Kubota v1505 overheating

[MrFritsch]

I’ve been battling this issue for over a year, it has been overheating since I purchased my mini excavator. I replaced the head gasket initially with no change. Then took the whole engine to the machine shop, put all new cylinder liners in, pressured checked the head, decked the engine and head. Replaced valves, water pump, thermostat and radiator. It still overheats and had blow by. So I replaced the head the a brand new one, no change. Just replaced the injectors with no change. It has an electronic lift pump, so I ordered a new mechanical one and will install that tomorrow. It heats to 230F in about 5 minutes of digging work, installed a mechanical temp gauge and checked it with a temp gun, and still has blow by. I’m at a loss idk what else it could be. I have over 3k invested in the motor and it still isn’t operational. Any suggestions?

 

[Welder Dave]

Maybe it needs a bigger radiator. How well is the engine ventilated?

 

[HarleyHappy]

You would have been better to spend the money on a professional radiator and cooler cleaning instead. What happens if you don’t do any digging and just run the machine at 3/4 throttle?
Try and find what’s making it overheat.
What happens if you just track around?
Should be able to narrow it down to engines or hydraulics.
Does this machine have a separate oil cooler or is it built in?
What is the ambient temperature when you are working it?
Does it heat up as fast if it is cold out?

 

[Welder Dave]

What mini excavator is it? If it's a cheaper off brand may not have been designed for optimal cooling.

 

[MrFritsch]

It’s a gray market Hitachi ex 35-2 about a 2003 model. I retorqued the head and adjusted valves per my mechanic today, thinking the new head gasket might not have sealed. No change, overheats and has blow by. I noticed lower rad hose is 30 degrees or more hotter then the upper. It’s about 65 degrees here, it’s gets up to temp quickly whether cold or hot outside. It overheats under load with hydraulic use. Last week I added an electric fan on the hydraulic cooler which is next to the rad. At full throttle just sitting there it runs about 190F, cools down under idle. I saw they make 2 different direction water pumps but I did pull the upper rad hose last week and it was pumping out.

 

[Welder Dave]

I wonder if it needs a specific thermostat or the thermostat is faulty. 190 isn't bad if it doesn't go higher.

 

[chidog]

New or old, did you test the thermostat? I'd be borrowing or renting or some how getting a good thermo camera and check the radiator, and every thing else. If this is a used machine/ engine, then maybe it has done this day one, could be something blocked internal or someone left a rag in there.

I'd be checking flow through everything.

 

[Simon C]

It’s a gray market Hitachi ex 35-2 about a 2003 model. I retorqued the head and adjusted valves per my mechanic today, thinking the new head gasket might not have sealed. No change, overheats and has blow by. I noticed lower rad hose is 30 degrees or more hotter then the upper. It’s about 65 degrees here, it’s gets up to temp quickly whether cold or hot outside. It overheats under load with hydraulic use. Last week I added an electric fan on the hydraulic cooler which is next to the rad. At full throttle just sitting there it runs about 190F, cools down under idle. I saw they make 2 different direction water pumps but I did pull the upper rad hose last week and it was pumping out.

I once worked on a water pump that was used for fighting fire, it was a two-stroke powered unit . It only produced 175PSI instead of the 270PSI of the second same unit . After changing out the pump we found out the recoil had been wound backwards and the pump was starting backwards. It was a Wajax unit.
If your water pump could turn backwards it would still cool, just not enough. Just a thought.
Simon C

 

[MrFritsch]

I put a new thermostat in it, checked it prior and it was working. Tonight I removed it, then flushed the block and radiator with a garden hose. It flew really nice both directions in both block and rad. Resembled but still overheated to above 200 after a few minutes when tracking back and forth. I pulled the cap and noticed the coolant wasn’t flowing as quickly as I would imagine for no thermostat. The water pump is new when I rebuilt the motor but I can pull it tomorrow and check if it’s slipping on a shaft. I used a regular temp gun to check the temps, I don’t have a thermal camera. I installed a new rad last week and there was no change, but reinstalled the old one because the fan shroud wouldn’t fit the new one

 

[MrFritsch]

Interesting you mentioned the reverse direction. A few weeks ago I thought of this. Looked up the water pump for the v1505 and it appeared to have pumps that spun in different directions but had the same part number.

 

[Welder Dave]

Impeller spinning backwards would make a huge difference.

 

[Nige]

I pulled the cap and noticed the coolant wasn’t flowing as quickly as I would imagine for no thermostat.

On most engines (not sure about this particular one) coolant won't flow correctly if the thermostat is not installed.

 

[Simon C]

Interesting you mentioned the reverse direction. A few weeks ago I thought of this. Looked up the water pump for the v1505 and it appeared to have pumps that spun in different directions but had the same part number.

Better make sure your impeller is not turning backwards or that is your problem from way back. Detroit Diesel made water pumps that could turn 2 ways for 2 different engines.
Simon C

 

[MrFritsch]

I’ll check it out tomorrow and make sure it’s spinning the right way and not spinning free of the shaft at high RPM. I just saw it has a 60 or 70mm impeller for the same motor. I installed the 70 last time

 

[Welder Dave]

Rad cap could be suspect too. What coolant are you using?

 

[Simon C]

Its not only the size of impeller, it is the direction of the flutes. Water pumps are non-positive displacement. If lower rad hose is 30 degrees hotter than the upper, something is wrong.
Simon C

 

[MrFritsch]

I replaced the rad cap this weekend suspecting that, no change.

I just read online to check proper impeller direction. Just noted that there’s 2 different size impellers and directions. I’m assuming go with the biggest size? Making sure it spins the right way of course

 

[Welder Dave]

Is the rad. cap the correct PSI rating?

 

[chidog]

The gauge is reading correct temp? The airfilter clean? Not over fueling? Does it act like a lot of load on it? Is it a turbo engine? Timing is all good?

What is radiator inlet and outlet temps with the hand held ir? You never said what the temps checked at.

Is there a bypass for quick warm up some place? Maybe too much by pass. All we can do is guess miles away.

 

[HarleyHappy]

You mentioned changing the radiator and that the shroud wouldn’t fit the new one.
One thing I have found with the Kubota engines, is that the cooling system is designed for optimum air flow. If you are losing any air flow around the radiator at all, this will affect the temperature. Make sure all the shroud and insulation, including the foam is in place.
Might be on the right track with the water pump also check to make sure fan is in correct rotation for a push or pull type fan.
Most Kubota are either push or pull and they sell fans for either direction for most motors they sell.
When I replaced the fan on my V2203 they had fans either way but most were pull type and I needed a push style.