RK55H Hot Gas Tank

[g8erh8er]

I'm dealing with a hairline crack in my gas tank and noticed yesterday while checking on my patch job that after about 2 hours of mowing, the tank was extremely hot to the touch, like uncomfortably hot.

I don't recall my gas tank getting hot like this in the past, but then again I'm not sure I've ever made it a point to check its temp. Can anyone else confirm there's gets hot as well? I know the fuel filter has a line on it that will send gas back to the tank, just didn't realize the fuel would be sent back that hot.

2019 RK55HC with 570 hrs

 

[dodge man]

Just to be clear diesel correct? Where is the tank? If it’s near the engine or exhaust I’d say that might be normal. Uncomfortable hot seems a little unsafe. If it’s away from the engine and exhaust that doesn’t seem normal. A fairly large amount of fuel is returned to the tank and it will get warm passing through the engine bay but it shouldn’t be hot.

 

[g8erh8er]

Just to be clear diesel correct? Where is the tank? If it’s near the engine or exhaust I’d say that might be normal. Uncomfortable hot seems a little unsafe. If it’s away from the engine and exhaust that doesn’t seem normal. A fairly large amount of fuel is returned to the tank and it will get warm passing through the engine bay but it shouldn’t be hot.

Diesel. Here’s location of the tank relative to the engine. Seems like fuel is returning to the tank way too hot. No egine over temp warnings or anything like that though, and tractor runs good. I’ll have to use my temp gun on it next time to get an actual number.

 

[ptsg]

Your tractor has a Common Rail engine, which pressurizes the fuel to extremely high pressures, up to 40,000 PSI in some engines.

Pressurizing any type of fluid to high pressures will cause the fluid to heat, a lot. That's why they typically run a fuel cooler in common rail engines.

Checking the parts catalog for your tractor, I couldn't find one, so that would explain why the diesel tank gets so hot. Even with a cooler, the fuel temp typically sits in the tank at around 130F, give or take. So without a cooler, I can only imagine it getting much hotter.

 

[RjCorazza]

I would be interested in hearing what temperature you get on the fuel tank. My Kubota common rail has a cooler, and I have never noticed the tank getting particularly warm.

 

[g8erh8er]

Thank you for the explanation. You’re correct my tractor only has an oil cooler. Kinda seems like a design flaw to have 15 gallons of very hot fuel sloshing around in a thin walled plastic tank that’s getting vibrated, bounced, etc. No wonder mine has a crack.

 

[g8erh8er]

I would be interested in hearing what temperature you get on the fuel tank. My Kubota common rail has a cooler, and I have never noticed the tank getting particularly warm.

It’ll be another two weeks before I mow again but I’ll let you know. I will say I could only hold my hand on the portion of tank below the liquid line for a second or two before the pain was too great, so my guess is it had to have been in the 130-150 range.

 

[CloverKnollFarms]

What's interesting is that TYM makes this model, but the TYM is not common rail. RK specs a different engine that is... But must have forgotten to request a fuel cooler. Whoops

 

[ptsg]

This RK55 is rebranded from the TYM T554 which had indeed a common rail engine. This series of tractors was before TYM started using the Kukje mechanical engines in their models.

The T554 also didn't have a fuel cooler.

 

[CloverKnollFarms]

Oh. I thought todays RK55 was otherwise identical to the TYM 574

My bad. Sounds like TYM f'ed up.

 

[ptsg]

Which makes me wonder if RK is planning on updating their line of tractors since the current series they sell have been discontinued last year.

 

[dodge man]

I had to Google if liquids get hot when compressed. I always thought of liquids as incompressible, which is mostly true. Compared to gases they don’t compress much but enough to generate heat. Not as much as gasses but when the fuel gets compressed it heats up, the excess returned to the tank, and this happens over and over I can see how it gets hot.

 

[CloverKnollFarms]

Seems the hot tank is the least of ones worries. Wow.

AI Overview:
Common rail diesel engines have fuel coolers to prevent fuel degradation and maintain optimal performance. High-pressure fuel injection in common rail systems generates significant heat. This heat can degrade the fuel, leading to deposits in the fuel system, reduced lubrication, and potential damage to fuel pumps and injectors. Fuel coolers help to dissipate this heat, ensuring the fuel remains within acceptable temperature ranges and maintains its lubricating properties.

 

[JTKub]

I had to Google if liquids get hot when compressed. I always thought of liquids as incompressible, which is mostly true. Compared to gases they don’t compress much but enough to generate heat. Not as much as gasses but when the fuel gets compressed it heats up, the excess returned to the tank, and this happens over and over I can see how it gets hot.

A lifetime ago I worked in R&D for a pump manufacturer who made pumps for Navy and commercial ships. We would set up test rigs for them. Just pumping water through a test loop in/out of a ~10k gallon test tank could heat the water to the point of boiling it if you let it go as is long enough.

 

[WM75Guy]

Maybe you could pipe in a fuel cooler. Pressurizing a liquid will cause it to heat up. On fire trucks the water in the pump would heat up past the boiling point and cavitate if we didn't have water flowing, to the point of destroying the impeller. My NH WM75 22 gallon fuel tank is in the same location as your tank. My tractor does have a fuel cooler. Must be why I never noticed any heat when climbing out after mowing.

 

[Harrygoodwrench]

You said you could only hold your hand on the tank for a few seconds due to it being hot.
Consider this, your shower water set at 120 degrees will almost scald you so you must really use your temp gun to find out how hot it really is before condemning anything.
Temperature is relative to animate objects (people).

 

[Jtschnel]

It’ll be another two weeks before I mow again but I’ll let you know. I will say I could only hold my hand on the portion of tank below the liquid line for a second or two before the pain was too great, so my guess is it had to have been in the 130-150 range.

You might want to consider running it now to check the actual temp so you could address/fix the issue if necessary before you need the unit again.

 

[jigs_n_fixtures]

The heating is a function of the pump inefficiency. If a pump is 90% efficient the 10% becomes heat. Might look at an inline oil cooler.

Patching the tank: Get a plastic welder, basically a heat gun with a feed tube to feed plastic rods onto the plastic your fixing as it melts the rod, and part your fixing. Odds are the tank is HDPE, and kits to weld it are readily available. Same basics as stick welding. But leave the bead proud, and clean it up with a sharp block plane.

 

[banjoman69]

I’ve got an Rx6010c with 540hours , bought new , left tank started leaking around 460hrs. I took it off (priced a new one $500+) so I rigged up an air hose to it, applied about 15lbs pressure, , found the exact spot of the leak.
Cleaned the area squeaky clean, roughed it up, cleaned again and used an old plastic fuel container that I cut in thin strips to use to “weld” with. I used a soldering gun and fused the seam together, then packed or spread the melted plastic on top of all that. I used an old bike tube as a cushion for the strap on top of the original and put it back on. I figured if I bought a new tank, I’d be out the $500 again in a few yrs, so I decided to do a fix. So far so good. Bad design on Kioti imo

 

[Frxdy]

I've found that I can *gently* hold my hand on 140-145 degrees F, but I can not, even gently, hold my hand on above 145. I can't imagine above 145 being allowed in a plastic tank. But... I'm not a plastic expert.