Truck refuses to come up to temp?

U

USMCShooter

BrokeandSmiling
Joined
Jul 24, 2020
Messages
27
New engine has 2500-ish miles on it...been running and performing absolutely perfect...shut it off at a store, fired it back up and did a gauge scan...temp gauge wasn’t registering and CTS said 138 degrees....drove a few miles home, didn’t climb. Changed temp sensor and thermostat...nope...put a new radiator cap today...it would only get to 150...I’m baffled as hell...wiring looks good, not popping any codes...hoses are soft...no leaks...I’m out of Schlitz...anyone experienced this?
I don’t know if I’ve got a gauge/computer/indication problem? Both rad hoses and heater hoses are not to hot to hold...just haven’t got a clue.
 
I’ve heard water gurgling behind the dash, but attributed it to the Fleece bypass...so that 1-inch hose will keep the engine from coming up to temp!? I put a new main thermostat in it...the bypass still depends on the main thermostat opening to bypass doesn’t it?
 
The bypass relieves pressure when the thermostat cant keep up, it bypasses the stat. Maybe try clamping your bypass line and see if it will warm up? The smallest chunk of anything in the coolant system will make my 12 valve stat stick.
 
I can tell you from experience that then a bypass sticks open it will not let your truck get up to temp. I can run around all year and never see more than 175* in the heat of the summer. In the winter the truck will not even make heat unless I have the cold weather front on and the bypass hose restricted. I highly recommend installing a ball valve in line and closing it just to see if that is the issue.
 
Take the fitting out of the by pass return block at the thermastat housing and tap the inside of the fitting to 1/4npt and put a plug in it. 5 minutes will prove if it’s the coolant by pass or not then you can go to taking it off and messing with it
 
I replaced my thermostat with a O'Reillys aftermarket
brand. Truck would run about 140 top, and cause it to go in limp mode.

replaced it again with a OEM Thermastat, and problem went away.
 
jasonc said:
I replaced my thermostat with a O'Reillys aftermarket
brand. Truck would run about 140 top, and cause it to go in limp mode.

replaced it again with a OEM Thermastat, and problem went away.
Click to expand...

I had same problem on an old 12v daily driver I had. Auto parts stores sell thermostats by operating temp and size. Got OEM thermostat and problem gone. The oem thermostat has smaller openings and a thick rubber center section.
 
I clamped the line down and sure enough, truck came right up to temp, main Stat is working perfectly...now I'm highly pissed at Fleece! I called a couple of buddy's of mine that have been modding these trucks for years, both have at least three of them....BOTH have had issues with the Fleece bypass Stats breaking at anything over 3200 RPM's. BOTH have talked to Fleece about it in the past....turns out it's a fairly common problem on trucks that see over 3000RPM, even irregularly.
No where on Fleece's description or site does it say anything about not handling additional RPM's....Turns out they put a Stat from a SBC in the damned things....so, I'm guessing I've FUBARed the SBC Stat in it and it's stuck open....I've got to completely disassemble the truck with the Pusher Twins on it...piping, exhaust, inner fenders, etc. This bypass has been nothing but a PITA since I put it on with the build...leaked after engine install....had it out 3 times trying to stop it....finally RVT'd the damned thing and it quit....now the Stat is stuck open within 2500 miles....I'm not pulling the damned thing back off....I'm going to put a Watts valve in the Fleece line and set it for 35psi...I'll never spend another dollar with Fleece....they're well aware this is an issue....
 
USMCShooter said:
I clamped the line down and sure enough, truck came right up to temp, main Stat is working perfectly...now I'm highly pissed at Fleece! I called a couple of buddy's of mine that have been modding these trucks for years, both have at least three of them....BOTH have had issues with the Fleece bypass Stats breaking at anything over 3200 RPM's. BOTH have talked to Fleece about it in the past....turns out it's a fairly common problem on trucks that see over 3000RPM, even irregularly.
No where on Fleece's description or site does it say anything about not handling additional RPM's....Turns out they put a Stat from a SBC in the damned things....so, I'm guessing I've FUBARed the SBC Stat in it and it's stuck open....I've got to completely disassemble the truck with the Pusher Twins on it...piping, exhaust, inner fenders, etc. This bypass has been nothing but a PITA since I put it on with the build...leaked after engine install....had it out 3 times trying to stop it....finally RVT'd the damned thing and it quit....now the Stat is stuck open within 2500 miles....I'm not pulling the damned thing back off....I'm going to put a Watts valve in the Fleece line and set it for 35psi...I'll never spend another dollar with Fleece....they're well aware this is an issue....
Click to expand...

I understand you're pissed but welcome to the world of aftermarket mods. If you wanted zero issues and minimal maintenance, should have left it stock. I would just delete that bypass altogether and run billet freeze plugs and if need be trim the water pump a bit.
 
That watts valve will corrode and leak externally and stick open just the same, mine is stuck and leaking right now as a matter of fact. Vince gave good advise. Good luck
 
Vincejax said:
I understand you're pissed but welcome to the world of aftermarket mods. If you wanted zero issues and minimal maintenance, should have left it stock. I would just delete that bypass altogether and run billet freeze plugs and if need be trim the water pump a bit.
Click to expand...

Vincejax, while your "should have left it stock" is unwarranted, since the bypass is actually recommended by Fleece as one of the 1st mods that should be done to a stock engine for longevity when towing heavily, I didn't expect zero issues, no one who has spent any time around true performance vehicles would ever expect zero issues...that being said, there are thousands of modified trucks running around at my power level virtually trouble free....

My disgruntlement is more to do with zero cautions or warnings in Fleece's lengthy description of the part and why you NEED it on your truck if you modify it or tow heavily....cautioning potential buyers regarding modified RPM ranges creating vastly increased pressures and potentially damaging their product would certainly be nice to know when planning an engine build and including their product in the plan...when they KNOW this is an issue...one would think a disclaimer (For vehicles accelerating beyond cummin's factory established maximum RPM range, damage to thermostat may be experienced) or something along those lines....
 
95cummins5.9 said:
That watts valve will corrode and leak externally and stick open just the same, mine is stuck and leaking right now as a matter of fact. Vince gave good advise. Good luck
Click to expand...

At least you can reach the Watts valve without disassembling the entire truck to correct the issue....
 
USMCShooter said:
Vincejax, while your "should have left it stock" is unwarranted, since the bypass is actually recommended by Fleece as one of the 1st mods that should be done to a stock engine for longevity when towing heavily, I didn't expect zero issues, no one who has spent any time around true performance vehicles would ever expect zero issues...that being said, there are thousands of modified trucks running around at my power level virtually trouble free....

My disgruntlement is more to do with zero cautions or warnings in Fleece's lengthy description of the part and why you NEED it on your truck if you modify it or tow heavily....cautioning potential buyers regarding modified RPM ranges creating vastly increased pressures and potentially damaging their product would certainly be nice to know when planning an engine build and including their product in the plan...when they KNOW this is an issue...one would think a disclaimer (For vehicles accelerating beyond cummin's factory established maximum RPM range, damage to thermostat may be experienced) or something along those lines....
Click to expand...

This is nothing more than hotrodder's expectation vs reality.
 
Vincejax said:
This is nothing more than hotrodder's expectation vs reality.
Click to expand...
While I agree with your sentiment, I'd be interested to know how many people have been down over the piss poor quality hose they packaged in those kits. I had to R&I my setup (which was purchased used to I kept my mouth shut) because the hose decided it liked the coolant on the outside more than on the inside.
I replaced mine while the trans was out.

Sent from my motorola one 5G using Tapatalk
 
biggy238 said:
While I agree with your sentiment, I'd be interested to know how many people have been down over the piss poor quality hose they packaged in those kits. I had to R&I my setup (which was purchased used to I kept my mouth shut) because the hose decided it liked the coolant on the outside more than on the inside.
I replaced mine while the trans was out.

Sent from my motorola one 5G using Tapatalk
Click to expand...

I would be more curious how the bypass became viewed as a necessary performance mod in the first place. Put this in the same category as aftermarket intake horns that go on top of the stock plenum.
 
Vincejax said:
I would be more curious how the bypass became viewed as a necessary performance mod in the first place. Put this in the same category as aftermarket intake horns that go on top of the stock plenum.
Click to expand...


To provide additional cooling to cylinder #6 was my reasoning. With the propensity of ring cracking on a stock 325 CR engine, I felt it was a wise decision. I did measure the temperature before and after and noted a difference.
However, my truck lives below 3,500 rpm.

What makes it an unnecessary modification?
 
I did not know that about the fleece kit, however knowing there was a t-stat back there I did not want to have to tear everything apart to get to it if it went bad so I went with a different kit that routed to the front with a different valve up by the upper radiator hose. Yes mine is stuck partially open, but to fix it at least I do not have to tear everything apart. It honestly does not bother me enough currently to fix it though.
 
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