Overheating

racefuel

New member

Equipment
RTV 900
May 11, 2021
8
0
1
Oklahoma
I got a deal on this 2004 Kubota RTV 900, 3 cylinder diesel D902. The issue with it is it got hot and overheated. Previous owner put in a new radiator, thermostat and replaced the head gasket. He wasn’t sure how to adjust the valve lash so not sure what he done there after reinstalling the head. It starts and runs great but temp gets almost to the red on the temp gauge in a matter of 2-3 minutes. Could the valve lash be the issue or something else internal other than maybe bad water pump or faulty thermostat? Also fan never turns on even as temp gauge comes up. Lower radiator hose cool and top hose just warm in that short amount of time. Thanks for the help!
 
Last edited:

DaveFromMi

Member

Equipment
L3901, 5' Bush Hog
Apr 14, 2021
47
29
18
Indiana
Check coolant level.
Hoses pressurized downstream of water pump. Pump good or not?
Check thermostat in hot water bath. Replace if necessary.
Check air intake for proper airflow.
Could exhaust be restricted?
Coolant fan sounds defective.
 

85Hokie

Well-known member
Lifetime Member

Equipment
BX-25D w/ Filled Rears,2" Spacers,PTB. Under Armor, 90'-90'-92'-B7100HST's
Jul 13, 2013
8,192
506
113
Bedford - VA
An cold engine cannot physically get that hot in 2-3 minutes ..........

radiator would not even begin to warm up - even a stuck thermostat would not allow an engine to overheat in that little time......... now five to ten minutes I would say yes......

you have a bad head gasket or cracked head or worse!

Open the radiator cap - look inside as engine is first started ............ bubbles or blowing out coolant?
 
  • Like
Reactions: 1 user

racefuel

New member

Equipment
RTV 900
May 11, 2021
8
0
1
Oklahoma
An cold engine cannot physically get that hot in 2-3 minutes ..........

radiator would not even begin to warm up - even a stuck thermostat would not allow an engine to overheat in that little time......... now five to ten minutes I would say yes......

you have a bad head gasket or cracked head or worse!

Open the radiator cap - look inside as engine is first started ............ bubbles or blowing out coolant?
An cold engine cannot physically get that hot in 2-3 minutes ..........

radiator would not even begin to warm up - even a stuck thermostat would not allow an engine to overheat in that little time......... now five to ten minutes I would say yes......

you have a bad head gasket or cracked head or worse!

Open the radiator cap - look inside as engine is first started ............ bubbles or blowing out coolant?
I took the radiator cap off as soon as I started it and it does push water out!
 

BigG

Well-known member

Equipment
l2501, FEL, BB, Rotary cutter, rake,spreader, roller, etc. New Holland TL80 A
Sep 14, 2018
1,563
434
83
West Central,FL
Could the gauge or the sending unit be defective? If the fan is not coming on nor is the bottom hose hot.
 

85Hokie

Well-known member
Lifetime Member

Equipment
BX-25D w/ Filled Rears,2" Spacers,PTB. Under Armor, 90'-90'-92'-B7100HST's
Jul 13, 2013
8,192
506
113
Bedford - VA
I took the radiator cap off as soon as I started it and it does push water out!

there is your answer - there is a crack in the head or possible the cylinder wall(s) - betcha a cracked head.
Could be a head gasket again ..... but I bet not

The explosion of diesel forces that into the coolant pathways and thus pressurizes the cooling system - since the gas is super hot - the water does not get hot but the sensor reads hot.

I would not run the tractor any more ....... time to tear it down and have it inspected.
 
  • Like
Reactions: 2 users

racefuel

New member

Equipment
RTV 900
May 11, 2021
8
0
1
Oklahoma
Could the gauge or the sending unit be defective? If the fan is not coming on nor is the bottom hose hot.
I thought the same thing and wanted to just let it run after it hit the red but thought I would check a few things first. All the basic stuff looks good. Antifreeze, belts, hoses etc.
 

racefuel

New member

Equipment
RTV 900
May 11, 2021
8
0
1
Oklahoma
there is your answer - there is a crack in the head or possible the cylinder wall(s) - betcha a cracked head.
Could be a head gasket again ..... but I bet not

The explosion of diesel forces that into the coolant pathways and thus pressurizes the cooling system - since the gas is super hot - the water does not get hot but the sensor reads hot.

I would not run the tractor any more ....... time to tear it down and have it inspected.
ok, thanks for the help! Guess it’s time to pull the head off.
 

GeoHorn

Well-known member
Lifetime Member

Equipment
M4700DT, LA1002FEL, Ferguson5-8B Compactor-Roller, 10KDumpTrailer, RTV-X900
May 18, 2018
2,491
686
113
Texas
The RTV (X900..same engine) has a cooling-system “breather” .... a vent-vlave behind the drivers seat on top of a 3/8” rubber hose. If the coolant is added after any kind of engine work,... as soon as it is started...that breather/vent must be manually opened to let air out of the system, and then top-off the system.. or it will overheat within minutes....possibly blowing the head gasket (or if done repeatedly or severely may crack the head.)

Even tho’ the overflow reservoir is full...the system will not suck colant back into the radiator to make up the low coolant level until that breather/vent is opened and the air expelled.
DA1A26A4-BDE9-4F31-BFDF-2A75AC53884A.png
 
Last edited:
  • Like
Reactions: 1 user

racefuel

New member

Equipment
RTV 900
May 11, 2021
8
0
1
Oklahoma
The RTV (X900..same engine) has a cooling-system “breather” .... a vent-vlave behind the drivers seat on top of a 3/8” rubber hose. If the coolant is added after any kind of engine work,... as soon as it is started...that breather/vent must be manually opened to let air out of the system, and then top-off the system.. or it will overheat within minutes....possibly blowing the head gasket (or if done repeatedly or severely may crack the head.)

Even tho’ the overflow reservoir is full...the system will not suck colant back into the radiator to make up the low coolant level until that breather/vent is opened and the air expelled. View attachment 59743
Thanks for the tip! I’ll check on that.
 

GeoHorn

Well-known member
Lifetime Member

Equipment
M4700DT, LA1002FEL, Ferguson5-8B Compactor-Roller, 10KDumpTrailer, RTV-X900
May 18, 2018
2,491
686
113
Texas
Thanks for the tip! I’ll check on that.
The way I discovered this issue was when I found a loose clamp on the system (on a hose-to-pipe which passed underneath the cabin) that had dripped onto the floor. I had to drain the system to clean corrosion off the pipe during that repair, and I re-filled the system completely.... or so I THOUGHT!
My overflow reservoir was almost full, and I completely filled the radiator and I started ‘er up and when the thermostat opened up and the radiator tank level dropped.... I topped it off again. It was FULL...and the overflow reservoir was almost full.
I was ready to go riding and so I let the wife drive. We didn’t get 1/4 mile down the road when the high-temp alarm went off and the temp gauge was AT THE TOP of its’ range in the overheat range. It was only A few minutes for it to overheat.

I was really surprised to see that the radiator tank was low...and the overflow reservoir was still almost full! That made no sense to me. Pulling out the WSM, I discovered the little “breather” comments and illustration.
Opening that breather valve allowed me to “for real” top-off the radiator. Now-truly-full.... no more overheating issues.

Hope this helps.
 
  • Like
Reactions: 1 user

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
2,858
314
83
Mid, South, USA
the radiator cap is a pressure cap

when the pressure in the cooling system exceeds the pressure rating of the pressure cap, it relieves the pressure into the overvflow bottle.

Conversely, if the overflow has coolant in it, when u turn off a hot engine, the coolant will contract, which causes the pressure cap to allow coolant to be drawn back into the system, thus creating a closed system.

--BUT--

for everything to work, everything except the overflow bottle has to be sealed up good. A crack in the cylinder head causes an air leak of sorts. Combustion pressure leaks out (and causes aeration and overpressurization of the cooling system), AND the cooling system won't "suck" coolant back in as it cools down.

Kubota heads crack pretty easily after an overheat event. So don't overheat them.

On the 900's, they don't have that bleeder. X900's do.

On the older 900, prepare yourself to replace these items if you coolant is or was every rusty-looking:

radiator
water pump
thermostat
head
head gasket
ALL hoses (including the little one from the water pump to the pipe)--and on some RTV's also the trans oil cooler hoses.


and you'll also need to flush the block out, and clean the junk in the passages at the top of the block--they get plugged with scale (rust) and will also contribute to overheating. These are often overlooked by even seasoned techs.

why replace the hoses? Because junk coolant conducts electricity, which causes the hoses to soften and eventually they'll leak. Sounds crazy but it happens. Often. Also contributing is the fact that combustion gases have gotten into the system which also causes the hoses to soften.
 
  • Like
Reactions: 1 user

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
2,858
314
83
Mid, South, USA
Just got my 1100x and having the same issue. Is there a valve to expel air on the 1100?
which 1100 do you have?

RTV-X1100's have a bleeder on the back of the cab, left side I think. Has a hose attached to it.

RTV1100's do not have this.

Air isn't a big deal on the RTV1100's as long as the head ain't cracked and the gasket ain't leaking. Typically fill the system, start it with the cap off, and let the bubbles subside-shouldn't take more than a minute. Shut engine off, refill, cap it, and then top off the puke bottle.

On the RTV-X1100, the radiator is out front and lots more hose volume, that's why the bleeder is there.
 

JerryMT

Member

Equipment
Kubota M4500, NH TD95D,Ford 4610
Jun 17, 2017
234
7
18
The Palouse - North Idaho
I got a deal on this 2004 Kubota RTV 900, 3 cylinder diesel D902. The issue with it is it got hot and overheated. Previous owner put in a new radiator, thermostat and replaced the head gasket. He wasn’t sure how to adjust the valve lash so not sure what he done there after reinstalling the head. It starts and runs great but temp gets almost to the red on the temp gauge in a matter of 2-3 minutes. Could the valve lash be the issue or something else internal other than maybe bad water pump or faulty thermostat? Also fan never turns on even as temp gauge comes up. Lower radiator hose cool and top hose just warm in that short amount of time. Thanks for the help!
"...Lower radiator hose cool and top hose just warm in that short amount of time. ..."

If this is so and the gauge is in or near the red line then there is most likely a problem with the temperature sensor.