Foretravel Owners' Forum

I have been trying to determine the correct thermostat for our PT 10 Kw generator, seems to be some discrepancies or misinformation concerning the correct t-stat between Power Tech recommendations and the owner's manual for the PT 8 - 10 -12 generator.

According the PT rep on the phone I should use part #03THM905K for our model number PTS MH-10FT. They also were given the gen set serial number. According to said manual this is a V1505 Kubota engine, which according to Kubota uses a 15531-73010 thru 15531-73014 t-stat. These are both a 2" version and not the 2-3/8" version (measured from centers of mounting bolts) and 180 degree rated. According to the Power Tech manual for the PT 8, 10, 12 KW generators used in RV applications the t-stat should be 160 deg rated and full open at 185deg.

Copied from the manual (sorry for the format, couldn't copy / paste the chart) :




Foretravel must have lowered the temp rating because of heating problems from being mounted in the enclosed generator box.
I am now trying to find the correct Kubota part number for the 2 inch version rated at 160 deg.
The 15531-73014 is the 2" 180 deg
The 19434-73014 is a  160 deg but have not been able to determine if it's a 2" or 2-3/8"

I will research this more tomorrow............ eyes are starting to cross and glaze over........

If you are doing this yourself and can wait a few days just pull the old one and see which one it is.IF both thermostats open all the
way at 185 it won't matter which one you use,if the engine overheats the thermostat would be open.If from what I read there is a 5
degree difference either one would work.One would just be open sooner.Do you have a problem or changing it for GP?

I replaced the original a couple years ago with the one that Kubota recommended for that engine. It's a 2" bolt to bolt diameter and 180 deg, same as Power Tech stated was correct for that engine. The Power Tech manual for the PT 8,10,12 KW generators recommends a 160 deg thermostat for generators in RV applications.

If the 160 deg is full open at 185 deg.............. then at what temp does the 180 deg full open?  205?

When we were staying at Fruita campground in Capitol Reef NP, temps were in the mid to upper 90's and we had both AC's on, after about 20 minutes the generator shut down and the radiator over flow tube spilled out about a pint of coolant. I let it cool down a bit and restarted it with only one AC running. It didn't shut down again but ran at 200 degrees according to two different infra red probes.

My thoughts are it should be able to handle both AC's running and other various loads no matter the outside temps without an overheating problem. I have cleaned the radiator and it appears to be clean and free of dirt and no obvious scale or buildup in the part of the tank that I can see. New radiator belt and it is tight with no slippage. Fan is in good condition.

Plans are to replace the water pump and install 160 deg thermostat. If I can locate one.........

If from 2 years ago til now it was ok the thermostat was good.The thermostat could be stuck,is your air filter clean?Our 8kw runs
about 177 at the oil filter and if I measure at the radiator the hottest is about 150 with my IF gun.Could the fuel filter need changing
and is the rad cap in good working order,how many hours on the gen?

Sounds like the belt for the generators water pump is worn/loose?

Reply #2 said belt is tight.

First noticed the problem on our trip out west in the summer 2016, really had no true test of running it in 95 deg and above heat until then. It doesn't have a problem with overtemp if ambient is below about 90 deg. Run all the loads no problems. Only in high ambient temps.  Changed the oil, oil filter and fuel filter just before we left on our trip this year. Air filter was installed new before 2016 trip.

Radiator cap appears to be OK, the overflow bottle level fluctuates as it should between hot and cold. no spill over unless it overheats and shuts down. after that I always make sure radiator is full when cold and bottle is at cold full level.

I had an earlier problem with it running above normal temp while traveling but normal when stopped. Gary O. sent me a PM to call him and we discussed the issue of the air deflector under the coach in front of the fan exhaust. Mine was there but it had come unattached at the front or leading edge. This allowed the air pressure from the underside (airplane wing effect) to push the deflector partially closed and restricting the fan exhaust air flow. A strip of Gorilla duct tape across the front of the deflector  effectively attached the front to the coach belly and prevented it from partially closing. (band-aid fix for now). It now runs the same temp whether moving or stationary whereas before it would run cooler while parked.

When I removed the original ( 4th owner so not sure about that) thermostat after the 2016 trip, I didn't notice what rating it was, could have been a 160 deg, but I installed a 180 because that was what Kubota had recommended.

Generator has around 2200 hours on it now and around 1550 when we purchased it in 2015.

Thanks for the replies, I'll keep researching the 160 vs 180 rating issue on RV applications.


 

Belt was replaced since I purchased the coach, will have to check records but it probably has less than 500 hrs on it.
Re-tightened it before last trip.

Where are you taking the temps from and what oil are you using?

The 200 deg reading at the campground that day was after it had shut down and I opened the bay door to inspect. Went back inside to retrieve the infra red probe, came back out and started it up. 200 was at the t-stat housing, about 190 at the side of the engine block.

I have installed a remote gauge at the dash and it always reads about 20 deg higher than the laser prob. Only realized in the last couple of days as to why. The thermistor for the gauge is installed just below the t-stat, so its actually reading the outlet water temp and not actual engine temp. The day it over heated the gauge actually was at 240 deg., even though a few minutes later the laser probe read only 200 at the t-stat.

I use Delo 400 15W-40 in most all my diesels........... trucks and tractors.

I'm not a foretravel owner however have been in the power generation field for nearly 40 years.  My opinion on thermostats is the 180 should be fine.  Power tech likely has dropped the stat temp to gain a little head start on the heat removal process.  Generally, overheating problems stem from inadequate air flow across the radiator and this could be a design issue.  Remember, the delta t across any radiator is 12 degrees at best and gaining a head start by opening earlier can keep you from reaching shutdown temps.  If the ambient is high, then the coolant temp is going to run higher also.

I think addressing the air flow especially the recirculating air (if any) is worth looking into.  Also build up of minerals inside the radiator can reduce the heat transfer so, if this is a new problem and the radiator is older, it might be worthwhile the remove and have the interior cleaned.

I hope you can sort this problem out.

Gordon

Thanks Genman,don't go away.

I found the original (as far as I know) thermostat today. I had changed it out in 2016. It is a 71*C or 160 *F rated stat. It's the smaller of the two t-stats that are used on the V1505 Kubota, about 1-1/2 " in diameter.
If I can find a 1-1/2" dia 160* .......
I'll replace it and the original water pump, if that doesn't solve the issue then I'll pull the radiator as suggested for cleaning or rebuild. 

This pic is the one PowerTech suggest as a replacement but I bought from Kubota

It is the correct size ( 1-1/2" dia) but it is a 180*
Instead of a 160*

Good to see you here Gordon!  I'm sure you can offer lots of tips and help.

Is the 12 degrees delta t on the water side? Seems low for the air side.

Not sure on that radiator but is there any way you can look inside where the cap is and see the passages?It does sound like it's
not getting enough cooling capacity.

From what I can tell from rolling the generator out and looking down thru the cap it looks free of scale or build up.

A follow up on the correct thermostat for the Kubota powered generator.
Ours is the V1505 4 cylinder with the 10 KW PowerTech, it came with a 71*C (160*F) thermostat. There are two different T-stats for this engine, the "small" 2" dia between bolt holes on the housing and the "large" 2-3/8" dia. According to Jeff at Power Tech they use the small diameter one on their gensets. PT's part number 03THM905K. When I ask if this was a 71* or a 82* rated T-stat he said he thought they were 71* but he would check. He pulled one off the shelf and opened it to find it was actually a 82*. Jeff was a bit puzzled and said he had one on his desk and would go look at it too. When he returned he said it was a different color and had a 71 stamped on it. BOTH were the same PT part number but different Kubota numbers. He said then that he would have to look into this further to see why they had two different parts listed under the same 03THM905 number.

The correct part for MY generator is the 71* "small" and gold colored - part #1E399-73010

The recommended T-stat for the 1505 engine by Kubota is the 82*  silver colored - Part #15531-73014

The 160* t-stat full opens at 185*, to the best I can determine the 180* full opens at 205* which may allow the engine to reach overtemp before full flow of coolant, as Genman had stated in an earlier post.

I will try out the new t-stat next weekend on a short trip to central Florida, should be hot enough to give it a good test.

I am updating this old thread, finally fixed the on going overheating problem last week with the removal and thorough cleaning of the radiator inside and out. I have slid the genset out and cleaned the radiator several times using an air hose to blow out (from the discharge side) to the inside. From the discharge side it appeared to be clean and with the shroud in place not much of the intake side of the radiator is visible. After NOT seeing much dirt or dust come from the radiator, I ASSUMED it was clean enough. Not the case!

Last week I removed the radiator to send it to the radiator shop to be cleaned internally and flow tested. I also wanted to replace the water pump while the radiator was out. I was surprised (shocked  :o ) to see the dirt accumulation in the fins hidden behind the fan shroud. It was an oily/greasy accumulation not removed with an air hose from the back side. Off to the radiator shop it went.
Water pump was removed and replaced along with the two associated hoses and small metal tube between the pump intake hose and the lower radiator hose. It had some rust under the hose connection and was pitted enough that I didn't trust it long term.
Also replaced the idler pulley/bearing combo while it was easily accessible. I had replaced the fan belt a year or two ago, it looked fine.

Now for the cause of the oily/greasy mess on the radiator.  ???
The slobber tube on the Kubota runs down the back side of the engine about 18" or so to about the level of the oil pan. I guess FT didn't see this as a problem but they call them slobber tubes for a reason. It only then dawned on me where this oily mist discharging out of this tube goes! Sucked up by the fan and blown out thru the radiator. There is no oil below the genset on the coach floor but it definitely doesn't stay clean. Kinda black and greasy after a while. Regular cleaning and no problem. Radiator is a different story. ::)
What to do with the slobber tube?
Here is what I did, right or wrong, it's done and I'll see if it helps.
Removed the old tube and purchased 3 feet of 5/8 fuel line. Drilled a hole thru the floor in the gen bay the size of 1 inch pvc conduit. Made 2 slip rings by cutting 1/2" off of each end of a 1" pvc coupling. Stuck a short piece of 1" pvc conduit thru the floor with a slip ring top and bottom and used adhesive caulk to seal top and bottom after gluing the slip rings on the nipple. Made a 1" 45 deg and coupled it to the nipple thru the floor. Stuck the 5/8 fuel line down in the 1" pvc (nice tight fit) and clamped it to the slobber tube discharge fitting at the top of the engine. Now what ever blows out the tube won't be inside the generator box.
I know this description may be confusing so I'll attach a few photos to show the end result.

Two rules on changes/extension to crankcase vent tubes= slobber tubes.. This applies to the main engine as well when adding  extensions and/or "catch containers":

1.  Do not reduce the CFM's-- if extending much longer, go up a size/diameter.

2.  Do NOT, form a drip loop with the extension.  Water vapor is a normal byproduct of combustion.  If operated in below freezing temperatures and you have a sag/drip loop, the water vapor can condense and freeze, blocking crankcase venting.

Check............ and Check......... old was 1/2............... new is 5/8 with no drip loop. ^.^d
thanks for the reply, advice always appreciated!

I like the 180's on everything because in the winter or cold months, it needs to get to 180 for everything to flow and keep clean. Just my 2 cents worth

I agree.  160 degrees F is too low for a diesel engine.  180 is fine.

Foretravel must have had their reasons.......... possibly due to the confines of the enclosure? As stated in a post above maybe it was to get a "jump" on the temp rising too fast under startup and full load as not to reach "shutdown" temperature.
Don't know, but mine now runs close to 180 using and IR gun even with the 160* stat and both AC units running.
T-stat  specs show the 160* full opens at 185, so I'm good with it.