Radiator & Cooling System

April 2, 2016

My reading on various RV’ing forums about the ’02 Journey with it’s Freightliner chassis had pointed out a weak part in the Freightliner cooling system that is subject to early failure. The Surge Tank is a pressurized tank that holds the overflow from a hot radiator. It is thick translucent plastic that develops cracks over time, either due to multiple episodes of overheating, from excess sunshine, or from the heat, chemicals, pressure (15 psi) it’s required to hold. No one seems to know for sure. Some have noted that it appears their tank crumbled from the inside out.

Generally, most owners have noticed during their pre-travel checks that the tank is weeping radiator fluid and limp home or to a shop to have the tank replaced. Some as many as 3 times over the years and +100K miles. And at a tank cost of $138 currently, plus labor. But the stories indicate that there is seldom a catastrophic failure of the tank. This is a good thing of course. If it’s weeping, you’ll generally find it before you travel when you do your pre-travel checks.

I think the part number is 05-17750-001 but there are few online pictures shown by tank suppliers so I’m not positive because without a picture, how can you tell?

What many others have done to replace their tanks when the inevitable happens is as follows:

  1. Buy new tank, along with speed nuts, and new hose clamps. Prepare for a 6 hour job. Tools needed are large flat screwdriver to remove hoses, heavy duty needle nose pliers, 9/16″ socket and ratchet, 9/16″ end wrench, and a Sawzall.
  2. Siphon the small amount of coolant from the tank.
  3. Using a Sawzall with 12″ blade, carefully cut the tank into 3 pieces, this allows access to the 4 bolts…2 of which are hidden on the passenger’s side, from the backside of the RV. (Or, two people can use a 24″ extension and wobble socket to access those hidden bolts from the top and bottom of the engine).
  4. From the bedroom access, number and remove the hoses from the tank. Mark the hose numbers on the old tank. Also mark the new tank with the hose numbers.
  5. Install tank using the bolts and speed nuts…which avoids having to use regular nuts and makes the job much easier for one person.
  6. Attach numbered hoses to numbered connections with new hose clamps.
  7. Replace coolant and test drive.

Here’s a link to a iRV2 thread about the job: Surge (Coolant) Tank Replacement

And here’s a link to pictures: Surge Tank Pictures

I wanted to get a handle on this early since I often spend months in the desert with bright sunshine and occasional hot stretches. I usually head north when it gets too hot, but there have been times where due to necessity, I’ve been caught driving in a heat wave. I wanted to be prepared while simultaneously being proactive about the tank. So I tried to track down the tank p/n and save that, then inspected the tank carefully as soon as I could and found that, yes, there were hundreds of tiny spider cracks in the visible portion of the tank I could access under the cover in the back of the RV. No weeping yet though.

If you look at the next picture carefully, you can see some of the cracks just above the center seam. There are many of them, but they seem to be just in that one section between the seam in the middle of the tank and the upper bend of the tank.

OLYMPUS DIGITAL CAMERAFirst thing I did was clean this side of the tank…and carefully inspect for any evidence of weeping. Finding none, I felt secure covering those cracks with a special waterproofing tape RV’ers usually repair their leaking roofs with. I thought it would help reduce the possibility of a large crack developing. And that product is Eternabond tape.

I have 6″ wide tape on hand, so I used cut pieces of that…a roll of 2″ would have made the job easier though. It stuck solidly to the side and molded nicely to the indentations. I left the ‘telltale’ uncovered on the right of the tank so I can still see how much fluid is inside…there weren’t any cracks in that area anyway. OLYMPUS DIGITAL CAMERA

I’m hoping that that stop gap measure gives me a couple years of use before I have to change the tank out. I also have to find a facility where I can spray my engine off soon. It’s really grungy. One small benefit of all that fine dust on the engine, and on the back of the surge tank, is that I would be able to tell if there is a tank crack back there that starts weeping. As you can see from this pic, no leaks on the backside…for now.OLYMPUS DIGITAL CAMERA

I have an idea of how to cover the exposed area of the tank to avoid sunshine and I’ll get to that next when I find the material I need. But for now with fingers crossed, I can head off across the desert with a tad less worry.

On Edit: Sept. 2016

Still no leaks from my temporary fix using the Eternabond tape. But I’ve only put a couple thousand miles on it.

On Edit: July 2017

I made a friend in San Felipe, Mexico early this year, and she has a ’04 Journey with FL chassis. Her surge tank was in much worse shape than mine. I could push my thumbnail into the rotten part on hers, it was crumbling. I could see it was also crumbling inside. Spider cracks everywhere, but no evidence of weeping fluid. She should have replaced it there in Mexico, but she wanted to get the job done up in Vermont where her favorite shop is. So I did the EBond treatment to her tank before she left Mexico. I’m happy to report that the tank made it all the way up to Vermont from Baja without issue. She had the tank replaced soon after she got up there to her stomping grounds while they worked on other chassis issues so I’ll never know how long the treatment might have lasted.

I’m probably pushing my luck, but I inspect my tank regularly and I’m still not seeing any weeping from the cracks my tank developed. And my tank isn’t visibly crumbling like my friends. So I’m still putting off the job of replacing it for a bit longer. I am beginning to think that the Ebond tape I put on helps both seal and prevent sun damage, and then the fact that I’m very cautious about not overheating the engine…always downshifting when climbing hills so the temp needle on the gage doesn’t climb much…helps keep the coolant from overheating and contributing to the cracking or deterioration from the inside. But that’s just speculation on my part.


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