Possible wet cylinder cavitation pitting from poor coolant?

[Aurum]

We are still in the inspection phase of possibly purchasing an 04' motorhome with a Cummins ISL 400hp diesel with 71k miles. So far we've only received the coolant analysis results. The tests show that the engine coolant was in poor condition if the coolant was originally a conventional low silicate Ethylene/Glycol formula as opposed to an ELC Extended Life Coolants which are nitrate based. The results below show a low level of nitrates which could indicate it may have been changed to a ELC, but the other numbers seem more consistent with a conventional E/G coolant. It also possible it is a mix of conventional and ELC which isn't advised.

On a 0-4 scale with 4 being critical, the overall score was 3. The following are the abnormal results.
Basic testing:
-Color- cloudy dark yellow.
-7.4 ph, (normal- 8-11)
-Nitrate 295 ppm -strip test (normal 800-1200)?
-SCA level 0.6 (normal 1.2 -3 .1)
-Corrosion metals: Copper 13ppm
-Corrosion Inhibitors: Molybdenum 76ppm (normal 1000)?
Everything else was within normal levels.

I've read about how important it is to maintain the coolant condition and SCAs in diesel engines with wet cylinder sleeves due to the possible cylinder pitting from cavitation due to poor coolant which could lead to pinhole formation. Don't know if this is true, but I was told by a service manager that Cat motors were more prone to the pitting than Cummins.

Am I being unduly concerned about the condition of the coolant which might have the potential to cause severe failure?
Of the repair/maintenance invoices reviewed, none show radiator/coolant maintenance so I'm guessing there's a good chance the coolant is the original factory coolant.

A Spartan factory tech advised that the original coolant was an Ethylene/Glycol 50/50 mix. He also said Spartan advises to continue using the same original type of coolant whereas a Cummins factory tech said they like the newer OAT coolants but that either was OK. He also said that the freeze plugs can start leaking from corrosion which can be an indicator of poorly maintained coolant.

This will be our first motorhome purchase and this particular coach has several features that we really like but after not having a chance to test the old oil then receiving the poor coolant tests results we are questioning going forward. Though

Would like to hear from someone that has dealt with this same issue or knows of someone who has.

[GaryKD]

Hi Aurum,
I have not dealt with this issue. For me, I'd pass on this coach. If you do make a purchase, when the coolant is replaced, make sure the rubber connecting hoses are also replaced. I think there are 5 of these connecting hoses. They are about 8" long and connect the coolant pipes to what ever they are connected to.

[RinkersRanch]

RV Diesel engine coolant article. Here is a link to a great article on the subject. I use to teach Diesel engine maintenance for Caterpillar and this article touches all the important bases on Diesel engine coolant requirements. No, it will not answer the question 'should I buy this coach' but it will explain what is going on in the cooling system and what is required of coolant.

[Steve Ownby]

Originally Posted by Aurum

We are still in the inspection phase of possibly purchasing an 04' motorhome with a Cummins ISL 400hp diesel with 71k miles. So far we've only received the coolant analysis results. The tests show that the engine coolant was in poor condition if the coolant was originally a conventional low silicate Ethylene/Glycol formula as opposed to an ELC Extended Life Coolants which are nitrate based. The results below show a low level of nitrates which could indicate it may have been changed to a ELC, but the other numbers seem more consistent with a conventional E/G coolant. It also possible it is a mix of conventional and ELC which isn't advised.

On a 0-4 scale with 4 being critical, the overall score was 3. The following are the abnormal results.
Basic testing:
-Color- cloudy dark yellow.
-7.4 ph, (normal- 8-11)
-Nitrate 295 ppm -strip test (normal 800-1200)?
-SCA level 0.6 (normal 1.2 -3 .1)
-Corrosion metals: Copper 13ppm
-Corrosion Inhibitors: Molybdenum 76ppm (normal 1000)?
Everything else was within normal levels.

I've read about how important it is to maintain the coolant condition and SCAs in diesel engines with wet cylinder sleeves due to the possible cylinder pitting from cavitation due to poor coolant which could lead to pinhole formation. Don't know if this is true, but I was told by a service manager that Cat motors were more prone to the pitting than Cummins.

Am I being unduly concerned about the condition of the coolant which might have the potential to cause severe failure?
Of the repair/maintenance invoices reviewed, none show radiator/coolant maintenance so I'm guessing there's a good chance the coolant is the original factory coolant.

A Spartan factory tech advised that the original coolant was an Ethylene/Glycol 50/50 mix. He also said Spartan advises to continue using the same original type of coolant whereas a Cummins factory tech said they like the newer OAT coolants but that either was OK. He also said that the freeze plugs can start leaking from corrosion which can be an indicator of poorly maintained coolant.

This will be our first motorhome purchase and this particular coach has several features that we really like but after not having a chance to test the old oil then receiving the poor coolant tests results we are questioning going forward. Though

Would like to hear from someone that has dealt with this same issue or knows of someone who has.

I applaud your self education concerning the critical importance of coolant particularly in a wet sleeved diesel. Most buyers are not nearly so knowledgeable.

If it were me I would pass on this one. The coolant may be an indicator of cavitation damage but it's also an indicator of an owner who did not keep up with the maintenance. I'll bet the transmission fluid and filters are OEM also. There are plenty of very well maintained coaches on the market. Keep looking.

The C7 or 3126 Cat which is most often found in motorhomes is not a wet sleeved engine and is not subject to cavitation.


Steve Ownby
Full time since '07

[Dtwallace]

Aurum,

Not disagreeing at all with GaryKD's caution. How ever I'd like to just add my experience in operating wet sleeve engines in over the road trucking.

In my opinion, and experience, it would be the milage put on that engine during the time the antifreeze in question was in it.

With setting time, not running time, corrosion would occur without the proper protection. However it would take quite a long time to cause damage as it would be more like a surface rust on the block and cylinder liners, in any at all.

Continued operation in that deficient antifreeze condition wound cause a failure of the liners at about the 500K mile area if it was a really bad mix.

The new engines are so robust, that I'd would not be concerned with a low mileage encounter with bad antifreeze where the rest of the engine tests out in perfect working order.

The obvious concern is how you will care for this engine through out it's remaining years.

Suggestions above to replace rubber hoses or other items is cheap insurance against future failure, and you know exactly what you are working with. To go farther, at 71K, for peace of mind go ahead and replace all the drive belts also. Chances are then, you'll never have to replace them again, unless you are never planning to sell this coach. Just my thoughts. Finding the perfect coach is all but impossible. Finding one that you can and are willing to work out minor issues is the start of an adventure.
Best of luck
DTW

[Hooligan]

It does sound like a mix of coolants.??? Agree with Steve above, good homework.....
Cummins may be the one to ask about the results of the testing
Here is the Cummins Service Bulletin on Coolants. http://www.granlydiesel.com/fileadmi...2__12sep13.pdf

[Aurum]

Thanks guys!!!!! Great info! I have more reading/learning to do. I'll update as I find out more. Had I been able to sample the old oil I think I'd have a better idea as to what the best decision would be but I can only go on with what I have.