Bad head gasket after overheat?

[bradfr]

So I recently had a stud gouge my heat exchanger while riding and let all of the coolant out. Before I had realized this happened the engine temp light came on. Once the light came on I pulled over and checked things out. I did not ride very long with that light on but the snowmobile did shut off by itself when I let off the throttle. From there I limped back to the trailer shutting down when the temp light would come on. Since then I have had the exchanger welded and re filled the coolant system. The last time I rode(after the weld/fix) the engine temp light would come on and off kind of randomly and the system would overheat and puke all of the coolant out. I did notice the coolant that I refilled with was no longer green and possibly oily. I have done a compression test which looks good at 200/cyl and I am now attempting a leak down test. Are you able to leak down test these engines or is there a decompression valve somewhere that I might be missing? When I bring the cylinders to TDC on the compression stroke and leak down test it sounds like the air escapes to the bottom part of the motor. Am I doing something wrong or should I tear the head off?

 

[SSX600]

Pull a vacuum on the coolant system and see if it holds that should tell you if there is something wrong.

 

[bradfr]

Bump for any other thoughts?

 

[LSXM3]

I work in the automotive world and anytime a car overheats we install a new thermostat, radiator cap and temp sensor as all three can become damaged or out of range due to the extreme heat they saw.

I would start with all three of those and go from there as they all could easily damaged from an over heat condition!

Good luck

 

[canoehead]

I agree with ssx600 pull a vacuum or pressure up the cooling system that'll tell you if it's the head ga$ket.

 

[bradfr]

Ok, I will see what i can do about pulling vacuum on the cooling system. I will also check the thermostat and sensor and cap. Tonight I put it all back together, drained any left over water/coolant and refilled with 60/40 coolant to water. I ran it for 5 mins with the cap off to bleed the air out and it didnt really require any more coolant. I have been letting it idle in the garage on a stand for about 35 mins now and it hasn't over heated yet. I am wondering if things will be different when it is under load.

 

[canoehead]

No cap means your system won't pressure up. Amny white smoke from the exhaust?

 

[bradfr]

No white smoke in exhaust. I let it idle last night for over 40 mins and it was about 32F out. It was warm but no temp light. I am going to buy a laser temp light today and let it run again. I was also thinking to drain the coolant again and have a peak at the water pump.

 

[canoehead]

Normally on a overheat on most engines you'll warp the head then the head gasket will go after some time. I sure hope you get to the bottom of this and let us know your findings.

 

[bradfr]

Picture of head

Well after all of my checks I decided to pull the head. Is the brown on the center cylinder signs of blow by or a problem? That is the only thing that looks abnormal to me.

 

[Supa Dexta]

Whoa.. What were your checks?

Hopefully there were several, and they would point you in the right direction. At this point you dove head first into it with your eyes closed it sounds like.

Blow by is more a term for loose rings where you are losing cylinder pressure into the crank case.

But in this case it *looks* like you were losing into the center water jackets.

Any compression in that cyl? If you were pushing coolant, (from the looks of that it would be quickly) and it looked dirty, then yeah - you've found your problem.. or the start of them anyways.

 

[bradfr]

My checks were compression on each cylinder(200 psi each), made sure radiator fan was coming on at right temp, removed thermostat and tested in hot water, leak down test(no cylinders would hold pressure at TDC on compression stroke) removal of water pump for inspection.

I am far from diving head first with my eyes closed. I tested everything in the cooling system prior to head removal.

The head is warped in that area about .0035". It is within spec but i might resurface it anyway. All cylinders had 200 psi of compression before tear down.

There were also signs of oil in the coolant when all of this happened. The only thing that I did not verify was the oil cooler. Im not sure if I could pressure test that somehow or not.

 

[Supa Dexta]

I can't see there being any leak then with 200 psi

 

[canoehead]

I know someome who's been having the same problem. Compression was good and no warped head but he has a cracked water jacket from overtemps. Are you going to mill the head? Good luck.

 

[bholmlate]

Hate to bring up a semi obvious thing at this point but did you make sure that all the air was bled out of the cooling system? You could have had air pockets in the system causeing overheating. If you where loosing coolant through combustion you would be able to smelll and see it coming out the exhaust in the form of steam. If you are getting that type of compression it doesnt sound like there is a leak in that area. The oily film is a little concerning though. Have you looked at the oil to see if there is any water getting into it? The cracked water jacket is an interesting one. Hey canoehead how did your friend determine he had a crack there?
I just thought of something else Did you make sure after they welded the cooler that there was not a huge restriction in the area of the weld.
Just throwing out some ideas for you. hope you find and are able to fix things up good luck.