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Topic: Coolant flush C8.3 (Read 731 times) previous topic - next topic

Coolant flush C8.3

Getting ready to replace thermostat and coolant on 1997 C8.3 325 hp. I have several questions after reading my engine manual and many posts including the Beam Alarm info and the Wolfe report. I've also read a good article in Motorhome Magazine about changing over to OAT.

Thermostat: Gave the parts guy at Cummins my serial number and he provided me with a thermostat. One thermostat, not the two that show up in my manual. However, this looks correct judging from the housing. No gasket was provided. Thermostat is 3913028. Does it need a gasket?

Coolant: I'm switching from standard green to Fleetguard ES Compleat OAT. They use NOAT 1:1 at the dealership, but I special ordered OAT undiluted. Will flush once with city water, and then flush twice with distilled as per Brett. Fill with undiluted to 50 percent capacity and then top off with distilled water.

Procedure for flushing: According to Chuck & Jeannie post in a thread two years ago, on his C8.3 when they changed over to ELC they pulled off the coolant filer, left shut off valve open to drain, then closed shut off valve and flushed three times, then replaced with blank filter when filling for last time with concentrate and opened shut off valve at the filter housing. If you don't shut off old coolant filter, will it keep feeding in SCAs while you flush?

Thermostat replacement: At what point should I replace thermostat? If it turns out I need a gasket, I will be stuck in the final drain sequence and the engine and radiator will probably be filled with water only for about four to seven days. Will that be a problem?

Purging air: I can't find the purge valve shown in my Cummins Engine manual, perhaps because mine has the single thermostat vs. double. There are two lines from upper radiator pipe and water filter housing that run directly to the surge tank. They come into the tank below the pressure cap. I'm thinking that if I run the engine with the heater on hot, fan low, and cap off, it will purge itself of any trapped air through those two lines and into surge tank. I just need to keep the tank full while running with cap off.

Hoses: I have not changed out my hoses. Currently no leaks and appear in good shape and Cummins shop did not report bad hoses two years ago when it flushed the coolant system. Coach has 67,000 miles. Should I go ahead and order all new hoses? I'm thinking some of them will be non-standard and may need to come from FOT.

Just changed oil and fuel filters. That's another post. Headed out in August for a six to seven -thousand-mile swing west to Colorado, Portland, Gig Harbor, San Francisco, and back to North Texas.  Start work on it July 1.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.

Re: Coolant flush C8.3

Reply #1 –
Quote from: Realmccoy –
Procedure for flushing: According to Chuck & Jeannie post in a thread two years ago...
I had to go back and re-read my post about our radiator service at Oregon Motorcoach (Newbie Coolant Change Question).  It's not that I'm getting forgetful, you understand...

The reason they removed the old coolant filter was so they could open the filter valve to allow air to flow into the block when draining the coolant out the bottom drain valve.  Also removed the cap on the metal coolant tank.  Did that for each drain.  Speeds up the drain process.

They told me the engine would purge itself of air as we drove for the next few days.  You just check the plastic overflow bottle every morning, and keep adding coolant to bring it up to the "cold" level mark.  I only had to add some for a couple mornings - after that the "cold" level in the overflow bottle stabilized.

I didn't have them change the thermostat (or stats - I don't know if our engine has one or two) so can't answer about gasket.

I also did not change any hoses.  The mechanic said our hoses looked fine.  As far as I know they are still original factory installed, and we are now approaching 200k miles with no leaks.  I will probably install new hoses and thermostat(s) next time I do the coolant service.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Coolant flush C8.3

Reply #2 –
Thanks for the clarification. That really helps.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.

Re: Coolant flush C8.3

Reply #3 –
Change the hoses now or later,I would do it now,there is a small part numbered hose near the thermostat housing also,will look in my parts book and try and find the gasket number,there is a gasket.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Coolant flush C8.3

Reply #4 –
I would also change radiator cap and small return hose to metal tank from plastic tank.  Mine leaked allowing air to enter radiator
97 U295 40, Build #5040, 6C8.3 325 HP
Oregon Continuous Traveler
Samsung Residential #RF20HFENBSR,
Xantrex SW2012, (3)AGM8D Hse, (2)AGM Grp24 Eng, Victron BMV-712, 1800w Solar 4 LG & 2 Sunpower
Extreme Full Body Pt w/hdlmps, new furn/floor, 4 down Lexus 2004 GX470 AWD curb weight 4,740 lbs
Prev: 1990 Barth, 10L 300 2 yrs; 91&92 Monaco Signature, 10 yrs, 10L C 300 &  6C8.3 300; 1997 ForeT 6C8.3 325 since May 2017.  Employed by Guaranty RV 14+ yrs.  Former VW New Car Dlr/Service Dlr, Sales Mgr, Rv Sales, and Service Adviser from 1968-2017
"Don't criticize what you can't understand" Bob Dylan
 

Re: Coolant flush C8.3

Reply #5 –
You have high quality hoses.  If they've recently been inspected by a professional, replacing is unnecessary.  My thermostat after 207,000 miles is still original.  Since I can watch engine coolant temp so easily, I will know if it malfunctions.
Regards,
Brett

'99 42' Foretravel Xtreme
'14 Brown Motorsports Stacker
'05 Chevy SSR
'02 BMW R1150R