

Looks like I'll have the time since the trails are now closed and there is no snow in the near future.

 

[Ridndirty]

Rebuild it quick, and bring it out here to break it in! I was out running the groomer last week, and there is well over 2 feet in the bush, and we got another 4 to 6 inches this week.

 

[marpolsdofer]

I would not worry much about the bottom end unless you suspect any issues.
If you dont have a micrometer take it to a machine shop and they will mic it to see if the cylinder is round and true same with the pistons, head, and deck. That is if you dont have tools to do such. Are the heads heads sealed by orings? (or something of the shape of the head and not really a flat gasket). Then you wont need to worry about it the RA.
If its just rings- hone the cylinder and re ring it. If its scored then you need over sizing them. Some times depending on how bad it is they can just go a hair and keep in stock size. It depends of the cylinder conditions or out of roundness and the piston out of round scuffing, holes, ext.
The book should be able to tell you measurements and if they are in spec of not.

 

[Mooseman]

Thanks Marshall. I know these engines are bullet proof so I'm not too worried. Was just thinking out loud. I did check the manual and it doesn't look too bad of a job to do just the head. Could also be a bad or carboned valve too in that "new" head. I can check them using solvent in the intake and exhaust ports.

Going to pick it up today. Knowing my boys, they'll want to start tearing into it right away. Trails are closed so we do have the time :'(