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Old 12-27-2017, 07:01 AM   #1
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Cooling System overhaul on my Cummins ISC-315 engine

My 2000 Monaco Diplomat came with a Cummins ISC-315 engine.

I've owned it about 3 years, and since I've owned it, I have had to replace coolant after every significant trip (200 miles plus). At least 1/2 to 1 gallon.

It also ran very warm to hot crossing the high mountain passes I encounter traveling in the SW an Western parts of the US.

I checked all the radiator hoses and heater hoses, including the small return lines to and from the coolant reserve tank, and found them to be less than satisfactory. I discovered a few slow leaks and decided it was time to fix the issue before it became a deadly problem.

I purchase new high temperature/high pressure 2.25" radiator hoses for the lines to and from the radiator. Also, I bought a new radiator hose for the reserve coolant tank to the radiator, and a 25' of 5/16" hose for the return lines from the radiator and engine head. In addition, I bought some 5/8" hose to make shunts for my heater hose connections. The core on my front heater apparently had leaked in the past, and was bypassed anyway. Bought a new thermostat with new O-ring gaskets too. I had replaced the radiator cap about two years ago thinking that could be an issue.

Drained and collected all the coolant from the system. Flushed the motor (with the thermostat removed), and the radiator with a garden hose. I then removed the complete input an output lines from the motor/radiator. I disassembled them, cleaned them, and replaced with the new hoses. I then Installed both 2.25" lines with the new thermostat. I removed the plastic tank to check for cracks or other damage. Mine was good (a NOS one was $300.00). It looked like a replacement, based on the stories I had read of these failing. Connected the 1.25" line from the side of the radiator to the bottom of the reserve tank, and replaced the two 5/16" lines from the radiator and engine head. Also made 5/8" shunts for the heater feed and return lines.

I had contacted Cummins and asked what coolant they suggested as a replacement. They replied - Fleetguard Compleat ES OAT. Found a brand new Cummins Dealership very near me in Fresno, and purchased 9 of their 11 gallon inventory. Should have bought all 11. I'll explain later. Refilled the system from the reserve tank. Apparently the 5/16" return lines help bleed air from the system on a refill, because it took 8.5 gallons initially to get to the "max" mark on the reserve tank.

So far so good. Drove it 460 miles from Fresno CA to St. George UT recently, and noticed only a small drop in the reserve tank, about 1/2 gallon. I attribute that to air in the system. Also, one of those pesky brass fittings on the top of the reserve tank leaked a small amount of coolant, as they seem to always have done in the past. Hard to get a good seal with those. Made another attempt to reseal it just a week or so ago.

I have also cleaned the exterior fins of the radiator a few times over the last year. Between that and the new coolant, it appears to run much cooler, although it could also be the time of year. I'll know better come summer time.

Next trip 1/1/18 to Camp Verde AZ.

My biggest complaint/concern with this whole project, The coolant Cummins suggested is very hard to come by. Not one local distributor (in St. George or Hurricane UT) stocked it or could get me more of it (as a safety buffer) in the time frame before leaving St. George UT. That's really annoying.

I did a lot of research online, and found a red organic coolant manufactured by Peak, called Final Charge Global Extended Life. It was the closest match to the Fleetguard product and claims to be compatible with other red coolants. I found it a local O'Reilly's and purchased two gallons as my reserve. It's recommended for Cummins engines as well.

Things I learned:
1) Having a help-partner would have really made easier the removing and replacing the 2.25" lines from the engine-radiator. Especially the replacing part.
2) I wish now I would have used the Peak Final Charge coolant as the replacement. Finding it in even a small town like Hurricane UT is not an issue, and it seems as good a replacement as the Fleetguard product.

Kind comments and questions accepted. Negative comments not needed.
I have a family for those.
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Old 12-27-2017, 07:29 AM   #2
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Old radiator hose images

RADIATOR HOSE COMING OUT OF BLOCK - 90 DEGREES, 2.25 INCHES ID.jpg (252.5 KB)

This photo is turned sideways. Won't post vertical.
RADIATOR - INLET TO RADIATOR, ABOUT 12 INCHES LONG, 2.25 INCHES ID.jpg (173.0 KB)
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ID:	186928   Click image for larger version

Name:	RADIATOR - INLET TO RADIATOR, ABOUT 12 INCHES LONG, 2.25 INCHES ID.jpg
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Old 12-27-2017, 07:38 AM   #3
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Sounds like you covered all the bases. Hopefully now you won't have any more cooling issues.

Last summer I changed out my coolant in my ISB 325hp Cummins in my 07 Neptune. I replaced the nylon/plastic surge tank with the one from Source Engineering cause I didn't trust that one 10 years old now. I used the Final Charge coolant cause of it being so readily available.

I did not replace my hoses at the time because mine still really looked like new even though they were 10 years old. Maybe I should have, I don't know. Did you have any trouble finding the 2.25" hoses? Where did you get them? I've read on here some people ended up just trying to match them up at a parts store.

Congrats on the job well done.

Chad
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Old 12-28-2017, 07:30 AM   #4
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Hey Chad,

I found the new 2.25" hoses in many places online. I tried going to some local auto parts stores, but they only wanted to provide the OEM-like rubber replacements, and I'd have to bring the old ones in to match.

I found the ones I purchased on Ebay, and for less than the price of the rubber ones at the auto parts store, I got the blue high pressure, 4 ply silicone hoses. I ended up buying 2 - 90's, and 1 meter length of straight hose for the radiator to engine lines. The input and output lines are a combination of hoses and steel pipe for the runs. I took them completely out, disassembled them, cleaned them and reassembled them before reinstalling. I did use the old hose clamps as they were very well made and in great shape.

The truth is though, that I believe the 5/16" return lines from the engine head and radiator to the surge tank were the biggest culprits. They were dried and cracked, and the connection at the engine head didn't even have a clamp on it. Duhuh!! Also, the large hose (1.25") from the bottom of the surge tank to the side of the radiator was in pretty bad shape. $15.00 at O'Reilly's - matched by the number on the old one, and shortened a bit. Don't forget those long 5/8" heater hose runs too. You lose those, you might as well lose one of the main 2.25" feeds. Like I said, I made short shunts for those because my heater core apparently leaked in the past. That's a bear to replace.

I do like the aluminum replacement tanks (about $400??), but my plastic/nylon tank was in good shape. Maybe in the future.

Overall, I really took my time with this project, and spent about 12-16 hours on it, over 3 days. I'm glad I did it, because now I know all the rubber is replaced, the clamps tight, the motor and radiator were flushed, and the coolant replaced with a good product. Can't say I have lots of faith in many diesel repair and RV repair shops. I've met some really good mechanics at them, and some real con guys. Problem is, you never know which one you're talking to till the end of the repair sometimes.
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Old 12-28-2017, 08:12 AM   #5
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Quote:
Originally Posted by thesoundguy View Post
Hey Chad,

I found the new 2.25" hoses in many places online. I tried going to some local auto parts stores, but they only wanted to provide the OEM-like rubber replacements, and I'd have to bring the old ones in to match.

I found the ones I purchased on Ebay, and for less than the price of the rubber ones at the auto parts store, I got the blue high pressure, 4 ply silicone hoses. I ended up buying 2 - 90's, and 1 meter length of straight hose for the radiator to engine lines. The input and output lines are a combination of hoses and steel pipe for the runs. I took them completely out, disassembled them, cleaned them and reassembled them before reinstalling. I did use the old hose clamps as they were very well made and in great shape.

The truth is though, that I believe the 5/16" return lines from the engine head and radiator to the surge tank were the biggest culprits. They were dried and cracked, and the connection at the engine head didn't even have a clamp on it. Duhuh!! Also, the large hose (1.25") from the bottom of the surge tank to the side of the radiator was in pretty bad shape. $15.00 at O'Reilly's - matched by the number on the old one, and shortened a bit. Don't forget those long 5/8" heater hose runs too. You lose those, you might as well lose one of the main 2.25" feeds. Like I said, I made short shunts for those because my heater core apparently leaked in the past. That's a bear to replace.

I do like the aluminum replacement tanks (about $400??), but my plastic/nylon tank was in good shape. Maybe in the future.

Overall, I really took my time with this project, and spent about 12-16 hours on it, over 3 days. I'm glad I did it, because now I know all the rubber is replaced, the clamps tight, the motor and radiator were flushed, and the coolant replaced with a good product. Can't say I have lots of faith in many diesel repair and RV repair shops. I've met some really good mechanics at them, and some real con guys. Problem is, you never know which one you're talking to till the end of the repair sometimes.
Thanks for replying thesoundguy. I agree with you about repair shops. You read so many horror stories it's hard to trust just anyone. That's why I do as many of the repairs as I feel comfortable.

When I changed my surge tank out last summer I replaced all of the smaller hoses. Jim at Source Engineering said he had heard of some of those failing, so I went ahead and replaced all of them, Including the medium size hose from the bottom of the tank to the block. The hoses that lead to the heater core up front are original and appear to be in good shape like the bigger hoses around the radiator. I do dread changing them a few years down the road. Hopefully i won't have to sooner, or worse yet on the side of the road.

Again, thanks for the info. That gives me something to go on looking forward to when I have to change mine.

Chad
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