RTV 500 overheating

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Franzh

New member
We just purchased a used 2009 RTV 500 with just over 1000 hrs at an auction. We werent able to perform a thorough inspection of the RTV but we were able to start it and move it back and forth. When we got home and started using it, it overheated very quickly, blowing coolant from the overflow bottle along with a constant high volume of steam. I added about a cup of coolant, and verified that the cooling fan is operating. It starts and runs perfectly.

As a retired ASE Master automotive technician and college level instructor teaching automotive technology, my initial impression is a blown head gasket or cracked cylinder head. I plan on doing a more complete diagnostic test in a couple of days when the weather clears up: pressurizing the cylinders with air and see if bubbles come out of the coolant filler neck.

This weekend I have spent more time than I care to admit searching the various fora to see if this is a chronic problem or do I have an isolated case.

Does anyone have any experience with this engine or problem?
 
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simple fix. wash your radiator out good with low pressure water or air.my 500 does the same thing the screen lets stuff by it
 
Thanks, thats the first thing I will check. What worries me the most is how fast it begins blowing coolant out of the bottle. The temp gauge never got over half way and it was blowing a steam geyser about 2 feet out from the right side of the ATV.
 
I did a very thorough inspection today and found that the plastic radiator cap neck, mounted in the upper radiator hose, was severely deteriorated, to the point where the radiator cap could not seal properly. A new neck is a couple of days away when I will continue the diagnostic process.
 
You are on the right track. We just had the same experience with a 2009 RTV 500 that our soil and water conservation district owns. We run this machine down a lot of grassed waterway and open ditches. The radiator gets plugged up all the time with soybean fuzz and weed seeds. We will blow it our regularly. I had it home in early summer to power wash it and clean it up for a field day. I guess I didn't get all of the water out of the radiator because by the next week it was overheating quickly every time we used it. I blew it out with air again but it would never help. Fan ran all the time and temp gauge showed hot. Now that was the cause we believe but what happened is that the plastic piece that the radiator cap seals against got hot and out of shape. This would not let the radiator cap seat. Steamed all the time. Put new thermostat in and no difference. The head gasket started leaking and the head was cracked on the low pressure side along the cast seam on the outside of one of the cylinders. Put new head gasket on and new plastic piece for cap and cleaned both sides of the radiator out with water and let it dry for a week. Has run ok since. New head was 1200 bucks so we used it again.
 
The filler neck is seriously eroded and warped. If it overheated, it was bad enough to warp the plastic. In 43 years of automotive work, I have never seen one this bad. Also, the inside of the neck is coated in what looks like cement or calcium, about 1/16" thick, like someone poured something in it.

Hopefully the radiator is not in the same condition as the filler neck.
 
I installed the new filler neck and some Prestone Super Flush (about 1/3 of the bottle) and clean water. I then ran it for about 1 hour and operated it hard. The temperature cycled up and down, from just above the cold mark to just under the hot mark, and the cooling fan came on periodically. I then removed the spark plugs and let it sit overnight.
The next day, I spun the engine over and no coolant came out of the plug holes (yeah!). I flushed the cooling system out again and was surprised by how little actually came out of the radiator. A clean water refill and drove it again for about an hour.
It spits a little coolant out of the overflow when I hit the throttle but otherwise, it ran smooth and stable, with the same temperature swings. I am going to run it through the paces this weekend, and if it behaves, I am going to give it a 95% passing score. Not 100% convinced but pretty close.
 
That is where the remaining 5% of doubt is. The amount of scale that was inside the filler neck is hard to explain, easily enough to reduce the radiator's capacity by 50%, if it made its way down there. The radiator is not that easy to access so I'm not going to pull it just for grins. I'm willing to pull the head if that's what it takes but I dont want to pull it just to inspect it.

Thanks.
 
What is troubleing is that it blows coolant out under load. That sounds like a head gasket. You may try to re torque the head and see if that stops the leak. If that is what is going on, after time it can eat a chanel in that area, witch may mean a block or head or both . VERY EXRENSIVE.
 
oldhat said:
What is troubleing is that it blows coolant out under load. That sounds like a head gasket. You may try to re torque the head and see if that stops the leak. If that is what is going on, after time it can eat a chanel in that area, witch may mean a block or head or both . VERY EXRENSIVE.
Click to expand...


.......... and I agree !!!!
 
Well, the 5% got the better of me late Saturday afternoon and I pulled the head. This engine has two free-standing cylinders, also called a wet-deck block. The head gasket is made from two metal shims with what appears to be a sealing coating and a raised ring that seals the cylinder to the head. At several of the coolant passages, there appear to be some erosion in the metal gasket which then connect into the combustion and oil drain back areas, and I did find a very little coolant in the head, something the dipstick did not show. There was a little emulsification in the top end.

Today, I clean everything up and pull the valves for a thorough combustion chamber inspection and hopefully no cracks. I'll try and find a good machine shop to true the head, or I can do it myself with a flat table and 220 grit wet and dry sand paper.

Thanks for the encouragement, folks, I wasnt totally convinced I had repaired the problem with the filler cap.

Franz
 
Franzh said:
Well, the 5% got the better of me late Saturday afternoon and I pulled the head. This engine has two free-standing cylinders, also called a wet-deck block. The head gasket is made from two metal shims with what appears to be a sealing coating and a raised ring that seals the cylinder to the head. At several of the coolant passages, there appear to be some erosion in the metal gasket which then connect into the combustion and oil drain back areas, and I did find a very little coolant in the head, something the dipstick did not show. There was a little emulsification in the top end.

Today, I clean everything up and pull the valves for a thorough combustion chamber inspection and hopefully no cracks. I'll try and find a good machine shop to true the head, or I can do it myself with a flat table and 220 grit wet and dry sand paper.

Thanks for the encouragement, folks, I wasnt totally convinced I had repaired the problem with the filler cap.

Franz
Click to expand...

My suggestion would be. Let a professional tune the head. He has the proper equipment and can test. Cost should not be that much.

But that is just my opinion, worth maybe 5 cents :whistling:

........... jamie
 

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I am glad you found the problem. If you had not found it now it would have been a continued problem. You should come away with a great machine.
 
The head is at the machine shop now. I still dont know the root cause of the blown head gasket. I dont know if the engine overheated and then blew the gasket, or if the gasket blew first then overheated. Knowing Kubota's rock solid reputation throws a wrench in the works, as no one I have talked to in the area has had a head gasket failure. Either way, the gasket must be repaired before I can do any further diagnostics. When I go back together, a new thermostat is going in too. My wife is eager to get it in service, my chore list is growing and a lot of it is based on moving rocks and tree stumps. Gee, how long does it take to do the head?
 
Our was a head gasket also. I believe that the overheating caused the head gasket to fail. If the radiator was dirty that got hot and messed up the neck. Then each time it got hot it messed up the gasket. What you are describing is the exact thing that happened to the district. We used the head and just put a new gasket on and thermostat. That's all and been working good.

You have to keep that radiator on that machine clean. The fan is not big enough and the fins are so small nothing will pass threw. If the gauge is over half on the temperature than radiator needs cleaned. This is my experience.
 
Follow-up:
I ordered the top end gasket set and had the head professionally shaved. It took almost .020" to get it flat. There are signs of serious overheating but there doesnt appear to be any internal problems with the pistons or rings (I didnt remove them but the cylinder walls are almost pristine). Several things to mention:

Head bolt torque on this engine feels very low, factory 18-23 lb ft, I set it at 25 and still feel it is too low, but that is what the book calls for.
The valve clearance was WAY off. Book clearance is .006-.008, I had one exhaust valve at over .015 and one intake valve at .004 or less. The engine noise was noticeable before the repair.

I reassembled the top end last night and got the engine running. It started immediately and runs as smooth as glass with good power and stable idle. After running for more than 30 minutes, the temp gauge just barely moved from the cold mark and the cooling fan never came on except when starting. I'll finish the RTV this weekend and put it to work. So far, I am out about $160.00 in parts and machine work.

Franz
 
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