6.5L k3500 getting hot all of a sudden

[Angelo]

Sure sounds like time to switch thermostat brand. Motorad has been a trusted name for a long time (I hope that hasn't changed) - Motorad 423195 should be the correct one for you. Also 7332195 is their fail-safe design, but in the case of the 6.td even failing open may not be enough to save your engine, so next up, please consider...

Since your application is a heavier-than-normal vehicle: https://www.thedieselpage.com/features/dualstats.htm - though it'll cost you. It just might save you the expense of total engine replacement, though. You probably already know about this upgrade, but if you haven't read this particular article, please do. Heavy trucks like ambulances are specifically mentioned as to why this upgrade was engineered by GM.

Richard

Thanks for the info. Looking to see if it will bolt on without much if any modification to my truck. I have dual alternator as well so I wonder if there will be space.

These 2

96-02 GMC Chevy 6.5L Turbo Diesel - Dual Thermostat Housing Crossover 12553405 | eBay

Find many great new & used options and get the best deals for 96-02 GMC Chevy 6.5L Turbo Diesel - Dual Thermostat Housing Crossover 12553405 at the best online prices at eBay! Free shipping for many products!

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And

1996 - 2002 GMC CHEVROLET 6.5L TURBO DIESEL DUAL THERMOSTAT HOUSING P/N 12553405 | eBay

Find many great new & used options and get the best deals for 1996 - 2002 GMC CHEVROLET 6.5L TURBO DIESEL DUAL THERMOSTAT HOUSING P/N 12553405 at the best online prices at eBay! Free shipping for many products!

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Look like they will bolt right in. Does that sound right?
And I'm already seeing coolant seepage out of the new gasket, from the high flow WP I guess.That would explain it according to that article .

 

[someotherguy]

My 6.5td experience is limited mostly to walking/pushing/towing, and telling my past customers at the salvage yard that I don't have any good engines.. but.. yes, it sounds like the whole package is the only way to get reliable, better cooling. Double thermostat housing, high flow water pump, and the fan upgrade as well.

Richard

 

[Schurkey]

Also 7332195 is their fail-safe design, but in the case of the 6.td even failing open may not be enough to save your engine, so next up, please consider...

Those thermostats DO NOT "fail open". They are intentionally advertised in a deceptive manner, making it seem like they're something that cannot fail "closed".

They LOCK open when SOMETHING ELSE fails, and the engine gets hot. Then you throw it in the scrapmetal bin because it won't ever close again. It's "done" when it locks open.

A non-defective thermostat fully opens when the engine gets hot; and when the engine cools off, it'll close and continue to operate as normal.

The "Fail-Safe" thermostats are a gigantic fraud and waste of time, money, effort, enthusiasm, and resources.

From the Motorad web page:

MotoRad Fail-Safe® Thermostats

Motorad Fail-Safe Thermostats, are designed to prevent engine overheating & provide peace of mind on the road. Upgrade to Motorad Fail-Safe Thermostats for dependable temperature regulation and worry-free driving.

motorad.com

Stage 2
When overheating is caused by a deteriorating cooling system part, the fail-safe has a secondary stroke that activates a precision engineered piston. This automatically locks the valve into a wide open position to allow coolant to circulate freely.


Note that once the fail-safe thermostat has locked in the open position, it cannot be used again and must be replaced.

 

[someotherguy]

Those thermostats DO NOT "fail open". They are intentionally advertised in a deceptive manner, making it seem like they're something that cannot fail "closed".

They LOCK open when SOMETHING ELSE fails, and the engine gets hot. Then you throw it in the scrapmetal bin because it won't ever close again. It's "done" when it locks open.

A non-defective thermostat fully opens when the engine gets hot; and when the engine cools off, it'll close and continue to operate as normal.

The "Fail-Safe" thermostats are a gigantic fraud and waste of time, money, effort, enthusiasm, and resources.

From the Motorad web page:

MotoRad Fail-Safe® Thermostats

Motorad Fail-Safe Thermostats, are designed to prevent engine overheating & provide peace of mind on the road. Upgrade to Motorad Fail-Safe Thermostats for dependable temperature regulation and worry-free driving.

motorad.com

Yeah, I understood the method behind their operation (locks open, dispose) so I wasn't really suggesting its use in terms of thermostat failure but just cooling system issues in general, since it's a 6.5td. His AC Delco thermostat failed super-prematurely and I don't expect a Motorad to do the same, but I could be wrong. I'd bet the AC Delco is China-made trash like a lot of their stuff is now; no idea on the Motorad. I hope their stuff hasn't turned to junk, too.

Richard

 

[Orpedcrow]

Could be the angle of the photos, but I didn’t see the fan shroud. Make sure you have a complete shroud.

 

[Schurkey]

I'd bet the AC Delco is China-made trash like a lot of their stuff is now; no idea on the Motorad. I hope their stuff hasn't turned to junk, too.

Motorad = Made in Israel.

The Motorad in my truck (new last fall) needs a few cycles before the temp stabilizes--up to 220, down to 170. Up to 210, down to 180...eventually it hangs steady at 195--200.

 

[454cid]

Motored is often from Israel, but I've seen other coo too. Some stuff should be US made since they bought stant....I'm hoping that plant is still running. I'm seeing less of the stant brand, so I'm guessing it's being phased out.

 

[Angelo]

Could be the angle of the photos, but I didn’t see the fan shroud. Make sure you have a complete shroud.

It's cooling perfectly now with the new 190° t stat

 

[Orpedcrow]

It's cooling perfectly now with the new 190° t stat

I’d still make sure you have a complete shroud, we haven’t hit summer yet.

 

[Angelo]

I’d still make sure you have a complete shroud, we haven’t hit summer yet.

It was cooling fine the past year thru the past 2 summers with the same t stat. @Orpedcrow I should have mentioned those pics were taken with the upper shroud removed! Sorry. Thanks for sharing