Cat 277B issues

[Downard]

Hi all, new here. I've done a search for my current issue, but have found not answers. My 277B which has the 3044 Mitsu engine, appears to be building pressure in the coolant system. Could this be a simple plugged vent in the cap, or would you suspect that I may have a more serious problem. There is no oil in the water, or water in the oil. After shutting the engine down, you can hear the gurgling or bubbling in the system. It seems to do it before the engine builds much heat also. A simple start up from cold, and a short run of less than 5 minutes will get the result.

I have also lost the control signal to the hour meter, even though it still has power to it, it just won't count up. Looking at the schematics, it appears that there is a signal from the alternator that tells the hour meter to keep time. Is it possible that the alternator needs serviced on that matter.

Thanks for any help.

Jim

 

[02Dmax]

There should not be any "vent" in the cooling system. It should build roughly 10 lbs of pressure and the cap will release extra pressure. I always suggest to try a new cap before major repair. But it sounds like you've got a bad head gasket.

 

[Downard]

I was thinking along the same liines. Wouldn't be hard to fix, just not something I was hoping to get into.

 

[Downard]

Forgot to ask, is that fairly common with the Mistu engines, or do I have a rare bird. She's got about 2700 hrs. on it.

 

[02Dmax]

I only work on a few machines with that engine but I'm not aware that it's a common problem.

It's a pretty easily diagnosed problem though. If you're building pressure in the system and a cap doesn't fix it, it's either a bad head gasket or a cracked head.

 

[Downard]

Thanks for the input. I'm thinking it's most likely not the cap. Either the cap is working, and I'm building air into the cooling system, or the cap isn't working, and I'm still building air into the cooling system. Point being, I'm building air in the system and most likely it's combustion air entering the system via the head or head gasket. I'll probably pull the head and have it checked and if it checks out, reinstall it with new gaskets.

 

[pafarmer]

Change the radiator cap....there are no vents in a pressurized coolant system...can't help with schematics sorry...if you are building pressure in your cooling system you more than likely have a leaking head gasket or worse, the head itself....caps are cheap but it should be venting at 10 psi or so...

 

[Downard]

I just ran the machine for less than 5 minutes yesterday. It was gurgling when I shut it off, loosened the cap and it quickly blew off a lot of pressure. Looks like it's time to pull the head.

 

[02Dmax]

Is it actually blowing coolant out? Gurgling doesn't necessarily mean anything.

 

[Downard]

Well, the system is a little low now, and I can smell it. I filled the catch tank up to the normal level a while ago, and now it's almost empty, plus after taking the radiator cap off, I can see it needs topped off too.

 

[Shawnop]

I've had exactly the same happen to my 2006 277b, ended up tearing motor down and there was a crack in block where one of bolts located and crankshaft broke in two spots.