We just found out that our CAC has a nice long crack in it. Has anyone had this problem and do you know where to look for a replacement?
It can almost certainly be repaired by a competent welder using the Tig, also known as Heliarc process. Others have repaired them with epoxy products. If you're anywhere close to Corpus Christi Tx I can recommend someone with lots of experience to weld. Be sure to clean it thoroughly inside and out before reinstalling.
Echo Chuck. Running a bead to fix it should run under an hour shop time and they may be able to reinforce the spot where the crack originated and prevent any future cracking. In other words, better than new. A good shop that routinely does intercoolers may be able to tank it, clean it and put dust caps on so it's ready for re-installation. A call to a hot rod/racing shop will locate the right welding shop quickly.
Chuck's recommended shop would be good if in your vicinity.
Epoxy would work as a DIY fix but TIG welding is the way to go here.
Pierce
There's a 6 week lead time. The company is located in Corpus Christi TX. Do a search for Atlas Radiator.
6 years ago it was around $1500.00 including shipping. Is the crack in a location where it could be soldered or epoxy'ed? I would see if it could be repaired first
Our location is in AR, the trouble was diagnosised in Omaha, NE another excellent Cummins shop, not like our local Little Rock Cummins. We tried the epoxy thing and tried to nurse it home. But the Boston Ozark Mountains was tough, but got home. Called Corpus Christi and waiting for a call back. Foretravel is suppose to have 2 of them but they had to call someone else to see if it was the right one for our model. :-\ Our local good friend mechanic said he would do it for us. We will weld it if it is repairable and keep the old one for a spare. Thanks for everyone's input! ^.^d
OK I do know about this type of repair as have done it successfully.
You cannot weld it according to my very expert alum'n welder (this is all he does in life) He refused to do mine as he said the carbon that has been left over inside will cause the tig to burn up and make the problem worse. He absolutely refused to waste his and my time.
I contacted the Company in Corpus Christi and they said ,no problem it is around $1500 but they had none in stock and needed 6 weeks to cast. I contacted FoT and they said 6 weeks and $3300,00 !!
I washed it out and cleaned up the cracks and used Devcon 2 part Plastic steel # 10240. It has held up great and I pressure tested it to 45 lbs pressure and it held no problem for 12 hrs (I did not bother any longer) This was 16 months ago and looks as good as new. I called Devcon about it and was assured it would work. They make an Aluminum one that should be better but it was not available locally so I used steel. Easy fix and way cheaper. You have to remove it from coach to fix as you need to wash it out. If you post a good picture of it I will let you know what I think as it seems I am the only one so far to fix the CAC this way. All others have replaced it. Everyone told me not to do what I did and it has been fine. I run up to 34lbs boost many times--no problemas.
JohnH
I had a CAC failure on my 2007 Nimbus. Let me tel you that we had an 18 crack along the seam. I had it TIG welded and it lasted all but a year. Then, I had Foretravel ship me out a new CAC. The new one was constructed differently. First, the two sides of the CAC was steel instead of aluminum. Next, there were three steel rods on the outside of the aluminum frame connecting the two steel ends. Even with these changes, the unit fit. There is tremendous pressure in these CAC units. Was like running down the road with a giant leaf blower on the passenger side! What a large create to ship. We used Freightliner in Las Vegas to do the job. Great, Great service!
I could tell originally that the CAC went out because I lost the boost pressure. Yes, I have a Silverleaf where I could read boost pressure. Also, I had a large noise which I could here when going under a bridge. When I was driving trucks, this was a common issue since the grill is mounted upfront. Since I replaced the unit, what a difference.
We just had an exhaust manifold crack and recently had that replaced as well. Normal, over the road stuff.
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This is a limp along suggestion - when I had my CAC out awaiting replacement, we fabbed up a bypass pipe and it drove fine (93 U280 w/banks)... I wouldn't go on a major trip that way, but it will work. Oh, and the Banks didn't cause it - but it did help me find it! In my case it was a poorly constructed CAC that was two intercoolers butt welded together.with aluminum plate end caps. Back then they were source out of Sacramento.
I have put over 12000 miles on mine since I repaired it and the fix looks the same today as when I did it. 25 to 30 lbs pressure is not a lot only the volume is large. Pressure is the main factor.
As Dave say's "do what makes you warm and fuzzy" but I do not like throwing money away and this product has been used for many years to repair castings of all kinds
John H
Let's see here...say the cac is six square feet. That's 864 square inches X 28psi = 24,192 LBS of force trying to blow the intercooler apart. (simplified, approximate calculation) There's a lot of stress and resulting strain on these things, that's how they manage to split a welded joint apart. Unlike steel, an aluminum weld is always going to be weaker than the parent metal and in addition there is a heat affected zone around the weld which is also weaker. Comparing strength of materials might lead you to choose steel over aluminum, thicker aluminum but probably not epoxy.
I agree with you Chuck, there is a lot of pressure in the CAC. I see my boost pressure on the Silverleaf go as high as 32 psi climbing steep hills. When I replaced my CAC, the new one had two steel ends and the middle made out of aluminum. I would think the aluminum would dissipate heat better while the steel end offer strength. In addition, the two steel ends with aluminum in the middle had two steel rod connected at either end so it sandwiched the aluminum core in-between. These rods are on the top and bottom of the aluminum inner core, leaving the face of the aluminum core open for air.
Sounds like they've improved the design significantly with the steel caps and bolts. I'd like to take a shot at modding an original aluminum cooler. If anyone has a failed one they would be willing to part with I would like to buy it. I've got CNC machinery to cut new parts, TIG and MIG including pulse+pulse mig to weld. This is an expensive part that several folks have had fail and I'd like to see if it can be beefed up. I love this kind of stuff...
I am not an engineer or even a good mathmatician but have a little problem with some of these calculations.
If the unit is open at both ends how does the CAC build up that kind of pressure Chuck?? When mine was leaking there was no way in H--- that "blow by" was anything more than air coming out of my compressor gun when blowing off something?? I do not see the cooling "fins" taking any more than a 100 or so lbs, as those figures quoted seem crazy to me :o
Believe me or not mine is fine and saved me 2 or 3 coach bucks, and, at the same time I framed the rad and CAC around with belting to create a tunnel for directing air thru' them and not the road crap. I like to fix things right and not throw money away, but if you have lots of it I guess some people do not mind doing that!
Barry L has seen my repair and had positive comments on it.
John H
Intercoolers only see 30-40 psi max. Compare this to RV fridges at about 400 psi. Any failures are not pressure related but due to flexing, vibration, etc. Aluminum does not like to constantly bend and will crack. I expect the majority of failures are from stress from the hoses due to engine torque and also to the mounts, in other words poor mounting design or poor intercooler construction. Correctly designed and mounted, an intercooler should last forever.
Any "blow off" is due to the system having a waste gate. Waste gates are used so a turbocharger can build pressure at a lower rpm so the engine develops more power sooner. As soon as the maximum pressure the waste gate is set for is reached, it opens releasing excess pressure so the engine is not damaged. This has nothing to do with intercooler construction.
Not all turbocharged engines have intercoolers and not all have waste gates. Just depends on the application the engine manufacture designed it for.
Here is a chart listing intake pressures for the 5.9 Cummins as installed in a Dodge Ram PU:
Ram Diesel Turbocharger Specifications (stock engine)
Year Engine Rating Max Boost Range Wastegate Holset
Turbocharger Turbine Housing
(sq cm)
89-90 160 HP 22-25 psi 22 psi H1C 18
91-92.5 160 HP 15-19 psi 17 psi H1C 21
92.5-93 160 HP (CPL 1579) 18-21 psi 19 psi H1C 18
94 160, 175 HP 15-18 psi 17 psi WH1C 12
94 160, 175 HP 15-18 psi 17 psi HX35W 12
95-98 160, 175, 180 HP 15-18 psi 17 psi HX35W 12
96-98 215 HP 21-23 psi 23 psi HX35W 12
98-00 ETC 215, 235 HP 18-20 psi 20.8 psi HX35W 12
01 ETC 235 HP Auto
and Manual 20.5 psi 23 psi HY35W 9 single port
01 ETC 235 HP Manual 20.5 psi 23 psi HX35W 12
01 ETH 245 HP 20.5 psi 26 psi HX35W 12
Pierce
I stand corrected on the pressure issue as JD has emailed me on it. I have finally been wrong on something in my life- :P :P ^.^d
John H
First of all let me say this, John. I salute you on your repair, I think it's a fine example of problem solving using available technology. It obviously worked for you and may work for others as well.
As Pierce says, these failures are most likely due to stress cracking. I suspect the cracking is caused by the cooler expanding and contracting due to heat and pressure cycling. Aluminum, unlike wood and some composites has a finite number of bending cycles it can go through. Exceed this and it will crack. Restrain it from bending and it won't.
As far as the calculations go, using 28psi as a max pressure seems valid, I think most Banks equipped engines will develop this but dropping it to 20 psi still yields some pretty extreme pressure on the device. While it's true that it's open at both ends, one end has a pump hooked to it and the other end is restricted by the mostly closed valves of the engine and pressure in a closed system is distributed evenly. Without knowing the total surface area of the cooling chambers it's impossible to calculate exactly what the total force is but the collector and exit chambers will be subject to some extreme pressures due to the large surface area of these chambers. I suspect but don't know that the cracks are typically in this area rather than the cooling tubes.
I'm always amazed at the way it adds up. That's also the reason welded aluminum marine fuel tanks are pressure tested at 3 psi or less. Even with welded baffles inside they are bulging like sausages at 3 lbs. That's because a 2' X 2' X 8' tank has 31,104 LBS of force distributed inside at a pressure of 3 psi. That's how 100 psi exerted on six one square foot or less patches will support a 30000 lb coach down the road and 40 psi on these same patches will lift it.
Enough from me on this, I'm sure most folks find this both boring and irrelevant. I'm fascinated by it but then my heroes are all engineers.
Gee thanks, Chuck. Blush ;o)
I didn't know you cared.
...Hmmm... But then maybe he meant to say: "Enough from me on this, I'm sure most folks find this both boring and irrelevant. I'm fascinated by it but then all my heroes are engineers."
best, paul
The 3 holes in my cooling fins were about 1/8" x 1" long and caused by loose bolts holding the fuel cooler banging against it for a couple of years. I did not even know it when I bought it and do not think the previous owner did. It was not stress related at all.
John H
Made a quick run to Nac, got our new CAC, was looking at pictures on Barry's site (Thank goodness for Barry and the forum) There looks to be a lot of difference between Barry' s 03 and Steve & Anna Lindemann's 07 . Barry was replacing his radiator and Steve's CAC looked like it was in with the radiator(one big unit)?? We are having a local mechanic do ours , (Foretravel couldn't get to us until mid June ) and we would like it done before then. So if anyone has any pictures or advice so we can tell the mechanic it would be helpful.
Now, some bad news , the creeping in slide is back. The fix from HWH only lasted a week; back to HWH??? Not sure waiting on them to call us back.
If not for all this help , David said he would get out of RVing sit on the front porch and just wave at all the cars going by, the only thing is we live in the last house on a dead end street :P
On my 2007 Nimbus, Freightliner was able to drop down the entire unit which included the CAC and radiator. What was impressive was how they did the repair. The mechanics put the entire RV on a lift and raised it off the ground. Then, using a transmission jack raised to under the entire CAC unit, they unbolted it and lowered it to the ground. This is one way Foretravel could not do it since there are no lifts at the repaair bays on Nacog. The entire repair was done in three hours. We ordered the CAC from Mike in repairs, paid the trucking cost, and under extended warranty had the work done. This was in Las Vegas, NV. I am sure any Freightliner shop could do the same work.
Thanks! ^.^d