CAT C7 Fluctuating Temperature

[Dick1142]

ps....while you are in there, you might want to check the serpentine belt. Mine had started to fray on the edges. Very easy to change...a 10 minute job. I was surprised, and it was only $45 at NAPA.

[Dick1142]

Originally Posted by Dick1142

Just changed mine, and actually it was very easy. Good access thru the closet floor.

"Mine" = thermostats.

[Keith K]

I'm the OP and finally got around to changing the thermostats...err "regulators". Two of them and the gasket were $51 at a CAT dealer. Not technically difficult, but would have been easier if I didn't have to fight a rusted hose clamp. One of the thermostats was broken & the bottom half was lodged in the housing. Pried it out, replaced them, and after 1000 miles the temperature holds rock steady at 188. Thanks for all of the advice.

[Jorr2600]

I had the same issue with temp gauge. Found both thermostats bad and one had broken with the bypass valve floating around in the coolant. Replaced both and cured the problem.

[FIRE UP]

Originally Posted by Keith K

I'm the OP and finally got around to changing the thermostats...err "regulators". Two of them and the gasket were $51 at a CAT dealer. Not technically difficult, but would have been easier if I didn't have to fight a rusted hose clamp. One of the thermostats was broken & the bottom half was lodged in the housing. Pried it out, replaced them, and after 1000 miles the temperature holds rock steady at 188. Thanks for all of the advice.

Hey Keith K,
Just got around to reading this thread again and see that you have in fact, changed them and it did make the difference you were looking for. This is great news. Our coach, an '04 Itasca Horizon 36GD with the C-7 330HP CAT, is now close to 11 years old and, still has the original ant-freeze, hoses, thermostats (regulators) etc. The radiator has been changed, by me, and the belts. I figure it's just a matter of time before I have to get in there and lay on this fat gut of mine, on top of that engine, and change those t-stats. Good news.
Scott

[1ciderdog]

Originally Posted by FIRE UP

Hey Keith K,
Just got around to reading this thread again and see that you have in fact, changed them and it did make the difference you were looking for. This is great news. Our coach, an '04 Itasca Horizon 36GD with the C-7 330HP CAT, is now close to 11 years old and, still has the original ant-freeze, hoses, thermostats (regulators) etc. The radiator has been changed, by me, and the belts. I figure it's just a matter of time before I have to get in there and lay on this fat gut of mine, on top of that engine, and change those t-stats. Good news.
Scott

Fire up - changing those thermostats (regulators) will not be much of a challenge for you. Not much to it, remove a couple or more bolts, remove the housing & regulators, clean the surfaces and install. Did mine a couple of years ago and don't remember any problem or surprise except the temp gauge started showing 188 instead of 190 on flat surfaces/normal driving.

[mchero]

Just put 6.5K on our Discovery the first 2 months of full timing. She runs at 192 & on hard/hot pulls never got past 200 but I think I should pull the rads & clean. After reading this post will also swap out the stats as well. Great thread! Thanks!

[docj]

Originally Posted by FIRE UP

Our coach, an '04 Itasca Horizon 36GD with the C-7 330HP CAT, is now close to 11 years old and, still has the original ant-freeze, hoses, thermostats (regulators) etc.

Was your MH delivered with glycol-based green antifreeze or with extended life coolant (ELC)? If it was glycol that does seem like a rather long time to have the same coolant in it. I assume you monitor the SCA's? Even ELC should be changed occasionally.

[FIRE UP]

Originally Posted by 1ciderdog

Fire up - changing those thermostats (regulators) will not be much of a challenge for you. Not much to it, remove a couple or more bolts, remove the housing & regulators, clean the surfaces and install. Did mine a couple of years ago and don't remember any problem or surprise except the temp gauge started showing 188 instead of 190 on flat surfaces/normal driving.

1ciderdog,
I surely thank you for your encouragement pertaining to my abilities. As time goes on, my "abilities" seem to be thinning out some. But, I suppose that regulator change out operation will still be in the realm of me being able to turn a few wrenches. This winter I'll dive into it.
Scott

Originally Posted by docj

Was your MH delivered with glycol-based green antifreeze or with extended life coolant (ELC)? If it was glycol that does seem like a rather long time to have the same coolant in it. I assume you monitor the SCA's? Even ELC should be changed occasionally.

Hey docj,
The anti-freeze that's always been in the coach since we purchased it, just over 4 years ago, is the pink stuff. I have one of those anti-freeze testers (little cheapie thing) and, it keeps telling me everything is just fine. I know, I know, I should purchase some test strips and test it. I had some in my hand at the Freightliner service center but, as I understand it, those have a shelf life. So, I'll have to get some new ones.

I'll also, fairly soon, have to take an inventory on all of the hoses etc. that should be replaced before they fail me while out on a trip. That would suck big time.
Scott

[docj]

Originally Posted by FIRE UP

Hey docj,
The anti-freeze that's always been in the coach since we purchased it, just over 4 years ago, is the pink stuff. I have one of those anti-freeze testers (little cheapie thing) and, it keeps telling me everything is just fine. I know, I know, I should purchase some test strips and test it. I had some in my hand at the Freightliner service center but, as I understand it, those have a shelf life. So, I'll have to get some new ones.

I'll also, fairly soon, have to take an inventory on all of the hoses etc. that should be replaced before they fail me while out on a trip. That would suck big time.
Scott

Those test strips are for testing SCAs in glycol antifreeze. They won't do anything for the red stuff which is ELC. You need a lab analysis if you want to know the condition of that coolant.

[Steve Ownby]

Originally Posted by docj

Was your MH delivered with glycol-based green antifreeze or with extended life coolant (ELC)? If it was glycol that does seem like a rather long time to have the same coolant in it. I assume you monitor the SCA's? Even ELC should be changed occasionally.

The C7 is a parent bore engine and is not susceptible to cavitation damage. No SCAs required. That coolant is pretty long in the tooth. I would plan on a flush/fill. I would go with Cat's recommendation.


Steve Ownby
Full time since '07

[jdealcpa]

I had exactly same problem on my 2006 C-7 85000mi.. Replaced both thermostats and for good luck radiator cap. Problem solved. Simple job!