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Old 05-22-2014, 05:21 PM   #1
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Diesel pusher overheating

Hope to find some ideas re a heating problem. I have a 35'1993 Riviera diesel pusher with the 5.9 Cummins and 6 speed Allison trans. Bought the rig last year with 36,000 miles on it. 31,000 of those miles were by the original owner who was meticulous with his maintenance and record keeping. The last 5000 miles the unit has an unknown history. I drove it home to Moab from Las Vegas in 100 degree temps and had times where I was pushing 220 degrees while climbing. Slowing and downshifting and running at 2100 to 2400 RPM helped but not a lot. Got it home and did a complete service on the drivetrain which included new belts,hoses, internal radiator flush, new coolant, new thermostat and a thorough exterior cleaning of the radiator and CAC after researching on this site. Just got back from a fishing trip towing my 21' aluminum boat in 90 degree temps and had the same heating concerns as before. Runs great at 180 degrees on flat ground but any sustained climbing will send it to the 210 to 220 range. Have looked at a lot of good info on here but still feel like there is something I am missing. One site said the normal service life for a DP radiator is 10 years ? Any thoughts on this before I pull the radiator and have it professionally cleaned and checked. My other question is about auxiliary electric cooling fans. I have plenty of room to mount one on the outside of the radiator but not sure if I want to push or pull ? Any help or suggestions are greatly appreciated. Great site and resource!!
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Old 05-22-2014, 05:44 PM   #2
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My first thoughts zeroed in on the thermostat. Look up the factory specs for that engine set up. It is possible that the thermostat that you replaced was not the correct one, and if you replaced with the same spec item, the problem would still exist. I'm not saying this IS the situation, but I'd try to get another thermostat before doing more drastic things. As for the electric booster fans ... well recently I did some deep research on that idea too. Without going into a long explanation, my diesel mechanic and I decided against messing with the factory designed cooling fan system. We contacted fellows who had marginal to bad results with the electric fan idea.
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Old 05-22-2014, 05:53 PM   #3
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My guess would be that your radiator is probably plugged up. Even doing a radiator flush would probably not get it clean. Go to a radiator shop and have them check it out. If you have good temperature on level ground, the thermostat is working fine.
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Old 05-22-2014, 05:59 PM   #4
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Rimrock,

Give Scott Zimmer a call @ Source Engineering and talk with him about your over heating concern.

He's the man when it comes to engine cooling.

Dr4Film ----- Richard
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Old 05-22-2014, 10:06 PM   #5
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I feel your pain. I do believe there is nothing wrong with your coach as we have a 94 Riviera (By Cobra) 5.9 Cummins and have the same problem. I think they put in a rad from the factory that is too small. I've changed my thermostat, belts and hoses and had my rad re-cored to the tune of $1500.00 took it out and reinstalled it myself and it still runs hot when climbing hills in warm weather, after cresting the hill going down the other side it cools right down. If the weather is cool or it's raining it stays at 180 deg no problem. I've learned to live with it, 220 deg won't hurt it as long as it doesn't go any higher. Have had it for 10 years. Love the Rivera but upgraded to a newer bigger coach so it is now up for sale. They are great motor homes, has treated us well and we will miss it when she's gone.

Happy travels!
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Old 05-23-2014, 05:57 AM   #6
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I'd have a second look regarding the rad's ability to pass air through it? Ours was doing the same thing when we were out there, due to the PO's complete ignorance of the slobber tube issue.

With the engine running on a high idle, take a 12" piece of ribbon or something, and hold it in back of the rad. It should blow straight out anywhere you place it. I'm guessing you'll identify spots where it does not. Quick and easy test that can identify a big issue.
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Old 05-23-2014, 06:56 AM   #7
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Thanks

Thanks for the replies. One thing I forgot to mention was there was a reference to overheating in some receipts from the original owner when the coach only had 7000 miles, no explanation of what was done to address it under warranty. Also when I bought the unit there was a homemade ducting system made out of dryer vent hose and vent scoops that looked to try and scoop air from the front of the motor area in to the rest of the engine compartment. I removed that setup as it seemed to me to be collecting hot air from the pavement and exacerbating the issue. Was there no improvement when MDpuff upsized and recored his radiator Any more info re auxiliary fans would be helpful, it just seems that an ability to increase the airflow would have to help but info is scarce. Have talked with several electric fan manufacturers and they have not been a lot of help in regards to an install in a DP. I agree that 220 is acceptable for short periods but still would like more of a safety margin. Will start with pulling the rad and getting it checked and go from there. Thanks
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Old 05-23-2014, 12:25 PM   #8
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My 5.9 cummins in my dodge ram allways got hot when climbing pulling my 33 ft toy hauler, I f.ound 2 problems, first the fan clutch was not working properly so at high rpm when climbing the clutch was slipping, but on flat ground with lower rpms no problem, 2nd problem was the exaust, unless you have a 4" exaust from the Turbo back the exaust system cannot remove the heat fast enough from the engine, as a bonus it makes more horsepower and helped my fuel mileage when towing by about 1 MPG better. If you don't have an exaust temp gage installed at the turbo you should install one, it is very easy to melt a piston if as you say your engine water temp is 220 your engine must be really really hot. My dodge had the engine replaced in the first 20k miles because a piston top came off while towing uphill and I firmly believe it was jsut too hot.
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Old 05-23-2014, 12:51 PM   #9
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My 19 year old side radiator rig runs at 210 to 220 degrees uphill in 90 plus degree temps. The thermostat is not fully open until 205. It has done so for 12 years.
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Old 05-23-2014, 01:04 PM   #10
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Quote:
Originally Posted by deandec View Post
My 19 year old side radiator rig runs at 210 to 220 degrees uphill in 90 plus degree temps.
deandec

Same for my 18 year old rear radiator 3126 Cat powered coach.
Mel
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Old 05-23-2014, 05:04 PM   #11
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Got the radiator out today which was quite a chore and what little visual I can do it does to seem to have a lot of deposits built up. Will take it to a rad shop and hope it just needs a good cleaning. On the plus side it is a lot easier to do a good cleaning of the CAC with the radiator out. Will let you know what I find at the radiator shop and final outcome once it is buttoned back up and tested. Thanks again for the ideas.
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Old 05-23-2014, 05:25 PM   #12
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Quote:
Originally Posted by Rich and Cork View Post
My guess would be that your radiator is probably plugged up. Even doing a radiator flush would probably not get it clean. Go to a radiator shop and have them check it out. If you have good temperature on level ground, the thermostat is working fine.
I think he will find the air path blocked up on the radiator.

Quote:
Originally Posted by ahicks View Post
I'd have a second look regarding the rad's ability to pass air through it? Ours was doing the same thing when we were out there, due to the PO's complete ignorance of the slobber tube issue.

With the engine running on a high idle, take a 12" piece of ribbon or something, and hold it in back of the rad. It should blow straight out anywhere you place it. I'm guessing you'll identify spots where it does not. Quick and easy test that can identify a big issue.
X2 on that!!

Quote:
Originally Posted by rimrock View Post
Got the radiator out today which was quite a chore and what little visual I can do it does to seem to have a lot of deposits built up. Will take it to a rad shop and hope it just needs a good cleaning. On the plus side it is a lot easier to do a good cleaning of the CAC with the radiator out. Will let you know what I find at the radiator shop and final outcome once it is buttoned back up and tested. Thanks again for the ideas.
I'll bet you found the problem right there. remember its 21 years old. I'd bet its got 15 years or dirt build up on it.

The fact it runs cooler on level ground shows the thermostat is fine.
I have never seen one get weak, or go bad only on hills.
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Old 05-23-2014, 05:49 PM   #13
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My diesel mechanic was working on a MH that some people had bought in Seattle last week and drove it home to Spokane. They had to stop 5 times and let it cool down. (The DW was still hot about it when they got home and didn't want anything to do with it any more.) When he dropped the radiator the inside of it was 90% caked with dirt and oil. You couldnt' see it because it was on the inside. The outside looked clean as a whistle. No dobler tube had been installed and the oil overflow was sucked back up into the radiator and the only way you could see the blockage was when he took the radiator out. He said he doesn't know how any air got through it. Hopefully the new owner will be able to get his DW back in it!
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Old 05-24-2014, 10:33 AM   #14
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This is a pusher radiator so the oil breather probably vents in front of the rad. I extended mine after my rad. caked up on the inside. A good carwash will clean it right out and now that I by-passed the oil vent, problem solved.
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