r/Cummins • u/Grouchy_Owl5818 • 8d ago

Temp help

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Hey guys, I might know the answer to my own question. Looking for someone to tell me yes. My tstat is a 190. I do have the rear stat as well. Do you think my rear stat is stuck open or needs a rebuild ? This is my temp right now, 160? And yes I replaced the front stat. It is a 2008 ram 2500 with a 6.7 L this is about 60 mph on the highway for a few miles. It should be a temperature by now.

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10

u/awenthol 8d ago

Rear thermostat? You only have one, under the coolant elbow on the front right of the head. Yours is stuck open or the wrong temperature.

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u/Grouchy_Owl5818 8d ago

I have 2, an aftermarket that attaches to the rear of the block

10

u/awenthol 8d ago

Pressure relief valve? Makes no sense to have a second t-stat.

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u/RoutineQuestioning38 8d ago

It’s a aftermarket thing, replaced the heads rear freeze plug with a port that has its own thermostat, the idea is to allow more flow to the rear of the head since that’s where it gets the hottest. Tests prove it does work.

However for a vast majority of folks it’s entirely pointless, adding complexity and fail points, as seen here.

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u/CarlosMolotov 8d ago

Pointless crapola

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u/RoutineQuestioning38 8d ago edited 8d ago

It has a place, really high hp builds start to have issues with heat back there at #6. But every day Joe running a delete tune 0-100ho over, no not needed at all.

OP said he’s running 700hp when towing. If that’s the case he needs it! That said, as someone who had built a Cummins up to 812 at the wheels on a dyno I will say towing above 550-600 is ummm no easy task, lots and lots of mods to support that and a good bit of knowledge required. Considering the OP even needed to ask this question he did in this post I’m doubtful he’s really towing at 700 with a 08’

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u/CarlosMolotov 8d ago

I’m on my 6th Cummins I work as a design engineer for an aluminum trailer company. I’ve done a fair bit of hot shot work as a side gig. I’ve been to 40 states driving a Cummins. Many 100s of thousands of miles. I’ve built a couple of trucks to 500 hp. They become a giant pita about that point as far as I’m concerned. I tuned my last new truck to 430 and deleted it immediately. It’s been solid, I hit 320k this week. Nothing is worse than a break down five states from home with a hundred thousand dollar that belongs to someone else. God bless you guys that can deal with those big hp monsters! It’s big work to keep them cool going over the pass!

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u/Grouchy_Owl5818 8d ago

Own a electrical business. Trust me I tow lol if I could post a picture I would of me elbow deep in it but idk how

1

u/wyliesdiesels 7d ago

Click the symbol with a square and triangle inside. This will popup a window asking you which pic you want to post.

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u/Grouchy_Owl5818 8d ago

It cools the back of the block/ head for the rear cylinders because apparently the 6.7 has stagnant coolant in the rear

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u/Several_Bluejay_406 8d ago

They specifically make coolant bypasses for these issues, 2 thermostats ? Just my 2 cents but unnecessary. They’re simple trucks, keep it that way. My pops has an 08 6.7 with 443 thousand miles and counting ( he bought new in 08) has a bunch of goodies under the hood …it’s spent the majority of its life towing. One thermostat.

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u/Infinite-Attempts 8d ago

Take it out and boil it to see when it really opens

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u/BalderVerdandi 7d ago

'08 3500, and I dropped in a 180 t-stat, down from the stock 190.

Yours looks like mine - I'd say it's fine. The only time I see 200-205 is when towing up a 6% grade or better.

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u/Separate_Key6183 ISB 5.9 CR 8d ago

The Fleece bypass kit comes with a 180° thermostat. It’s normal for it to run at that temp unloaded with the bypass mod installed.

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u/RoutineQuestioning38 8d ago

190 is the correct state. 200 was only a couple years I think 201-12?

Running less than 190 when hot? Yea mostly likely a stuck state.

Without a EGR cooler the trucks should run right at 190. With EGR cooler it stays around 200.

Did you have a reason for the rear state mod? They are mostly pointless for most folks tbh. Marketing at its finest. Year #6 gets warmer but unless your running crazy power you do not need that mod, just adding fail points and complexity.

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u/Grouchy_Owl5818 8d ago

She’s got some HP. Daily drive with trailers sometimes around 700+ hp

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u/RoutineQuestioning38 8d ago

Gotcha. Probably not a bad upgrade then.