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Cat C9 Thermostat Replacement

Yahoo Message Number: 86815
I want to replace the thermostats in my Cat C9 engine but do not intend to do a complete drain and flush of the coolant since it has the Cummins PPG ELC coolant. I found some Cat instructions for replacing the thermostats on a Cat C15 that, in essence, said to drain enough coolant to drop the coolant level below the thermostat level, remove the housing and replace the thermostat elements, replace the housing, and add coolant to bring the level back to normal. This is basically the same process I have always used to change thermostats in my cars. However, I have read various posts that indicate that after replacing the thermostats in a C9 and refilling with coolant, a special procedure must be completed to remove air from the system. However, I have not been able to find out what this procedure is. For those of you that might have replaced the thermostats in your C9 engine, have you performed an air-bleed process of any kind? If so, could you share it with me? Also, did you require any special tools to remove/replace the upper thermostat housing and/or the thermostats themselves? Any other special tricks or things I should watch for in changing out the thermostats?

John

'06 Inspire Da Vinci #51905

Re: Cat C9 Thermostat Replacement

Reply #1 –
Yahoo Message Number: 86816
John, I replaced the two thermostats in my C9 last year. You will need to drain enough coolant to get it below the thermostats. That won't require a lot to be drained as the thermostats are at the top of the engine. The most time consuming part is removing the old gasket off of the engine. mine was quite stuck and it came off in small pieces. Make sure you plug up the coolant passage so you don't get any gasket material into the cooling system. I didn't do anything special to bleed air from the system. The top of the thermostat housing has an allen head screw you can loosen up until you see coolant leaking around the threads.
You should have bleeder hoses going into the top of your expansion tank. If you trace them to their source you will see they bleed the upper parts of the cooling system. I've driven my coach over 12,000 miles since I changed the thermostats. All is well Good luck,
RJ

2005 Inspire
#51264

Re: Cat C9 Thermostat Replacement

Reply #2 –
Yahoo Message Number: 86824
Thank you so much for the reply - that is exactly the information I was looking for - guess my afternoon activity is now set - change them out!

Regards,

John

'06 Inspire Da Vinci #51905

Re: Cat C9 Thermostat Replacement

Reply #3 –
Yahoo Message Number: 86861
Friend make sure you test strip you Coolant. In my other life saw many an engine failure due to old acid bearing coolant. Ken Retired Cat Tech. 99 Allure 30356.

Re: Cat C9 Thermostat Replacement

Reply #4 –
Yahoo Message Number: 86863
Thanks Ken, but I am running the OAT technology, Peak Final Charge, in my coach.
RJ

05 inspire #51264

Re: Cat C9 Thermostat Replacement

Reply #5 –
Yahoo Message Number: 86881
To those who have replaced the two thermostats (regulators)
The parts book shows a small 'valve' sited between the two 'stats - have you / did you replace this at the same time?

Thanks

Ian S

Allure 430 - #31321
Cat C9 400hp

Re: Cat C9 Thermostat Replacement

Reply #6 –
Yahoo Message Number: 86886
I did not replace the valve between the two stats.
RJ

2005 Inspire #51264