Valtra 900 forestry tractor

[David-L]

Need some help here, I have a valtra 900 4wd tractor I use to haul my forwarding trailer and grapple around and it has what I believe to be a headgasket issue.  Constant air bubbles in the expansion tank in the cooling system. I believe the shop that did a clutch for me this spring did not purge air out of the system as it is a cab tractor with two heaters in the cab. They I believe possibly over heated it. I believe this may have started the issue as I had no problems before this with the cooling system and have owned it for some time. It has 4800 hrs on the motor which is a Sisu diesel and will tear into it for a new head gasket set which is on order. My question is, there is a 1" line from the from the bottom of the expansion tank to the water pump housing which enters the housing below the thermostat, bubbles formed in the tank I believe are coming from commpression side to the cooling jacket side of the block and coming back to the expansion tank. Does this sound right? My heat is nonexistent and temp gauge all over the place but not overheating so I believe it is not a water pump issue and have tested the thermostat in boiling water. Thanks for any thoughts on this. also no anti-freeze in the oil or vise-versa. Just when everthing is going smooth on the job stuff always happens.   Caveman

[snowstorm]

bubbles in coolant = compression in the coolant from? head gasket, cracked head, cracked liners or orings if it has liners. where are you located? some of the valmets used that motor and i know of a few in boats

[David-L]

Snowstorm, Always hope for the best but expect the worst in this game. ( cracked block). Not a fun Christmas at all. Hopefully just a head gasket. I hear these Sisu motors are pretty bombproof, I had not heard of them till I bought this Valtra. Smooth power and good lugging . Kinda the same as the Duetz 5 cylinder in my 225TJ.
Thought about it a little this a.m. waiting for the trucker and came home and took the fan belt off, took the thermostat out and put the hose throat back on making sure I could see the coolant where the thrermo lived and started her up and within a short time I was seeing bubbles. Headgasket kit on order for next week. I am in North Central Mass near Warwick. thanks for your input.

[lumberjack48]

I would try this before taking it apart.

http://www.myduraseal.com/?gclid=CLnM67bCmrQCFSWoPAodgn0AyA

[lumberjack48]

If its not building pressure in the system, no white smoke out of the exhaust, no antifreeze in the oil. and no oil in the antifreeze ??

If they didn't get all the air out of the system, the temp gauge well go up and down, and there well be bubbles in the system.
I had this problem with a 2.2 chevy, 4 cylinder.

I would run it with the rad cap louse, as the air comes out, add antifreeze.
If you can get at the hoses on the heater crack-em a little till antifreeze comes out and tighten. just thinking

[David-L]

Lumberjack48,
We are talking some serious bubbles, More than I think is allowable for trapped air. Although I will run it again tommorow without the thermostat and see if it settles out but my hopes are doubtful. I hate to run additives in motors but will look into it.

[lumberjack48]

You put it in the radiator, if nothing gained, a few $$$$ lost.

I had a 283 chevy blowing antifreeze and a white smoke cloud, Liquid glass cured it, this is supposed to be better.