Green Yanmar Problem

[R Barger]

One of my John Deere 850 tractor has a problem I can't figure out. For the last year or so the coolant won't return to the engine after cool down.
Here is the things I have tried
Checked the hose and the recovery tank for leaks.
Replaced the radiator cap.
Flushed the system with radiator flush.
Replaced the thermostat.
Checked for combustion gas in radiator. [none]

The tractor does not over heat.
It runs perfect.
No smoke or steam from exhaust.
The tractor has slight pressure in the system even if left for days.
I have purchased a head gasket and don't mind to replace it but I would hate to do that and still have the problem.
Tomorrow I am going to back flush the the radiator.


ANY IDEAS?

 

[dodge man]

I’m confused, what’s the problem. Coolant goes into the overflow tank but won’t go back in the radiator later? Have you checked the radiator after this happens and it’s low?

 

[ponytug]

What do you mean by slight pressure after a few days? Is it possible that your hoses are getting soft and ballooning up a bit?

Are you sure that the radiator cap is the correct one? Have you had tested it for pressure/vacuum function?

All the best,

Peter

 

[R Barger]

I’m confused, what’s the problem. Coolant goes into the overflow tank but won’t go back in the radiator later? Have you checked the radiator after this happens and it’s low?

When the coolant expands it goes to the overflow tank and should be sucked back into the radiator. After a few times of running the over tank overfills if I don't take it out and return it to the radiator.

 

[R Barger]

What do you mean by slight pressure after a few days? Is it possible that your hoses are getting soft and ballooning up a bit?

Are you sure that the radiator cap is the correct one? Have you had tested it for pressure/vacuum function?

All the best,

Peter

The slight pressure I am not concerned about. The fact that it hold that pressure shows there is no leak. I have not had it tested. It is a 13lb recommended for the John Deere 850. The old cap had the same problem. I have owned this tractor for several years. 800hrs. I use it to mow about 3 acres weekly. As long as I return the coolant every couple of mowings no problem. I just decided I would try to get to the bottom of the problem before mowing season.

 

[Racer4]

That coolant flowing from the rad into the catch tank is being displaced by air. That air is coming from somewhere, most likely combustion gases. But you said you had the coolant tested for combustion gases, right?

A leakdown test could confirm this.

 

[R Barger]

That coolant flowing from the rad into the catch tank is being displaced by air. That air is coming from somewhere, most likely combustion gases. But you said you had the coolant tested for combustion gases, right?

A leakdown test could confirm this.

No I have not had the coolant tested. That was just based on my visual inspection of no bubbles in coolant when running and no funny looking gases or smoke on start up or running. You may be right that's why I have bought the head gasket. Just didn't want to do that if there was something I was missing.

 

[Racer4]

I think you can get test kits from an auto parts store that can tell you if there are combustion gases in your coolant. I would do that before tearing into the engine.

 

[bmaverick]

No I have not had the coolant tested. That was just based on my visual inspection of no bubbles in coolant when running and no funny looking gases or smoke on start up or running. You may be right that's why I have bought the head gasket. Just didn't want to do that if there was something I was missing.

Replace the radiator cap. The vent is plugged or the deflection disc will not spring back.

 

[KennyG]

Make sure the overflow vent is clear. If it isn't, air can't come back in and let the coolant return. I'm a little confused by the statement that there is pressure on the system after shutting down. If there is pressure in the cooling system after it cools off, that would keep the coolant from returning. It should go negative after shut down.

 

[tacticalturnip]

Replace the radiator cap. The vent is plugged or the deflection disc will not spring back.

You're a treasure in this community- coming here with simple solutions and the knowledge to back it up!

 

[R Barger]

Replace the radiator cap. The vent is plugged or the deflection disc will not spring back.

I have replaced the radiator cap with a new one and also tried a couple of others including a vented 15lb one.

 

[R Barger]

Make sure the overflow vent is clear. If it isn't, air can't come back in and let the coolant return. I'm a little confused by the statement that there is pressure on the system after shutting down. If there is pressure in the cooling system after it cools off, that would keep the coolant from returning. It should go negative after shut down.

The overflow is clear. That is the first thing I checked. I can't check it 2 days after running it and there will be slight pressure in the system. That's what is why I thought the system does not have a leak.

 

[careyo63]

Remaining pressure days later sounds like a dirty clogged up radiator. Air pressure pockets is what I call it. Running should be around 13-15 PSI.. A big chain Auto parts store will rent or lend a test kit to check it.

 

[R Barger]

Remaining pressure days later sounds like a dirty clogged up radiator. Air pressure pockets is what I call it. Running should be around 13-15 PSI.. A big chain Auto parts store will rent or lend a test kit to check it.

My thought is maybe part of the radiator is clogged causing a little more than normal pressure when running at 2000 rpm for a length of time. Coolant not leaving the bottom as fast as the pump is putting it in. I am going to back flush the radiator today if that don't change things I'm going to go ahead with the head gasket replacement.

 

[ponytug]

My thought is maybe part of the radiator is clogged causing a little more than normal pressure when running at 2000 rpm for a length of time. Coolant not leaving the bottom as fast as the pump is putting it in. I am going to back flush the radiator today if that don't change things I'm going to go ahead with the head gasket replacement.

Have you tried looking in with a bright light or borescope to see if you see signs of gunk or corrosion?

All the best,

Peter

 

[KWentling]

Kind of a long shot here but I have seen the inner lining of hoses come loose and act like a check valve. You might check the hose between the expansion tank and the radiator neck.

 

[R Barger]

Kind of a long shot here but I have seen the inner lining of hoses come loose and act like a check valve. You might check the hose between the expansion tank and the radiator neck.

The hose is a single ply hose with no problems.

Today I removed the thermostat flushed the engine and back flushed the radiator. Everything is very clean. At 2000 rpm with the cap off the the water passes through the radiator with no restrictions. The thing that surprised me was I put the radiator cap on and rode the tractor at 2000 rpm for 15 min. and it put no water in the expansion tank. The was cool enough that I could put my bare hand on it. Every time I decide to do the head gasket, I start having second thoughts.

 

[ponytug]

The hose is a single ply hose with no problems.

Today I removed the thermostat flushed the engine and back flushed the radiator. Everything is very clean. At 2000 rpm with the cap off the the water passes through the radiator with no restrictions. The thing that surprised me was I put the radiator cap on and rode the tractor at 2000 rpm for 15 min. and it put no water in the expansion tank. The was cool enough that I could put my bare hand on it. Every time I decide to do the head gasket, I start having second thoughts.

Diesels are much more efficient than gasoline engines, as they are fuel limited. A fair amount of the non-work heat losses are passed through the exhaust due to lean mixtures burnt in a diesel engine.

That said, my apologies, I am still trying to understand your problem. The engine isn't overheating, it runs, and it leaves some coolant in the reservoir. That sounds like normal operation from this armchair. What am I missing?

All the best,

Peter

 

[kennyd]

LOL, here's what I thought from the thread title: