Cooling System Internal Leak Questions

[Blue Dave]

Hi Guys,

I had an issue where my rear heat exchanger had a cracked weld that resulted in coolant loss and the subsequent overheating of the motor. I limped it along for a while at slow speed before deciding to tow it back to the trailer.

The weld has been fixed and there is no longer an external coolant leak. Now I am experiencing an internal leak obviously caused by driving the sled too far without coolant.

I am going to do a compression check next on all three cylinders to see what I find. I am assuming that I will be dealing with a head gasket failure or warped head? Any suggestions on how to proceed? I consider myself a good mechanic so I am hoping that this repair will be within my abilities. What is the worst case scenario here that I should be prepared for?

 

[Turboflash]

If head gasket is out (IMO likely), compression test may not tell you much if anything.
Check your oil level. Is it over-full? As you say you have an "internal leak" that to me means coolant in the oil. Obviously do not run engine until it's fixed. If there's enough coolant in oil, it could take out all bearings!
Assuming head gasket, head needs to come off, must be checked for flatness. Block needs to checked for flatness as well.
May as well install head studs while you're at it. Chech all valves. Check shim/re-shim if needed.
JM2C

 

[Blue Dave]

Thanks!

The sled is losing coolant somewhere and there are no external leaks. I have added a significant amount of additional coolant after the initial re-fill thinking that I was displacing air when I burped the system. The oil level is normal and looks clean & undiluted. Therefore I am thinking that it must be burning it in the combustion chamber?

I do not see any other possibility. Thanks in advance to anyone who has any tips or advice for me before I start taking the head off.

 

[74Nitro]

Most likely pushing it out the coolant overflow as combustion pressure is much greater than cooling system pressure.
This same thing happened to an Apex I service many years ago. It was driven a mile or two with no coolant. It would only push coolant out the overflow every few miles of driving. Luckily a new head gasket fixed it.
On the other hand I've seen engines ruined because they've been driven too long without coolant.
I agree with Turboflash that the head and block surfaces need to be checked for straight.

 

[NYTurbo]

Is your over flow bottle full ?
If not pull oil drain on motor and see if coolant trace come out.

If it’s burning anti freeze there would be a lot of white smoke

 

[Blue Dave]

Hi Guys,

I saw another post about how difficult it can be to bleed all the air out the Sidewinder cooling system and thought I would try bleeding air one more time to be 100% certain that this was not an airlock issue. I learned in the other post to bleed through the turbo housing bunghole which I had not done before.

I am happy to report that what I thought was an internal leak was actually a surprising amount of air still trapped in the system being displaced by coolant. It took a few heat / cool cycles and lots of bleeding and re-filling at the bunghole to get all of the trapped air out. I then tested it with a 30 mille trail ride on poor snow with warm air temps and observed normal coolant temps.

Thanks again guys. I learned something from the TY community again and was able to fix the issue myself which saved the rest of my riding season.

 

[Turboflash]

Glad you got it fixed. TY is the best!