changing engine antifreeze C7

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Iron Horse

Well-known member
Feb 28, 2009
Chesterfield, Virginia
I am in the process of changing the antifreeze in my Cat C7 as it is seven years old. I have a Winnebago Journey 36G. It has Alliance ELC precharged antifreeze in it now. I wanted concentrated fluid so I could mix the fluid my self but they said all that was available was 50/50 mix, so I went to Caterpillar for the ELC precharged concentrate and they told me that 50/50 was all that was available. My problem is that I have drained the radiator, cab heater lines and the hot water heater compartments (it heats the camper water thru a heat exchanger below the radiator) and flushed it three times and am still getting orange contaminated water
out.  My question is, there must be areas in the water jacket that do not drain, so if I add 50/50 its going to be diluted with this and therefore not 50/50. Am I doing something wrong? Your opinions appreciated.
Little Bill
Bill, here is pretty much how I have been changing coolant for a long time. This applies to diesels but specifically for our style rigs with the motor aid etc. I wasn?t sure what type of coolant was used in my MH when I purchased it but I wanted to make sure I got it all out so I could use ELC. Most of the ELC brands are good for 6 yrs as long as you put in a can of extender after 3 yrs. If you want Cat ELC concentrate then call up the local Cat dealer parts dept and ask for the concentrate part #238-8647. It was app $23/gal here so I used Detroit Diesel Powercool Plus ELC. The Detroit concentrate is part #23519397 and was app $12.50/gal. I?ve used it for a number of yrs in diesels so no problem there. Don?t forget to get the extender, you?ll need about a pint. Also don?t forget to get distilled water from the grocery store to mix with the concentrate, it?s only about a $1 per gallon.
If you have a C7 your rig is probably an 04 or 05 so should be similar to mine. I have the motor aid also and had app 8 gals in the cooling system if I recall. I always catch the fluid in a marked container so I know how much was in the system. (I use a 30 gal barrel cut in half) This helps you to know that you have most of the air removed from the system when you finish. Under your drivers side frame rail below the engine you will see the 2 ea. 5/8 hoses that will run up front to your heater. At this location they will have drain valves in them and this is the lowest point in the system so drain it here and then close the valves. You don?t need to unhook any other lines. Go up front and find your heater core hoses, 2 ea 5/8?. Right where the one connects to your heater valve, unhook it and add a splice with the T-fitting to install a flush fitting like you do on a car/truck. Hook up your garden hose, Install the spout on the radiator and you are ready to flush the system. Turn your hose on slow, you can easily over pressurize your cooling system if you get impatient. It will take a few minutes to fill the system and start flowing out but as long as you have flow out of the top of the radiator you are good. When it runs clear shut off the water, open the low point drain valves again and remove all the flush hardware and reconnect the heater hoses etc.
The hardest part of doing this job is getting all the air bled out of the system so you don?t end up with a hot spot. Take your time filling the radiator, go slow when pouring in the coolant. I don?t remember what it is but Cat actually has a spec to follow for how long it should take to put in a gallon of coolant. Just don?t be in a rush and you will be fine, this will allow air to come out as you pour in the coolant. Once you fill the radiator and it won?t take any more after sitting a while then go in and start the engine with the radiator cap REMOVED. This part is pretty important. Run it at 1500 rpm +- for about 3 minutes, then come down to idle for 1-2 minutes and shut if off. Wait a few minutes and top off the radiator and do this procedure once more. Then close up the system and warm it up to oper temp, let it cool and check the level in your expansion tank again. You should have added app the same amount as you drained.
Now would also be a good time to change your rad cap, run about $8 for a 13 psi cap, bring it wih you to the dealer when you get the coolant. Sorry for the length but hope it helps.


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Mavarick, I really appreciate your reply to my question. I really want to put the Cat ELC precharged antifreeze into the system if I can locate the concentrate. There are five places here in Richmond Va. that may have it and I'll check tomorrow. I even have a part #238-8647.  I drained approx. 8 gals out of the radiator and I think it still has about three gallons in the system. I think if I flush until it runs clear and do a final flush with distilled water it will have three gallons of distilled water in it, to which I will add three gallons of Cat ELC precharged concentrate it will be 50/50 mix. I will then add the remainder of 50/50 mix to top it off. This will give the correct freeze protection and Supplemental Coolant Additives, which should be good for another 5 years. Do you think this would be OK? We used the Detroit Diesel antifreeze when I worked on the Railroad and I still have some, it's purple in color and I still have some of the additive. Thanks again
Little Bill
You just need to find another dealer. My dealer in Tacoma WA has both. I agree that you can never get all the flush water out and by putting 50/50 in you are automatically diluted below the optimal mix. I like to use the fluid designed by and recommended for my Cat engine and if I pay $50 more every 7 years (or whatever you particular change schedule is) my peace of mind is worth the small difference in price. My rig holds 54 quarts on initial fill so I buy a couple more gallons than you do, but its still worth it to me to use the Cat coolant.

You may want to check the price between 50/50 and concentrate and see if it's cheaper to buy all concentrate and top off with distilled water from Wally World/KMart/Safeway. When I changed some last year it was more economical to use all concentrate.

Bill, that sounds like a good plan to me. You always have a bit of flush water left in, use the concentrate as discussed and check your mix with an antifreeze tester as you top it off. Just don?t forget to bleed the system of air when you are finished. If you want to stick with Cat that is fine. OEM is always a good choice in any case, I just wanted to point out the savings and as you know the RR wouldn?t use it if it was inferior.
Either way I would also recommend getting the extender now and throw it in the bin so you have it. I usually mark the date the ELC was installed on duct tape back by the fill neck and then the date the extender needs to be added, otherwise most people don?t remember when it needs to be added. This way you see it when checking fluid levels, etc.
I carry 1 gal of concentrate (some prefer premix here) and 1 gal of distilled water in my bay (along with other fluids-filters). I use the water in the batteries also. Hate to keep adding to your work load but I would also do the genset at the same time with the same stuff. You should be back on the road in no time!  :)
Ken, you must be talking about MP&E. A bit spendy but good guys there.
NC Machinery is the local dealer for me. There are other Cat authorized repair shops but NC seems to give me the best pricing.

I think most diesel/electric loco's are GM diesels so it seems logical they would stay with that brand coolant. Like Mavarick says, OEM is always a safe bet.

Cat ELC users can also use the test strips and determine when to put the extender in. A lot of anectdotal evidence points to motorhomes not necessarily needing the extender as often as a higher mileage unit would (the 3 year recommendation in the book). I had my motorhome tested last spring during it's oil change and after 5 years it's still in the good range and extender is not recommended. My boat tested out of range last year after 5 years that I'd owned it. It might have been ok to use extender in it, but I had no records to show if extender had already been used, so out of caution it got changed.

Ken, you must be talking about MP&E. A bit spendy but good guys there.
Ken, reason I said MP&E is because you said Tacoma. It is much closer than Tukwila and both dealers and owned by same group. They call it a rental store but has parts/service also.
I think most diesel/electric loco's are GM diesels so it seems logical they would stay with that brand coolant.
That?s correct but the EMD and DD engine division are separate. If I had to guess I would say they use the same formula as most large companies, purchasing contracts, and DD won the bid. I used to hate the practice but they seem to be the way now.
Like Mavarick says, OEM is always a safe bet.
Just so I don?t get flamed from the aftermarket folks I am a proponent of saving money IF you do your homework first. If you don?t know what to use then the OEM is always safest. However, more $ is not always a better product. If that was the case, when you brought your MH in to a Freightliner dealer for service they would use Cat oil, filters and ELC and not Alliance brand.
If you prefer to do an ELC field test or an SOS, fine. It probably would get you another year or so in a MH. Cat says 6000 hrs OR 3 yrs, whichever comes first. My point with the extender is to do something, just don?t forget or it will cost you.
I think the riskiest thing I see people taking for granted is filters. I see a lot of crosses that are just plain wrong and done for the wrong reason so what are you saving, $2 - $3 dollars maybe. If you don?t understand Beta ratios and filter construction then play it safe here for sure. A $9 Cat oil filter will work as designed. I pick up 4 or 5 every time I go to the dealer. JMO, do whatever helps you to sleep (or spend more time Rv'ing)!  :)
I use the NC Machinery Cat dealership on Pacific Highway, one city block outside the Tacoma City limits, technically in Fife, but on what is commonly called the Tacoma tide flats. Tukwila would be much further away from my Puyallup home.

I'm not familiar with what brand filter Freighliner Dealers use since I never take my Roadmaster chassis MH to them for service, but every place I've been for an oil change has always had either exclusively Cat filters or Cat filters and their house brand, They always asked which I wanted.

Thanks to all who have responded. I finally located the Cat concentrated antifreeze at Carter Cat Ashland Va. They are the earth moving/heavy equipment dealer here.  The other Carter Cat works on trucks and generators mostly. Although they have the same name they are not associated. Long story. Anyway we flushed the system about five or six times and did the distilled water on the last flush. One guy on another forum said his C9 held 13 gallons so I went with that amount (ours is a C7). I called Freightliner and Winnebago and neither could give me an answer on the capacity of the cooling system. Winnebago rep. walked out into the shop and ask a worker who guesstimated 2 gallons was left in the system after draining the radiator. Here is how we calculated. If we drain 8 gallons out, that leaves approximately 5 gallons in the system so I added 5 1/2 gallons concetrate and topped it off with 2 gallons of 50/50 mix. This is for 13 gallon capacity system. It may be a little rich but I can always dilute it down. I plan on driving it today and get it up to temp so everything will mix good. I'll check the freeze protection and SCA content when it cools down. Boy these things are high maintenance. Anyway it's just what a retired couple needs.
Little Bill

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