Ok to drive with t-stat stuck open? - Dodge Diesel

zgoober · 02-07-2011, 02:46 PM

Pretty sure my thermostat has been stuck open for the past 3 months. Truck doesn't get above ~150 degrees.

Has this, or will this, have any negative side effects? Major or minor?

67HotRod · 02-07-2011, 03:04 PM

Besides lower mpg, I could see carbon buildup..

SIXSLUG · 02-07-2011, 03:23 PM

I changed mine out as soon as I noticed my temps were below normal.

carl48 · 02-07-2011, 05:44 PM

more engine wear

m.t.hands · 02-07-2011, 09:44 PM

the "seal" broke on mine and was holding it open, takes all of ten minutes to change it out....i went with a napa, but i think most suggest finding a cummins replacement....

zgoober · 02-08-2011, 08:07 AM

Yes, I have replaced the thermostat.

I can find information about thermostats failed closed and the I'll effects of overheating. I can't find much about failed open. At least nothing specific...

Carbon build up? Where? Is that serious?
Engine wear? Why? Where?

rickf · 02-08-2011, 08:48 AM

One of the byproducts of combustion is sulfur dioxide, not as much now with USD but still there. When mixed with the condensation in an engine you get sulfuric acid. I don't think I need to say that is bad. When an engine does not get above 180 degrees then the water does not evaporate out of the crankcase and you have the acid formation. Plus diesels run better the hotter they are.

Rick

m.t.hands · 02-08-2011, 10:02 AM

i would think you'd experience incomplete and poor cumbustion, leading to higher carbon deposits in the valve-train

zgoober · 02-08-2011, 12:54 PM

Thanks. Good information to know, but not so great to hear. Will running any additive in the fuel or oil clean this up?

ellerman · 02-08-2011, 01:07 PM

Zgoober, change the thermostat and if you are worried about an excessive amount of acid that could have built up change your oil. If you are worried about carbon run the truck hard or tow something heavy. I doubt you did any damage.

gator_grabber · 02-08-2011, 04:30 PM

I'd highly suggest you attempt to get a Cummins thermostat, the aftermarket ones just don't perform as well. BTW, running an engine too cold is really hard on it and causes accelerated wear.

totalloser · 02-09-2011, 08:08 PM

+1 to cummins stat. Usually fails open. This is pretty rare with normal stats. Opens abruptly causing temp fluctuations, but has much bigger port.

IMO the main issue is the terrible fuel efficiency. But as to unhappy engine from running cold, the pistons will never get to op temps, and will remain tapered instead of swelling up to fill the bore. Potentially a little more wear on pistons, but I wouldn't worry much about it.

You are probably losing about 3mpg running at that temp. Add it up... ouch!

Midnite · 02-10-2011, 02:11 PM

Zgoober, I guess I'll be the lone dissenter here. I don't think you've suffered any engine damage whatsoever. I also don't believe the mileage difference is much at all, at least in my experience with a failed thermostat. It certainly wasn't noticeable in my case.

It's not like the engine is remaining at the same temperature as the surrounding environment. Even with a failed thermostat the engine gets up to 100 degrees fairly quickly, it just starts to taper off and take progressively longer to reach higher temps.

02-07-2011, 03:04 PM	#2
67HotRod Registered User Join Date: Feb 2005 Location: Franklin County Missouri Posts: 1,132 My Photo Gallery My Classified Ads	Besides lower mpg, I could see carbon buildup.. __________________ Tow Vehicle: 2001 Dodge Quad cab, 3/4 ton 4X4, 3.54's running 285's with auto. Towing & camper option. 2" level kit, BHAF, AirDog, 180 STAT, 4"exhaust, Goerend bros TC/VB, BW trans. Edge Comp, rv injectors, deep trans pan, Boost/Pyro/Fuel/trannny gauges. 250K miles

02-07-2011, 03:23 PM	#3
SIXSLUG Registered User Join Date: May 2006 Location: Pacific NW, B'ham, Kalispell MT Posts: 3,491 My Photo Gallery My Classified Ads	I changed mine out as soon as I noticed my temps were below normal. __________________ Kurt 2001.5 2500 QC LB 4WD H.O. 6-SPD SLT Plus 3.54's, Camper/Tow/Plow, A.R.E. Canopy w/ SS Vanguard rack, Southbend clutch and hyd.,TIMBO APPS, BHAF/Heatshield, MBRP 4" TBE, FP Gauge, Femco E-Z Drainplug, DSS, Thuren Trac Bar, 2" leveling kit, P/H Tow Mirrors, PBR, 128K miles. FASS LP "When I was younger I could remember anything, whether it happened or not." Mark Twain Support Our Troops! NRA, MSBL, BYO, GSP, BOLTS, Southpaw, CDC* *Cracked Dash Club

02-07-2011, 05:44 PM	#4
carl48 Registered User Join Date: Feb 2008 Location: ruidoso new mexico Posts: 1,374 My Photo Gallery My Classified Ads	more engine wear __________________ 06 3500 4X4 dually qc G56 dynatrac free spin fitch fuel catalyst BD exhaust brake donaldson m90535 muffler, cfm+, winspeed heater delete, smarty jr 750 luberfiner bypass filter taylor wings, psm air, cool hose, tag, air tab's, reese 20k 5th wheel, pdr cam,ddp50 hp injectors

02-07-2011, 09:44 PM	#5
m.t.hands Registered User Join Date: Dec 2004 Location: n. alabama Posts: 56 My Photo Gallery My Classified Ads	the "seal" broke on mine and was holding it open, takes all of ten minutes to change it out....i went with a napa, but i think most suggest finding a cummins replacement.... __________________ 2001 QCSB 4X4, auto, fass pump, gauges, otherwise stock, will be tuning up some soon!!!! things are more like right now than they've ever been

02-08-2011, 08:48 AM	#7
rickf Registered User Join Date: Oct 2010 Location: Pemberton NJ Posts: 445 My Photo Gallery My Classified Ads	One of the byproducts of combustion is sulfur dioxide, not as much now with USD but still there. When mixed with the condensation in an engine you get sulfuric acid. I don't think I need to say that is bad. When an engine does not get above 180 degrees then the water does not evaporate out of the crankcase and you have the acid formation. Plus diesels run better the hotter they are. Rick __________________ 1998 Dodge Ram 3500 2 WD Quadzilla XZT 75 gallon in bed transfer tank. Location, 08015, NJ.

02-08-2011, 08:07 AM	#6
zgoober Registered User Join Date: Nov 2006 Location: Dallas, TX by way of Lubbock Posts: 11 My Photo Gallery My Classified Ads	Yes, I have replaced the thermostat. I can find information about thermostats failed closed and the I'll effects of overheating. I can't find much about failed open. At least nothing specific... Carbon build up? Where? Is that serious? Engine wear? Why? Where?

02-08-2011, 10:02 AM	#8
m.t.hands Registered User Join Date: Dec 2004 Location: n. alabama Posts: 56 My Photo Gallery My Classified Ads	i would think you'd experience incomplete and poor cumbustion, leading to higher carbon deposits in the valve-train

02-08-2011, 12:54 PM	#9
zgoober Registered User Join Date: Nov 2006 Location: Dallas, TX by way of Lubbock Posts: 11 My Photo Gallery My Classified Ads	Thanks. Good information to know, but not so great to hear. Will running any additive in the fuel or oil clean this up?

02-08-2011, 01:07 PM	#10
ellerman Registered User Join Date: Feb 2005 Location: Chula Vista, Ca Posts: 348 My Photo Gallery My Classified Ads	Zgoober, change the thermostat and if you are worried about an excessive amount of acid that could have built up change your oil. If you are worried about carbon run the truck hard or tow something heavy. I doubt you did any damage. __________________ 2012 4x4 3500 CCLB Laramie Max Tow 2001 4x4 QCLB Sport 6spd HO, Carli- Arms, Coils, Billet shock towers, sway bar links & 3rd gen track bar, 3" Sway-A-Way shocks, Deaver 12 leaf spring packs, long travel air bags, Defiant dual stabilizer, 3rd gen wheels & brakes, 295/70R17 Toyo MT's, Centramatic wheel balancers, Edge Juice with Attitude, FASS, MBRP 4", AFE stage 1, RV275's, Jacobs Exhaust Brake, DSS steering stabilizer, Luke's links, Southbend ConOFE, Optima Yellows, Royal Service body

02-08-2011, 04:30 PM	#11
gator_grabber Registered User Join Date: May 2006 Location: Gainesville, FL Posts: 190 My Photo Gallery My Classified Ads	I'd highly suggest you attempt to get a Cummins thermostat, the aftermarket ones just don't perform as well. BTW, running an engine too cold is really hard on it and causes accelerated wear. __________________ 1999 Dodge Ram 2500, QC/SB, 2WD, auto, RV275s, Edge w Attitude, AFE Stage 2, AirDog 150, BioDiesel, Bilstein Shocks (B46-1907 & 1908), B&W turnover hitch, Firestone airbags, RDS toolbox/60 gallon tank combo, Sport headlight conversion with HD wiring, Bosch Compact 100 fog lights 1996 Dodge Stealth RT/TT

02-09-2011, 08:08 PM	#12
totalloser Registered User Join Date: Jun 2008 Posts: 483 My Photo Gallery My Classified Ads	+1 to cummins stat. Usually fails open. This is pretty rare with normal stats. Opens abruptly causing temp fluctuations, but has much bigger port. IMO the main issue is the terrible fuel efficiency. But as to unhappy engine from running cold, the pistons will never get to op temps, and will remain tapered instead of swelling up to fill the bore. Potentially a little more wear on pistons, but I wouldn't worry much about it. You are probably losing about 3mpg running at that temp. Add it up... ouch! __________________ '01 dually 100hp tips ez elbow boots 4"exh/brake big shaft nv5600 Valair manual CAD LSD BDbrace 1.5dom Delphi tapped &rammed ps ported/shimmed 265/70r19.5 AF big rigs 3rd gen brakes Ugly black and thrashed.

02-10-2011, 02:11 PM	#13
Midnite Registered User Join Date: Jul 2004 Posts: 528 My Photo Gallery My Classified Ads	Zgoober, I guess I'll be the lone dissenter here. I don't think you've suffered any engine damage whatsoever. I also don't believe the mileage difference is much at all, at least in my experience with a failed thermostat. It certainly wasn't noticeable in my case. It's not like the engine is remaining at the same temperature as the surrounding environment. Even with a failed thermostat the engine gets up to 100 degrees fairly quickly, it just starts to taper off and take progressively longer to reach higher temps.

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