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Thermostat replacement..

diesel4me

diesel4me

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What are the chances the 2 bolts holding the thermostat housing on,will come out without busting off in the water outlet pipe casting,when they haven't been touched by me since I got the truck in '03,and likely years more before I ever saw it ?..

Getting only lukewarm heat lately,and the gauge only goes a tad past 100 degrees,I've already tried grounding the sending unit wire and it pegged the gauge,so I assume the gauge works OK (always did),and the sending unit is "probably" still good,since the engine just doesn't seem to be reaching its usual operating temperature..

The only thing I've done to the cooling system on this engine was add maybe 3/4 of a gallon of coolant 6 months ago--it has always had the coolant level about 3" down from the cap previously, and hardly any in the overflow jug since I've owned it,I decided to top it off during the summer when we had an extended period of 90+ degree humid days here..it wasn't till a few weeks ago I noticed the gauge reading was lower and the heat wasn't that great--up until then the weather was still mild enough not to need the defroster or heater much...

The radiator has a lot of dead leaves piled up along the bottom behind the grille,and the plow hoses let some ATF get on the core,so some of it is "sludgy" with a greasy build up...but the thing is so huge ,I guess it doesn't phase it,its never overheated since I've had the truck..

I dont even know if there IS a thermostat in it,but I assume there is because it used to get good heat,it must be sticking partly open ..
It figures the near complete parts 6.2 engine I have is missing that water outlet crossover pipe the thermostat goes in...this practically guarantees I'll have trouble with the bolts breaking off--if I had a "spare" I'd never have to use it..

It appears the thermostat for the 6.2 is a weird size,one that nothing else in the past 40 years uses,I'm going to dig thru my boxes of left over OEM parts,I know I had a few thermostats for old Mopars and Buicks new in the box that are the same,IF they are still around and I can find them..

I assume a 195 degree thermostat is OEM temperature ?...far as I can tell looking one up online that is what the listings say..I wouldn't put anything lower than a 180 in it ,being a diesel..

I'll have to move a ton of :poo: in my garage to get my torches out,I know these bolts will likely break off without heating the casting up good first..not looking forward to this job--or any of the others the truck needs...might snow here tomorrow night,in a way I'm tempted not to touch it right now..:mad1:
 
Yeah , the bolts look to be 10MM ,they have 15mm hex flanged heads,so I'm hoping they are that thick,that may give me a better shot at getting them loose without them breaking...

The casting they screw into is only die cast crap though..that might break off instead...I'm going to heat it up as much as I dare before I try loosening the bolts..

I haven't seen any 6.2's in the junkyards here lately,so if I needed that part I'd be S-O-L ..

I think I'm going to leave it alone until after this weekend,I am not planning on driving it more than 10 miles,and if it snows enough I may need to put the plow on it..so far they are only predicting 1" or so in my area,but I've seen that end up being a foot more than once this time of year here before..
 
Actually the '85 Burb came with one of those grill covers that snap on...maybe I'll end up using that for now..but I'd have to add snaps to the truck or zip tie it on..
 
Spray a bunch of pb blaster on the bolts! A little heat from like a plumbers torch is more then enough.

As for a spare. I might have one amongst my collection of parts down at my FL house. I can ask my dad to look for it. Actually @AugustDiesel might have his old one since he changed over to a serpentine setup.
 
I am most likely not going to attempt replacing the thermostat until I have a spare crossover located "just in case"...
I know of one G-10 Van in a junkyard with a 6.2 ,but the crossover on a van might not be the same--and they may not want to let me take parts off a complete engine..(and will the bolts come out of that one after sitting 20+ years ?)..

After reading numerous posts on other diesel forums saying their crossovers broke like glass when they went to remove the bolts,or broken bolts out of it after taking it off the engine,or bolting it back onto the heads--I'm reluctant to chance that happening and leaving me without a vehicle for an extended period of time,when this is the season I need it the most..

I'm getting very tired of the 6.2--seems like everything on it is some crap design,with NLA parts when you end up needing something like these crossover housings..and I hate the layout of the whole engine,period..like it taking a day to replace valve cover gaskets when I could do them on a SBC in 20 minutes..(and you'll likely ruin an old rusted injector line in the process)..hate to waste money & effort on it when it could spit the crank out after all that BS too..

This is just one more reason to get rid of it and put in a good reliable SBC or BBC...but the truck is rapidly getting to the point its not worth the effort now..
I just want to keep it going thru the winter..will suck not having good heat or defroster though..maybe blocking the grill off will help enough to get by..
 
I broke my housing on my 6.5 when I went to swap thermostats. But i was able to fix it so I could limp along till upgrading to a dual thermostat housing.
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but you can try maybe? I was cranking real hard (loosening) when mine broke. Some PB and heat might go a long way.
 
Yikes..that sucks..and I'd hate to have mine do the same thing..:doah:

Cheap pricks could have at least made the crossover out of cast iron or steel,at least then it could be brazed or welded back together..
This is why I hate "newer" vehicles,everything is crap die cast or plastic now..

Maybe after the threat of snow is over I'll attempt to mess with it..
I don't have a thermostat or a gasket yet for it either..

I've seen a few used crossovers online going for $75+ bucks.
I'd be reluctant to spend that much on a complete good running 6.2 right now.:surepal:

I'm wondering if using an air impact gun might stand a better chance of getting the bolts loose without busting them or the housing..a feather touch on the trigger,not a full blast..

I've read the single thermostat is actually better than the dual setup,not that I'd go looking for a dual crossover,that would need 2 thermostats..
Bad enough paying for one that "might" work ..todays thermostats tend to be crap brand new out of the box half the time..even 30 years ago half the ones I sold at the parts stores came back "defective",they either stuck open or closed --a few customers engines sustained major damage from overheating..
 
Dual thermostats work better but you need a restricted return fitting to send more coolant through the rad.
it sucks yours is giving you so many problems, my 6.5s been great so I’ve been doing tons of upgrades and work. Now I pull 12k when I go camping.
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Mine is just "old"--it was put in this truck before I got it,it isn't the original engine,don't know what year it might be from..but it has to be at least 30 years old I'd guess..probably sat in a salvage yard for years before it landed in my truck..

The thing runs OK when its got no bellyaches,and I dont really hate the 6.2,but I do hate working on it,mostly due to the design of the thing..

GM seemed to go overboard making things harder to repair ,like the water pump..
I much prefer the SBC-BBC style,4 bolts and your finished,you dont need to pull off the front of the engine..and coolant cant migrate into the crankcase on a SBC..
When the water pump starts peeing on this engine,I'll be more likely to start unbolting the engine from the truck,it is less bolts and labor to pull the engine out ,than bending over it for 2-3 days in my condition..

And there was no good reason to make the thermostat crossovers out of junk die cast crap other than to save then 10 cents per engine..

GM could have at least kept making replacements longer than 10 years..and using a cast crank was their biggest mistake..hell,they had 283's with forged cranks,you'd think a diesel would demand one..the blocks were not beefy enough either..

Most agree the 350 Olds based diesel was GM's "worst",but many say the 6.2 is a close second..after the damage GM's reputation suffered after the 350 diesels started dying young,you'd think they would have designed the 6.2 to be bullet proof..but they didn't..

I have friends who had 6.2's that ate one head gasket after another and had cracked heads too,I'm fortunate so far mine has not blown one ..(that'll be next ?)..
They were smart and put 350's in their trucks after being disgusted with the diesels..after wasting hundreds of bucks fixing the 6.2's.

Overall the thrill and novelty of having a diesel powered square body has long worn off,and I'm wishing now I had just yanked it out when I bought the truck in 2003 and sold it to someone else,let it be their headache..
I had a good running 400 SB back then out of my previous plow truck,and several other SBC engines I could have had cheap then to put in it,and it would have started without grief every cold day after a blizzard,with no block heaters,batteries needing to be boosted with a charger all night prior to the storm,and gas is cheaper too--truck has never got more than 15 mpg or so,I've had gas V8's that did as good..

I've put 3 starters and 3 sets of 8 glow plugs in this engine plus a few more new ones after some expired or rusted away,a total of about $400 for "good used" starters and new glow plugs..could have tuned up a gas engine several times with that amount of money,and still have the original starter too probably..
God forbid an injector pump ever craps out..that'd be at least $400 ,money better spent buying a SBC with..

I'll be highly unlikely to ever own another diesel vehicle--they are fine if you live down south and you drive long distances often..or need to pull heavy loads..

I don't,and now that I'm a "senior citizen" I rarely travel far from home,diesels don't like being started up and driven 2 miles to Walmart and the pharmacy and shut down again--that eats glow plugs and starters up all too soon..it's not good for any engine really,but especially a diesel..
 
@diesel4me ive got your replacement crossover. Good shape too. Was NOS when I bought it and ran it for maybe a year before I swapped to the dual tstats

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I'll PM you if I end up needing it..
It looks a bit different than the one on my engine,mine lacks the sensor port,but maybe its overall the same otherwise,from what I've read there are a few different styles depending on what the engine was installed in (van,P-30,humvee,etc).....
I do not know the exact year the engine is,or what it came from ,its not the original one...

I noticed there are thermostats you can get that install in the radiator hose--was thinking that might be one way to keep the thing running if I do break the crossover trying to get the bolts out..cut off the portion where the thermostat was and put a radiator hose to join the two pieces back together and use that style thermostat--or none at all,if I was in a bind like needing it to run to plow with..
 
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