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Topic: U225 Thermostat Problem? (Read 902 times) previous topic - next topic

U225 Thermostat Problem?

We're 350 miles from home and  the trip over all was fine until the main pass when coolant temp went up to 235 but came down to 200 and then climbed to 240 and suddenly dropped back to 200. This happened over and over until I stopped and let everything cool down. When I started back all was 180 until a big hill when the cycling of water temp started again. Another stop for lunch and temps were ok from then on.

I suspect a bad thermostat. I tried calling FT but the tech help guys we're gone. Do I need a special  thermostat or can I buy one at NAPA? Do I have to drain coolant or can I just remove a couple of bolts and lift it out? Does anyone think it's not the thermostat?

This temp problem started a month ago and seems to be getting worse. Air temps  the u70s for this incident.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: U225 Thermostat Problem?

Reply #1 –
As I recall it is a pretty standard 180 degree thermostat. I always bought mine from Cummins. I do remember that you cannot run the engine without a thermostat so don't try that. I always had Cummins install it because the location is on the drivers side back near the radiator and my body does not bend in that many places that I could get to it.I also recall that you lose some coolant but not a lot when you make the change. It is pretty high up on the engine.

You may also want to check and see if there is air in the cooling system before you change the thermostat. There should be a relief valve on the top most coolant pipe on the passenger side of the engine. Simply open it while the engine is at idle an see if any air comes out. If so, leave it open until coolant come out of the valve.  A partial air lock could be causing the problem. 
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: U225 Thermostat Problem?

Reply #2 –
What engine? I just did mine. 8.3c has 2.
1994 U280, Build 4490
Deming, NM.

Re: U225 Thermostat Problem?

Reply #3 –
Twig: it's the 5.9b Cummins.

Kent: thanks. FT was little help and suggested Cummins. I'll try the air trick first.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: U225 Thermostat Problem?

Reply #4 –
Looks like we'll be hitting Cummins in Portland on Monday. Sue and I looked at the engine and couldn't find where the thermostat goes; not in the obvious place and I suspect some stuff has to be removed.

I did open the petcock on the metal pipe leading from the radiator to what I suspect is the water intake to the engine but nothing came out at all even though the system is full of coolant (changed last year along with the filter). Perhaps the engine has to be fully up to operating temperature before bleeding it will work.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: U225 Thermostat Problem?

Reply #5 –
Craig,
The 5.9 Cummins thermostat is usually housed in the bracket that also serves as the mount for the alternator.  That is how it is on my 5.9 in a Freightliner FL60, no idea of the configuration on your coach. Take your engine number with you when you go to Cummins so they can look up the thermostat and gasket.
As for bleeding the coolant system, that is only needed once at most, when the system is filled, once it is filled and been working, it never needs re bled.
Some have a petcock/valve near the top radiator hose to bleed the air when refilled, open valve until you only have water and no air.  This is due to some systems will trap air, not allowing the coolant to fill up to the thermostat.  SO if you have lot of air in system, you can overheat it and the termostat will not open to get water flowing to the radiator.,  Gotta have the hot water going to radiator  :o
Enjoy
Dave M

Re: U225 Thermostat Problem?

Reply #6 –
Quote from: Dave M –
The 5.9 Cummins thermostat is usually housed in the bracket that also serves as the mount for the alternator.  That is how it is on my 5.9 in a Freightliner FL60, no idea of the configuration on your coach. Take your engine number with you when you go to Cummins so they can look up the thermostat and gasket.

Dave... I think mine is exactly like what you described. The bracket doesn't look like any other thermostat housing I've ever seen so I was mightily confused.

Quote
As for bleeding the coolant system, that is only needed once at most, when the system is filled, once it is filled and been working, it never needs re bled.
Some have a petcock/valve near the top radiator hose to bleed the air when refilled, open valve until you only have water and no air. 

Started engine, opened petcock on the metal piping leading from the radiator to that bracket that holds the alternator and nothing came out even though the system is full of coolant. I'll try it again once we're on the road and the engine gets up to full temp.

The overheat problem takes a while to develop... at least a couple hours of driving... and usually a big grade to get the coolant temp up into the 240 range. It will then cycle down quickly (like in 30 seconds) and cycle up slowly to 240 or so then, again cycle down quickly. Has every appearance of a poorly operating thermostat to me.

Will stop at Cummins in Portland in the morning... probably find a Walmart somewhere near Portland (Longview, probably) for the night. Cummins Northwest opens at 7am and if we can get there early and out early we can get home tomorrow night.

Thanks for all the tips!

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: U225 Thermostat Problem?

Reply #7 –
Quote from: wa_desert_rat –
Started engine, opened petcock on the metal piping leading from the radiator to that bracket that holds the alternator and nothing came out even though the system is full of coolant. I'll try it again once we're on the road and the engine gets up to full temp.

The overheat problem takes a while to develop... at least a couple hours of driving... and usually a big grade to get the coolant temp up into the 240 range. It will then cycle down quickly (like in 30 seconds) and cycle up slowly to 240 or so then, again cycle down quickly. Has every appearance of a poorly operating thermostat to me.

Will stop at Cummins in Portland in the morning... probably find a Walmart somewhere near Portland (Longview, probably) for the night. Cummins Northwest opens at 7am and if we can get there early and out early we can get home tomorrow night.

Thanks for all the tips!

Craig

Be very careful opening the petcock when system is under pressure. You could get burned.

Also, if you are in 100 degree temps and going up a long or large hill, the 5.9 can hit 240 under normal circumstances. You just need to not let it run that hot for very long. I always tried to pull over and let mine cool once it got to 220 but 240 is the absolute max.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: U225 Thermostat Problem?

Reply #8 –
Craig
Have you cleaned the radiator?  They can build up a lot of crap which stops the passage of the cooling air!!!
1994 U225
build #4514

Re: U225 Thermostat Problem?

Reply #9 –
Better question:  Have you cleaned the FRONT of the CAC-- that is where the dirt will be on this sandwiched rear radiator configuration.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: U225 Thermostat Problem?

Reply #10 –
Craig,
Interesting about opening the petcock at thermostat housing and NO water, you are sill LOW on coolant,  Let it open for awhile, might take a few minutes for the water to raise up to that level.  If the radiator is full and that level is above the thermostat housing you will have water flow from the petcock.  Even with the engine running, making water pressure, you should have a water flow out that open petcock. IF not, I would remove the petcock and make sure it is open, and if it is, run a screwdriver down into the housing, there is some reason you are not getting water where you need water.  IF the water level is below the thermostat, That AIN'T good, see why.
AS they say "This ain't rocket science"
Good luck
Dave M

Re: U225 Thermostat Problem?

Reply #11 –
Cleaned both sides of the radiators last week before  we left using Simple Green.

Peacock appears to be above the "COLD" level mark on the overflow tank. When I pop the radiator cap the radiator is full.  I could maybe squeeze in another liter or so.

Don't think it's a problem with coolant level; I just opened that peacock while the engine was cold.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: U225 Thermostat Problem?

Reply #12 –
Craig,

As long as you are taking the coach to Cummins, ask them to examine the fins on the radiator itself. At 16 years, many of the fins on my radiator had detached; it won't give you the same symptoms that you are describing, but given the age of your coach, it would be a preventative measure. We were stuck up in Billings, MT for a week while our radiator was re-built. When my thermostats cratered, the temp jumped up and down just as you have described.
Don Hay
'92 Grandvilla, U-280
The Hayfever Express
Build #4055
'97 GEO Tracker
Life is like licking honey off a thorn.

Re: U225 Thermostat Problem?

Reply #13 –
Craig,

The level of the petcock versus the overflow tank level is not relevant.  The coolant level should be up to the sealing flange on the radiator cap.  You certainly shouldn't be able to add another liter-in fact even an ounce.  Otherwise the overflow tank can't work.
Regards,
Brett

'99 42' Foretravel Xtreme
'14 Brown Motorsports Stacker
'05 Chevy SSR
'02 BMW R1150R

Re: U225 Thermostat Problem?

Reply #14 –
Ok... we're home. Decided to just head home and keep the temps under control by speed control.

This morning starting out the temps stayed at 180 and the heater was on and blowing hot air. The first hill sent the indicated temp to 225 and I started driving to keep temps low. Noticed that the heater was blowing cold air while the temperature indicated 225. I thought this was interesting.

Temperatures move up and down quickly. Up to 230 and down to 200 in a minute; sometimes less.

Temperatures do not always climb on a hill... even a steep hill. We climbed to the top of Vantage hill eastbound on I-90 (east of Ellensburg, WA) at 60mph at 180-degrees indicated all the way but climbing the next grade (on the east side of the Columbia River) put the system into up/down mode and speeds at 35 to 45 in 3rd gear (on a 4-speed Allison).

Temperatures sometimes do not rise on the climb but rocket upwards as we descend; even when there is no throttle input, no retarder, just coasting.

The rapid up/down of temperature indicates (to me) thermostat malfunction. But the heater blowing cold air when the water temperature gauge is indicating 230-deg seems to also say "water temperature sending unit".

Same road last June was at 60mph the entire way with only a few climbs below 50mph and zero temp problems. Ambient air temps today ranged from 60F at the start (7:30am) to 76F at the finish (11:30am).

I think I'll replace both the thermostat and the temperature sender.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: U225 Thermostat Problem?

Reply #15 –
Craig,
You know I have run into a similar issue many years ago, where the temp would act much like yours.  Turned out to be the water pump impeller was off the shaft.  Normal thermal cycling worked until needed more fuel/hp.  That would also explain why you could not get water from the valve at thermostat housing to bleed the air, no water pressure.  Cummins always have a lot of water pressure.
The good part, that water pump is very simple to replace, while your at it, check the belt and idler.
Dave M

Re: U225 Thermostat Problem?

Reply #16 –
I had sort of the same problem with the gauge showing all kinds of temps. 

I check with a heat gun the radiator, and found it was at a very nice 180 degrees.  I had cleaned the engine with hose water and Simple Green, including the front of the charged air cooler.  The temp sender is right on top of the engine in front of the charged air cooler.  After I changed my water temp sender on the engine, I have seen normal temp. swings on hills.  It is an easy change out.
Dave Cobb
Buckhorn Lake Resort The Club, #6202, Kerrville TX
check the map.  I do rent it out when I am traveling!
2001, U320, 36' #5887, in Kerrville, FT Club #17006, (7/23 to present)
2024 Jeep Grand Cherokee L, Summit, white
EX: 98 U295, 36' #5219, (mid door), (4/13-10/23)
EX: 93 U225, 36' (4/11 to 4/13)

Re: U225 Thermostat Problem?

Reply #17 –
Well, going to have to wait on the RV troubleshooting... I'll check with local Cummins shop about getting a thermostat, temp sender and maybe water pump. In the meantime we had a hose break on the blueberry irrigation system and our bedroom and the kitchen had a minor flood. Since our house is a "half-buried" sub-grade house this can be an issue but while it's happened to neighbors it's never happened to us 'til now.

Fortunately we have a carpet cleaning machine and have sucked up about 50 gallons of (very dirty) water with probably a few more to come. Will get a couple of big fans later today.

I wonder if that's two problems or three... hopefully another one is not just around the pike. :P

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."