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Discussion Starter · #1 ·
Hi all:

About a year ago I inherited a 1999 6X4 diesel gator from my father-in-law. It needed a lot of work. I have almost everything working on it, but I have a cooling system problem that is blowing my mind.

1: you can't get it to fill up with antifreeze. After six months of struggling with this, I have determined that the only thing you can do it is is to raise the bed, prop the fill port up higher than the engine, and put six or 8 ounces of 50-50 in there at a time and wait for it to bleed in. After about half a day you can get it where no more antifreeze will go in. I have heard on this community that there is a plug you can pull on the gasoline models to burp them, but I have not been able to find anything on the diesel model for this.

2: so I finally get it filled up and take it for a run up the road. Eventually the engine warms up and the radiator fan comes on. I park it in the shop, turn it off, and the fan runs until the radiator is cool and then shuts off. I look at the overflow tank, and the engine has pushed about a pint of antifreeze into that tank. My understanding is that when the engine cools it should suck that coolant back in. It doesn't do it. If I drive it again, it will push more coolant into the overflow tank and not suck it back out. If I drive it enough times, topping off the coolant occasionally, the overflow tank will actually run over. I have replaced the hose, with a good worm clamp on it, and the radiator cap (original cap was totally shot) I got the radiator cap at O'Reilly's because my local John Deere guys did not have it in stock.

I park this in my shop every day. I have never seen one drop of antifreeze on the floor. I have never smelled one whiff of antifreeze while driving it. If there is a leak somewhere I would think one of these two things should happen.

I sure hope someone else has had this problem and knows how to fix it.

Best

Mike
 

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Time to check for combustion gases in the coolant.

Cracked or loose hoses will also cause the expansion system to function incorrectly.

Might also be a good time to verify the thermostat opens and close where it should (test outside of vehicle with thermometer) and ensure the water pump works as it should.

I’ve had success jacking up the appropriate side to get fill position much higher. Vacuum fill is another option.

Post back what you find.
 

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Discussion Starter · #3 ·
Hi, 200MPH:

Thanks for the reply. Last spring, after I figured out how to get the thing to fill up with coolant, I ran it up the road a mile and back. About a half mile up the road the fan came on on the radiator, so I presume my water pump is moving hot water through the radiator. I checked the engine with a laser thermometer twice on the way back, reading several places, and never saw over 190°.

I don't know how to check for combustion gases in the coolant. I presume you are thinking blown head gasket? That would be really bad news, but might explain my symptoms. When I received the thing from my father-in-law, the radiator cap was totally shot and the best I can tell there was no coolant in it, so god only knows how much it was run like that. I know the overtemperature light works, because I have seen it come on a couple of times when the coolant got too low. (Usually when sitting still idling.) Of course I turned it off immediately and got some coolant. One would hope they would stop driving it when the temperature light came on but who knows.

So I presume you are thinking a leaky head gasket could keep it from drawing coolant back from the overflow tank right? Might also explain why it is pushing so much coolant into the overflow tank?

I have had a statement from one person here that said you cannot use off brand radiator caps. I will check again at our local John Deere dealer and see if they have the cap in stock now. It might be a few days. I'll see what I can find out. If the radiator cap doesn't fix it, which I don't think it will, I'm going to be fairly depressed. I already have $1500 worth of parts and about 200 hours of work in this:"free" gator.

Again, thanks for the help

Best

Mike
 

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Hi all:

About a year ago I inherited a 1999 6X4 diesel gator from my father-in-law. It needed a lot of work. I have almost everything working on it, but I have a cooling system problem that is blowing my mind.

1: you can't get it to fill up with antifreeze. After six months of struggling with this, I have determined that the only thing you can do it is is to raise the bed, prop the fill port up higher than the engine, and put six or 8 ounces of 50-50 in there at a time and wait for it to bleed in. After about half a day you can get it where no more antifreeze will go in. I have heard on this community that there is a plug you can pull on the gasoline models to burp them, but I have not been able to find anything on the diesel model for this.

2: so I finally get it filled up and take it for a run up the road. Eventually the engine warms up and the radiator fan comes on. I park it in the shop, turn it off, and the fan runs until the radiator is cool and then shuts off. I look at the overflow tank, and the engine has pushed about a pint of antifreeze into that tank. My understanding is that when the engine cools it should suck that coolant back in. It doesn't do it. If I drive it again, it will push more coolant into the overflow tank and not suck it back out. If I drive it enough times, topping off the coolant occasionally, the overflow tank will actually run over. I have replaced the hose, with a good worm clamp on it, and the radiator cap (original cap was totally shot) I got the radiator cap at O'Reilly's because my local John Deere guys did not have it in stock.

I park this in my shop every day. I have never seen one drop of antifreeze on the floor. I have never smelled one whiff of antifreeze while driving it. If there is a leak somewhere I would think one of these two things should happen.

I sure hope someone else has had this problem and knows how to fix it.

Best

Mike
Had identical issue. Raising the motor fairly high will get rid of that last air lock. Keep burbing.
 

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They make a lot to test for combustion gases in coolant. Autozone or advance auto rents it but you have to buy the test fluid. Yes , I’m thinking head gasket could be the problem.

Extreme elevation/tilt can also help prevent air pockets as mentioned earlier.
 

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I had this problem on my 6X4 Gas, I know yours is a diesel but check this. Fill everywhere you can with radiator cap off. Then close cap. Fill recovery jug up halfway and close cap. Tube should have at least 2.5 inches of coolant covering the end. go for a test run of about 5-10 mins. Check recovery tank level and feel hoses to and from radiator to engine. Top off tank with coolant if needed. Check hoses to and from the radiator. Should be warm but not burn you hot. Repeat with a longer run. Fan should cycle and will generally run for up to 5 minutes after shutting down the engine. If it had an electric water pump, I could see why the fan would stay on. I kept opening my radiator cap to make sure water was flowing while it was running. That let air back in the system. Thx
 

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Discussion Starter · #7 ·
Hi, All:
Thanks for all the thoughts! I can get coolant in the system, with a lot of patience and fiddling. Keeping it in there is the problem. When it's in there, the fan cycles like it should and the engine temp stays around 190. During operation it pushes coolant into the expansion tank but does not suck it back in when it cools. I suspect 200MPH is correct that I have a blown head gasket. The fact that it had no coolant in it when I got it probably means it got overheated somewhere in the past, before I got it.

I'm still trying to figure out the next step. I don't know if the combustion gas test works for diesel?? I don't know if the coolant stays in there long enough to absorb any combustion byproducts, so not sure the test would tell me anything. I'll talk to the guys at oreilley's.

Again, thanks for all the input!

Mike
 

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You can always check compression or leak down test.

Even compressed air into the connection chamber can be used. Look for air bubbles in the coolant.
 

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Discussion Starter · #9 ·
Hi, 200mph:

I'm a pretty good mechanic, but I'm going to have to ask for your patience as I ask these probably stupid questions:

How do you check compression on a diesel motor? Even if I could, I think my suspected compression leak is so tiny that it wouldn't show up. I have compression gauges, but for gasoline engines.

Where you said "Even compressed air into the connection chamber can be used. Look for air bubbles in the coolant." Connection chamber? Not sure what that is. In a gasoline engine I could remove a spark plug and apply compressed air into the cylinders. Again, on a diesel engine, I'm not sure how to do that. It would be a very good test if there is some reasonable method. Remove the injectors???

Really appreciate your time. I already have 200 hours of labor and 1500 bucks of parts in this thing. One of the worst "free" gifts I have ever gotten. I'm pretty sure taking it to John Deere will result in another 2 grand for a machine that probably isn't worth 2 grand. I very badly need to figure out a way to handle this myself if at all possible. I have overhauled a couple of diesel engines in conventional tractors. This Gator is a whole different challenge. Very difficult to access the engine and components. I suspect there is a whole sub speciality of tools and expertise required. If I can determine that I'm getting combustion gasses in the water jacket, I will try my hand at replacing the head gasket, but I'd like to be pretty sure before delving into that.

Best

Mike
 

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Compression can be checked by removing the glow plug (similar to spark plug in a gas motor, but only used during preheat of the start cycle). The tread size is somewhat unique, so a random compression tester for gas may not have the appropriate fitting or pressure gauge range. Finding the correct thread adapter may be difficult through the "Loan a tool" program but worth investigating.

Another option is to check with Harbor Freight. I know some people have used one of their kits on Kubota diesel tractors.

Compressed air can be used to check for head gasket leaks into coolant, by pressurizing the combustion chamber with the piston at TDC. To do this would require the thread adapter that typically comes with a compression tester.

Another option is to leave the radiator cap off when coolant temps are low and run the engine looking for bubbles in coolant. In many cases it is necessary to put the engine under load, so it can be difficult to do safely. Have one observer off to the side with vehicle on good jack stands, while driver applies brake. Rev engine to apply load.. This will be hard on the drive belt and can even ruin it, so keep load time to a minimum.

Another option is to use a radiator pressure tester to see if the pressure decays within the coolant system. I don't like this as it can push coolant into the combustion chamber and hydraulic it. It's also possible the leak could be from a faulty hose and not the HG.

Leak down tester is another option, but finding the right thread adapter can be tricky. (great for pinpointing source of leak - valves, rings, head gasket)

Links to some of the tools: Not certain if any of these will have the necessary thread adapters... For example only.
Blown head Gasket - coolant tester
Diesel compression tester
Leak Down Tester

Hope this helps.
 

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Minimum compression pressure is approximately 400 psi and normal being 500 psi. These values are from the 855D technical manual and yours may be different, but gives an idea the difference compared to gas.


According to the tech manual, their adapter works using the injection nozzle

Automotive lighting Motor vehicle Electric motor Font Automotive exterior
 

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Font Screenshot Number Document
 

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Discussion Starter · #14 ·
OK. Doesn't look too tough to do. Thanks for looking that all up for me! Looking like Sunday before I can have a go at this. Thanks, Guy. Appreciate the help. Dreading the likely bad news.
 
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