6CTA m939a2 overheating issue

[dawico]

Try following the instructions in the tm?

I did but it all falls apart without access to the WPs. Are those available somewhere or buried in the TMs somewhere?

 

[dawico]

So my worthless update.

I got nothing. Refilled the reservoir with the bleed valve open. No air bled out. No pressure coming back into the reservoir either upon starting.

I did not drive it though, just let it idle for a half hour. Nothing out of the ordinary happened. Minor bubbles came out of the reservoir but that is all.

My plan now is to drain and flush the system,refill, and drive it. Then I will go from there.

This isn't the first time I had what feels like a major issue right itself. I will update after a test run.

 

[doghead]

Here's the kind of thing you can find(valuable) in the TMs.

When filling cooling system on M939A2 series vehicles, ensure
drainvalve on aftercooler is open. Failure to do so may result in
damage to equipment.

No WP needed using the TM 9-2320-272-24-1, Cooling system servicing.

Step by step procedure for filling the coolant(and flushing) is there. By the looks of it, it is not as simple as filling and hoping it works.

 

[dawico]

Here's the kind of thing you can find(valuable) in the TMs.



No WP needed using the TM 9-2320-272-24-1, Cooling system servicing.

Step by step procedure for filling the coolant(and flushing) is there. By the looks of it, it is not as simple as filling and hoping it works.

I have that TM and will check it out now. Thank you.

 

[Scott88M]

I'm pretty sure the way the shutterstat is built it can't really leak air into the system. Also for what it's worth i had a gasket leak at the thermostat housing and have torn mine apart. Mine has 2 openings for thermostats but only 1 thermostat and a rubber plug factory installed into the other spot. Oh and i had some similar issues as you and i noticed the metal gasket in the radiator cap was cracked and it wasn't the correct psi rating either. New cap from NAPA around $10 fixed my overheating issues.

 

[R Racing]

I'm pretty sure the way the shutterstat is built it can't really leak air into the system. Also for what it's worth i had a gasket leak at the thermostat housing and have torn mine apart. Mine has 2 openings for thermostats but only 1 thermostat and a rubber plug factory installed into the other spot. Oh and i had some similar issues as you and i noticed the metal gasket in the radiator cap was cracked and it wasn't the correct psi rating either. New cap from NAPA around $10 fixed my overheating issues.

We had a member on here a few weeks ago that had that exact problem. His Shutter Stat was presureizing his coolant system and forcing coolant out of his engine. So it is possible.

 

[Swamp Donkey]

I'm pretty sure the way the shutterstat is built it can't really leak air into the system. Also for what it's worth i had a gasket leak at the thermostat housing and have torn mine apart. Mine has 2 openings for thermostats but only 1 thermostat and a rubber plug factory installed into the other spot. Oh and i had some similar issues as you and i noticed the metal gasket in the radiator cap was cracked and it wasn't the correct psi rating either. New cap from NAPA around $10 fixed my overheating issues.

There is an O-ring under the jam nut on the stem of the thermal capsule where it screws into the shutterstat housing. If that O-ring leaks, it will let pressurized air into the coolant system.

 

[Suprman]

When you flush it out you need to drain it and then take off the upper radiator hose and stick a water hose in there to really get all the rust and gunk out. I have heard stories off all kinds of yuck and gunk coming out.

 

[dawico]

When you flush it out you need to drain it and then take off the upper radiator hose and stick a water hose in there to really get all the rust and gunk out. I have heard stories off all kinds of yuck and gunk coming out.

Yup. I had rust colored water for an hour using the hose. I disconnected everything I could and flushed from every direction possible. It was pretty bad with rust. No big chunks of anything though.

I am going to run it again tomorrow and flush it again and try to get everything out possible. Then I will add coolant and see how it goes with the original issue. Didn't see any sign of it today.

 

[dawico]

On a side note, the drain on the radiator is about worthless. Taking the smaller thermostat bypass hose off by the oil cooler really let the water flow.

 

[Scott88M]

I knew it could vent out the back leaking into the coolant is a new one on me but i can visualize how its possible now

 

[leo4x4]

some m923a2 have 3 thermostats 2 where the alternator is and 1 at the top where the hose connects, mine had a similar issue i replaced the thermostats, i only installed the 2 next to the alternator
mu truck runs at 210 on hot California days .

 

[dawico]

A little more for an update.

Flushed the system and got a ton of rust out. Refilled it with just water and gave it a little test run. Temperature still rose right up to 240°. Pulled the thermostat (just one big one on my truck) and it opened right up in a pot of boiling water.

So now I move on to other suspects.

As near as I can tell the original boiling over problem while cold may have been some kind of vapor lock. The truck has not done that again.

 

[doghead]

Are you using an IR gun to confirm the temp?

 

[Suprman]

Most auto shops have a test kit for combustion in the coolant. Chances are you have some type of head gasket or sleeve failure.

 

[Csm Davis]

Doghead hit the nail on the head for anyone having a temperature problem on these trucks please grab a IR gun and check out the temperature of the truck the sending units tend to fail high which is a good thing but can spook you a little bit when it happens.

 

[Csm Davis]

Also as mentioned above flush, flush, flush. If y'all saw the crud come out of the good looking trucks we have disassembled everyone would be flushing there trucks, I have even thought about flushing my 2012 rebuild.

 

[dawico]

Also as mentioned above flush, flush, flush. If y'all saw the crud come out of the good looking trucks we have disassembled everyone would be flushing there trucks, I have even thought about flushing my 2012 rebuild.

I was talking to the auto parts guy and he called a buddy that worked on these for years in the military. We were talking coolant, SCAs, that type of thing. His buddy started with "If we put in more than just water, add whatever you want. It doesn't really matter." Not surprising after I saw all the rust.

 

[dawico]

Are you using an IR gun to confirm the temp?

Not yet. On my list. I am sure it is getting hot though.

 

[Csm Davis]

Not yet. On my list. I am sure it is getting hot though.

Yes but what we are saying is don't trust the gage and also you can point it at different areas to determine flow