Friday, December 1, 2023


Turbo diesel engine overheats. RVer wonders why


Dear Readers,
I received this email from reader Don Self about overheating problems with his turbo diesel engine. If you would like to offer Don a tip, please leave a comment. Perhaps you’ve had a similar experience. —Chuck/editor

Don Self

Don wrote:
In 2007, I bought my first RV (5th wheel) and a new turbo diesel one-ton pickup the same day to pull it. Since then, for my business we’ve pulled that RV and two others all over the continental USA (usually about 5 or 6 months a year, staying at each place one to three nights). There have been times when pulling the 37 foot, 15,000 pound rig that we’ve overheated going up mountains in Utah or Pennsylvania. Since upgrading to a 43-foot, 18,000-pound rig the overheating has becoming more common. No one ever taught me how to drive a turbo diesel and I thought it was like any other, but I was wrong.

By the way, I’ve added a pusher fan to the front of the radiator to push air in, hoping it would help. Two months ago I even added a secondary auxiliary cooling system to the radiator (haven’t been out with it yet to see how that will work).

For the past 10 years, when it starts to overheat, I would let off the accelerator and get it down to about 1,500 RPM to help it cool down. Wrong! I have been told that I’ve done more harm than good. Apparently, with a turbo diesel, the turbo kicks in about 2,200 RPM to help cool the engine. Reducing the RPM has done more harm than good, per a diesel mechanic.

Pass the word on if you think that I’m not the only ignorant one about turbo diesels. You may help someone else avoid overheating problems.



Chuck Woodbury
Chuck Woodbury
I'm the founder and publisher of I've been a writer and publisher for most of my adult life, and spent a total of at least a half-dozen years of that time traveling the USA and Canada in a motorhome.



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Joe Dobry (@guest_54835)
4 years ago

Too much trailer, not enough truck. Mr. Self does need some education about towing heavy with old trucks—turbo does not ‘kick in’ about 2200 rpms, it should be working any time acc pedal is pushed. What he thinks is the turbo ‘kicking in’ is most likely the fan clutch engaging to move more air. One comment about a 2007 diesel pickup hitched to a 43’ brick weighing 18000 not designed to do that is right on.
Get a new truck…..

Steve Thompson (@guest_10070)
6 years ago

If it’s a dodge I know my brothers had a water pump problem. The impeller was slipping on the shaft and it would over heat. He tack welded the impeller on the shaft and doesn’t have that problem any more. He tows heavy loads all the time too. Good kuck!

Bill Richardson (@guest_10053)
6 years ago

My thought is an engine oil cooler, You will increase your oil capacity and remove a lot of heat from the engine.

larry McGaugh (@guest_9960)
6 years ago

I had the same problem with my truck and found the problem to be a restriction on the inlet side of the turbo and bad design on the inlet air side of the air filter. feel free to send me an e-mail and i’ll go over the fix in detail with you.

Wayne (@guest_9712)
6 years ago

On my ’98 Dodge 5.9 24-Valve Cummins with automatic trans and 260,000 miles, I changed my original 3.55 rear axle to a 4:10, replaced the stock 3″ exhaust with an open 4″ , and replaced the stock injectors with 50+ hp RV injectors. Makes towing our 10,000 lb travel trailer much easier on the truck and now I’m not overheating and not exceeding my gcwr. Just points to ponder.

Roy Ellithorpe (@guest_9683)
6 years ago

You’ve had enough people tell you to keep your RPM up not down because lugging it creates more heat and running free creates less, as well as the fan runs faster.
BUT there are virtually NO diesel engines that have a NORMAL operating RPM of 2200 except possibly some small European car engines, which would pretty much negate the value of a turbo.
I would think that after 10 years your entire cooling system needs a Really good clean and flush, and make sure that your fan clutch is working.

Wayne (@guest_9663)
6 years ago

Clearly you’re overburdening the truck. Downshift on hills and slow down on the climb. It’s not a race to the top. And research water injection for diesel engines.

Ken (@guest_9656)
6 years ago

As far as I know there were not any one ton pickups that were rated to tow 18,000 pounds in 2007.

Ray Martin (@guest_9651)
6 years ago

It also could be a defective or lazy fan clutch that it ins’t engaging as much as it should to eng. temperature rise.

Seann Fox (@guest_9624)
6 years ago

Ever removed the rad and done an external wash out of the cooling fins? The rad packs up quite quickly on some highways this reduces the air flow through the fins and therefore the cooling

Dan (@guest_9616)
6 years ago

When climbing long steep grades, downshift your transmission to the next lower gear. Keep your engine rpm in 1800 to 2200 range. It relieves the load on the tranny, moved fluids through the system more quickly and will reduce the temps.

Jeff Kirk (@guest_9582)
6 years ago

Besides keeping your RPM’s up by downshifting turn off your dash AC. Instead run your generator and use your roof AC . If needed use a fan to help circulate the cool house air into the cab.

Alex (@guest_9581)
6 years ago

Since you seem to experience the overheating going up hill, please remember that your automatic transmission generates more heat when ascending hills AND that you’re likely moving slower. You’re putting more heat into the engine and transmission radiators, while less air flow dissipates less heat. You may notice that overheated RVs as well as those on fire are found at the top of hills; this is usually related to transmission overheating. Some pick up trucks are equipped with sensors to force downshifts or limit throttle if transmissions reach excessive heat levels. Those measures are intended to prevent transmission damage (and warranty claims!).
My suggestion would be to install an extra radiator dedicated to cooling transmission fluid before it reaches the stock radiator usually co located with the engine radiator. Also, install a transmission temperature gauge to monitor temperatures. If those measures aren’t as effective as you want, add a thermostatically controlled fan to the transmission cooler.

Brad (@guest_9578)
6 years ago


You haven’t specified what truck you’re driving or what temperatures you’re experiencing but, in general, you shouldn’t have any issues if the water temperature stays 240F or below assuming you’re using a 50/50 antifreeze/water mixture. My ’03 Dodge with a 5.9L engine has gotten as hot as 223F on long, steep grades without experiencing any problems. It is normal that the temperature will go up now that you’re towing a longer, heavier trailer. So change the antifreeze (and other fluids) according to the truck maker’s severe duty recommendations, do the recommended severe duty maintenance and you’ll be in good shape. Happy travels!

Chip Fisher (@guest_9498)
6 years ago

Please let me know what the tow vehicle is and I may be able to advise.
Enjoy the day.
BR, ChipFisher
Founder Blue Chip Diesel

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