Transmission overheating

[Marty and Suzie Schenck]

I too would like to isolate the 2 cooling units from each other. I spoke to an Allison dealer in Auburn Wa. (US Transmission) and he says the 3000 maybe but not the 4000.  He said the heavy duty 4000 really needs the engine coolant to get the trans up to temp and then because of the torque of the higher horsepower engines it still needs the engine coolant to keep it at the cooler temps. He also said that an isolated cooler would keep the trans at a too cool temp or not cool enough. I'm trying to find someone at Allison headquarters to answer this question but have not had any luck. I'm also going to ask the transportation dept. of the school district that I work for if they can get me a phone number for Allison. Marty

[Robert Mathis]

Tim, what was th mileage when your cooler failed? I am going to look at mine and see if it's the same type unit. I have had oil coolers fail before on my boats, but that was caused by salt water corrosion in one case and an "O" ring failure in the second case. One of my best friends just spent over $60,000 to rebuild two CAT marine diesels because of failures of his H20 cooled intercoolers which allowed water to be drawn into the air intake system. Unfortunately for him, he was about 100 hours out of his extended warranty. I was lucky both times mine failed, since I noticed waterin the oil on the first one and had a catastrophic oil pressure failure on the second, but was doing some testing and was watching my guages when it happened.

[Gerald Farris]

Jeremy,
All Beaver coaches have a liquid to liquid transmission cooler. There are several reasons for the liquid to liquid cooler. First it is more efficient than an air cooler. The next reason is that it will keep the transmission at operating temperature regardless of the outside temperature. An air cooler that is large enough to adequately cool you transmission in hot weather, will over-cool your transmission in cold weather and drop the transmission below operating temperature. It is almost as bad for your transmission to be continuously operated at a low temperature as it is for it to be operated at a temperature than is to high. For these reasons the liquid to liquid heat exchanger is best because it will keep the transmission at the proper temperature in all weather.

As for changing the liquid to liquid cooler for preventive maintenance, that is hard to justify. The number of coolers that fail is so low that the cost of a new cooler in the thousand dollar range when you consider labor and parts (cooler, TranSynd, and coolant), can not be justified. The best thing that you can do as preventive maintenance for your transmission cooler in my opinion is to keep track of the PH level in your coolant, and change your coolant if it starts to become acidic.  That will prolong the life of your entire cooling system including your transmission cooler. However some coolers will fail from metal fatigue, but low mileage ones fail almost as often as high mileage ones from my experience when it comes to metal fatigue.

Gerald            

[Edward Buker]

I for one do not know the faiure rate of the water to oil units that were used in our coach. Certainly the failure mode, wether it be vibration related, corrosion related, thermal cycle related is not clear. In my conversation with Pacific Power Products they were concerned enough to proactively replace some units before failure. How effective this is and the timing of replacement would normally be related to the cause of faiure and how each of our units is used in real life. With most failure modes one size does not fit all.

What probably makes the most sense is to learn what we can and each of us make decisons based on what is shared. Nobody will know more about these units and the expected life than Rocor. Some questions come come to mind.Why do these coolers fail?  Does Rocor have a more durable design that has demonstrated a significantly lower failure rate? Also based on the predominant failure mode has the unit used in our coaches been redesigned to be more durable and if so when?

On the oil cooler page there are several designs for oil to water coolers. The one at the top appears to be pretty robust and has a removable core which begs the question, does that core have a defined useful life and a recommended change frquency or is that to facilitate cleaning if the need arises? Why this design?

http://www.rocore.com/products.html

Regarding Gerald's comment on metal fatigue with low mileage units failing almost as often as high mileage units, that certainly can be true. If these are internally soldered units, how much solder is in the joint, how well all the surfaces were cleaned and fluxed, the temperature applied and if it caused brittle metallurgy. When soldering, these issues cause defects that will fail somewhat randomly over time just as Gerald observed. The other side of the coin, the one we would want to be sure does not exist, is a design issue where we are getting wearout of these coolers within the normal use life of the coach. That would be a high failure rate, without defects being involved, due to an inadequate design. If that is what we have we would need to know that and make some decisions.

 Tim, if you could provide the PN for what was removed I will try and have a conversation with Rocor. What they will share may be a different story. It won't hurt to try and learn what we can. Given the high cost and the lengthy repair to replace the transmission, we would want to know if these coolers experience wearout. If it is random defects only and the cooler normally lasts multiple lifes of the coach then it is just the luck of the draw if you get a defective one and changing one preventatively would not likely improve your odds.

Later Ed

[Steve Huber Co-Admin]

Ed,
If I understand your post correctly, it sounds like the failure occurs at a solder joint. Assuming the cooler was not subjected to extreme operating conditions, this seems to indicate a defect related, rather than intrinsic problem. Thus, the projected failure rate would be difficult to determine unless one knew more about how the defect was introduced; e.g. batch of solder, given manufacturing line, specific period of manufacture, etc.. From the inputs on this thread, it doesn't sound like this problem has impacted many coach owners. Obviously engine hours, operating conditions on any failed units would help to determine future risk.
Steve

[Jeremy Parrett]

Gerald,
   thank you for your reply. I also see the Rocor design on their webpage that has a removable "bundle" of coolant tubes. My Yanmar engine has a very similar arrangement for the seawater cooled sealed cooling system.
Next time I change the Transynd I am going to install the Rocor intercooler with the removable tubing bundle.
The tubing  could be changed at a set mileage and hopefully eliminate the possibility of a failure.

[Edward Buker]

Steve and Jeramy,

I think what we have is defect related and the extent and nature of the individual defect in a particular cooler will dictate when it would fail. The issue is we do not know for sure if we have what is refered to as a defect fail mode or a wearout fail mode in the design of the coolers. If defect mode and you replace it you may be taking a good cooler and replacing it with one with a defect in it. If we have a wearout mechanism (like a filament in a bulb has a predicatble life in hours or a tire based on tread wear and miles) then we have a need to look at the expected life of the cooler and change one before it fails. We do not have any failure insight yet, so it is too early to understand if any change of the cooler would be expected to provide a benefit.

Later Ed

[Tim Bentley Co-Admin]

The coach had 140000 miles on it when the cooler failed.  I do not know the pin, but it was a Rocore shell and tube cooler # 3-1249T, built around 2002.  For the first 75000 miles the radiator had regular coolant which was than changed to longs life coolant for the reminder of the miles.  The PH was checked often and was never found to be off.  There was a chemical canister in the system to help maintain the proper balance, the canister was removed with the change to the long life coolant.  The radiator has had a small leak for most of its life, I needed to ad a gallon of coolant about every 5000 miles.  

If I am not mistaken Mike Collins also lost a transmission from a water leak, don't know if it was the cooler or not.  

The cost of replacing the cooler would be around $900.00  + labor.  

[Edward Buker]

Thanks for the Model info Tim. With a few calls into Racore I have reached a source who spent 20 years with Allison followed by being the rep for Rocore in the transmission cooling field. He (Dave Wheatley) had a lot of information and I will try and pass the info I gathered along.

The 1249T cooler has been around awhile and was originally designed by Stewart Warner. It is what is known as a fixed bundle design and that style is still made today. It is a set of tubes silver brazed into a brass end cap and I believe that is brazed into a steel shell. They have a wear out life that is hard to predict individually given it is a function of use conditions but they do wear out. He discussed a 5 year life but we both acknowledged that our application is not as severe mileage wise or thermal cycle wise as many. The issue with not considering a preventative change is the cost of a transmission vs the cost of a cooler. He highlighted that the actuarial tables for rebuilt Allison transmissions do not match the normal life of original units. If you can prevent this type fail your original will likely outlast a rebuilt and your coach. FYI, the original cooler was warrantied for 18 months or 100k miles which probably does not give us much insight into the useful life.

These coolers have two primary failure modes that can occur. Corrosion is one possibility. I indicated that most of us use ELC coolant and Transynd and he said that we are using the latest state of the art chemistry with very low corrosion rates, so lets consider that one a non issue. If you are using the non ELC coolant check your PH and keep it optimized with additives.

The second failure mode is thermal fatigue causing a crack. On start up the engine coolant and transmission coolant rise at different rates and as the thermostat opens and closes there is some thermal shock that is involved. The tubes must expand and contract from ambient to maybe the 220 degree range of fluids and that stresses the tube bundle. If you have a retarder, and luckily we do not, that adds an increase component of stress due to higher temperature excursions. So we have the temperature excursions of normal travel and those due to desert travel and mountain pass climbing, again all individual driving habits and travel patterns. Prediction of useful life is hard but he was clearly concerned about a tube crack due to thermal fatigue in the shell at some point. The life of the unit depends on your use and probably the best guidance we could get would be data from failures in multiple coaches (Tim has one data point). If anyone knows mileage and age of several more we may be able to use that info to come up with some logical mileage and age value to guide us. This all assumes that we do not have an early fail due to a defect in the cooler build and I would guess that we are all pretty much beyond that at this stage.

There is a better cooler design that has evolved to eliminate the thermal fatigue fail that he would recommend. There is a floating bundle design and he thought that if that design was used, he was comfortable that in our application it would last the life of the coach given that corrosion was not an issue and that the floating bundle design does not suffer the thermal fatigue failure mode. The bundle expands and contracts without restriction.

The issue is that there is not an exact bolt in conversion. He will provide us recommendations along with drawings and insight into the differences that would have to be allowed for in a conversion. They are not that major but fittings and mounting may have to have some alteration. He indicated that the thermal performance would be equal to or better for this cooler over the 1249T design. He would get to this when he returns after the 1st of the year and I will pass the info along. Maybe Gerald or anyone else into the mechanics of these things could offer up an opinion as to what would be needed to physically change over and not worry about this issue again.  We will take our time and see if some logical path evolves...

Tim, I'm sorry that you are suffering through this issue. Hopefully you can find a way to have a good Christmas after all.

Later Ed

[Jeremy Parrett]

Ed and Gerald,
  So we will wait till the New Year to find out all the details of the new "floating bundle" design.
  I have a Ford F250SD 4x4 6.0 diesel  with one of these liquid to liquid coolers.The previous owner had a mega $$$ bill when the cooler failed at 45,000 miles !!     I know the cooler has 80,000 miles on it so I am inclined to change it out for a new floatng bundle design as well as the one on my Marquis.    

[Marty and Suzie Schenck]

Ed, Thank you for all the information and your time spent researching it. I also spoke to Pacific Power here in Kent, Wa. and they also said that changing to an air to liquid cooler was not possible for the 4000 (same as US Transmission said). They went on to say that they are recommending and are changing out coolers on firetrucks every 2-5 years depending on make and model. I'm really wondering if (in my case) I should just change it out with something newer and better to be on the safe side. Please do keep us updated.
Marty

[Edward Buker]

Marty,

I would hate to spend the money too early if it is not really necessary. What we need is some data of mileage and age for failed coolers of this type in Monaco RVs. Short of that we would have to get an educated guess from Rocore. They may have an RV cooler fail database. Tim mentioned Mike Collins, if somene knows him and could get that info, maybe that would be another datapoint.

The fire truck would have no warm up time, hard relatively short runs, and then it would be shut down again. For the miles traveled thay would have many more thermal cycles then a typical RVer having the same mileage. They also need to get to the fire and be available so they would conservatively be trying to prevent major failures while in service. 2 to 5 years seems conservative for RV folks but only the fail data will give us the best answer. I would wait and see what info comes our way in January.

If you do go ahead and replace one of the current designs with the same PN and design I would say you would be reasonably safe for the next 5 years and 100k miles. If there were a lot of RV transmission cooler fails within that range I think we would have had more bad news on the forum.

Later Ed

[Tim Bentley Co-Admin]

Just got the coach back from Valley Power Systems and all seems to be well.  We were very happy with their service and would recommend them to anyone needed Transmission work in the San Diego Area.  They seem to be a well respected company, they were doing service work on fire trucks from as far away as Los Angeles.

I did pick up some more useful information while talking to the service manager.  He said that the cooler on our coach was a very tight fit,  installing another unit that was of a different size and shape would be a problem.  He also said that 80% of the transmission failures they fix are caused from water in the fluid.  It only takes 2% water to destroy a transmission.  The cooling system sure seams like the weak link in the system.

[Edward Buker]

Tim, Glad you are back on the road before Christmas, that must feel good. Thanks for passing along the insight regarding space constraints and the transmission fail service managers observations. It does look like there is a common theme on that subject emerging from multiple sources. 8 out of 10 fails having a common source would warrant taking the root cause seriously.

For all Patriot and Marquis owners with C12s please send your coaches year and miles to me at ednjillb@hotmail.com if you have not had a fail. Just approximate K miles would be fine.  If you have had a cooler fail or know of someone who has please let me know and send me the approximate miles and age when the fail occured.

If someone else owns a Monaco product that has a C12 drivetrain and you would like to pass your info along, that would be welcome also. Both a fail database and a database of still good coolers in the field may be useful in coming up with some life expectations. We will see what we can learn to help ourselves. Everyone have a good Christmas.

Regards Ed

[Edward Buker]

For all Patriot and Marquis owners with C12s please send your coaches year and miles to me at ednjillb@hotmail.com if you have not had a fail. Just approximate K miles would be fine.  If you have had a cooler fail or know of someone who has please let me know and send me the approximate miles and age when the fail occured.

FYI, I have the data for five coaches so far. Hoping for more inputs in the next week or so. At some point I will tally up for the forum the miles, and age of any fails as well as the same data for coaches without fails to see if it will help us in any way.

Later Ed