6CTA Thermostat housing coolant leak

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Steelreaper80

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Does anyone know the part number for the thermostat housing gasket? I have a small but steady leak at the housing. I have included photos. Hard to tell what it is but the photos are directly behind the alternator mount. I have a heavy amount of rust in the system so I will be doing a flush along with a block heater and a coolant filter install. It may be covered in other threads but I do not have oil in my cooling system. Should I just dump the coolant, and run 3 bottles of Thermocure in the system then flush again and re-fill with heavy-duty coolant specifically for HD diesel engines that have all of the additives in it? Does anyone have any photos of where they mounted the coolant filter and where did they tie into the engine block for proper flow? I have seen a few other photos on putting the filter on the firewall to the right of the cab heater but that puts it directly above the exhaust pipe and I did not want all of the heat directly below the new filter. Thanks guys!
 

fpchief

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If you dont buy the high dollar fleet antifreeze, make sure you go with a low silicate green antifreeze and use the SCA additive unless your coolant filter you are using gives it the charge it needs. Do not buy test strips. I have one in will mail you for free when it is time for it. I bought a bottle of them and wont use them all.....ever.
 

74M35A2

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Use the Cummins Quickserve website. Works amazingly perfect to find all of the correct Cummins part numbers, even for our military engine serial numbers. Free. You can the snag them from Amazon or obtain from any local dealer.
 

charlesmann

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according to the ipc. dual thermostat housing with internal bypass, item #8 for under the filler neck, p/n 3060912 NSN 5330012721142
item # 11 for under the housing p/n 3914310 NSN 5330012878656

for external bypass, # 23 under the neck, p/n 3913032 NSN 5330013011828
item # 28 under the housing p/n 3913025 NSN 5330013020780
 

charlesmann

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Temple, Tx
Does anyone know the part number for the thermostat housing gasket? I have a small but steady leak at the housing. I have included photos. Hard to tell what it is but the photos are directly behind the alternator mount.
where you able to locate the gaskets needed? if so, where did you find them? I'm striking out with the surplus sites, including local parts stores.
 

simp5782

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You will have to order any parts for the 6cta from cummins or a diesel parts place like dieselpartsdirect.com in baton rouge will have the cheapest prices
 

charlesmann

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You will have to order any parts for the 6cta from cummins or a diesel parts place like dieselpartsdirect.com in baton rouge will have the cheapest prices
thanks for the link. they had all but the shutter stat. maybe I'm looking it up wrong, but there are only a few alt. p/n when looking it up by nsn or p/n.


For ALL to comment on, not meant only for simps for the below comment.

before i left for work weeks ago, i had an overheating issue, coolant was low. i serviced it and it worked fine. came home, used the cane and set the rpm to 1600 and i kinda overheated it again. i sprayed the eng down with water till the temp dropped below 180, fired it up and as long as i idled the eng, and kept the hose on it, it didn't get above 180.
went back and re-read this thread, esp for the shutter stat, and fired it up, and decided to ck the surge tank and it was 2 gallons low.
where on earth is the coolant going in a semi sealed system? i see no signs of leaks, yet i did drain the entire system, did a wash and flush, and have topped of the system 4 times since the initial servicing after the wash/flush. i did open the petcock for the after cooler for the initial servicing and for each topping off of the system.

also, what is the best solution/chemical to completely or as near to completely, clean the system of rust? coolant aint cheap and i don't want to keep draining and filling with coolant for each time i see rust colored fluid. after my initial servicing after wash/flush, the fluid was flowing through mostly green, now its back to rust colored, no tint of diluted green.
 

silverstate55

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also, what is the best solution/chemical to completely or as near to completely, clean the system of rust? coolant aint cheap and i don't want to keep draining and filling with coolant for each time i see rust colored fluid. after my initial servicing after wash/flush, the fluid was flowing through mostly green, now its back to rust colored, no tint of diluted green.
Cascade dishwasher detergent (for use in dishwashers, other soaps will suds up too much) and distilled water. Heat it up good by driving her around and let it sit for a day, then flush with fresh water/distilled water.

If that doesn‘t get all the rust out, then do a flush with 50/50 mix of white vinegar and distilled water, then flush thoroughly with fresh water until not a hint of vinegar remains in water. I always remove the thermostat before flushing & replace it afterwards with a new one, but that’s just me.

Your overheating could be due to an inop fan clutch, as mentioned with the shutter stat replacement... however, when I changed mine out due to overheating, I found that when I disconnected the air hose to the fan clutch, at both ends it had brass elbows with tiny mesh screens in them...the screens were clogged with gunk due to the air dryer not being serviced for so long before I bought the truck. When the air dryer is clogged due to lack of service, all kinds of crap can bypass the dryer and go right into the compressed air system. It took me several years to fully purge & clean crap out of my compressed air system/lines/components.

In any event, my screens in the elbows were so clogged that no solvent could penetrate them so I replaced them. I got all my hoses & fittings at a Parker affiliate so they had them in stock.

As for your missing coolant, if it’s not going into your crankcase, it will take some investigating time to figure out where it’s going.
 

charlesmann

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@silverstate55
I did the cascade and flushed till i had no hint of brown/rust. I flushed the sys by by running the hose in the rad intake and letting the eng push the junk out till clear water flowed out.

i’ll try the vinegar since its cheaper and less caustic than clr.
Not sure what/why the shutter stat would affect the cooling ability. It locks the fan clutch and causes it to spin seconds after firing the eng up and as a previous member said, robbing power from the eng. If i disconnect the inlet or outlet from the stat, the clutch unlocks and can be stopped by hand.

It doesnt seem to be leaking in the crank since my oil lvl has not changed.
im guessing i didnt fill it completely and im still having to top it off. yesterday i added another gal of AF and 1.5 gal of water.
I do plan on replacing the thermostat, gaskets and the water pump. I will dig in the other thread about rebuilding the shutter stat but the pump and thermo will be first.

Thanks for the info.
 

Steelreaper80

Member
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8
Location
Indianapolis IN
where you able to locate the gaskets needed? if so, where did you find them? I'm striking out with the surplus sites, including local parts stores.

I did. I used my engine serial number on parts.cummins.com and got the part number. Just like Wes said, I ordered it online. It was cheap. Shipping was $3.00 more than the part.....

I also noticed my water pump was leaking. I ordered one of those as well. I have an oil leak on the driver's side of the engine I just can't seem to find. Seems like it is over the front axle. I tightened the hose clamps but still have a leak. It dumps about a half a cup of oil at shut down.
 

74M35A2

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Could be front crank seal or timing cover gasket. Mine were leaking. Did both same time in a parking lot with only 2 tools. Very quick and easy to change.
 

silverstate55

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I have an oil leak on the driver's side of the engine I just can't seem to find. Seems like it is over the front axle. I tightened the hose clamps but still have a leak. It dumps about a half a cup of oil at shut down.
Since most of these trucks run 10w oil in the power steering system, are you sure it’s engine oil and not power steering oil? I had an issue with my PS pump leaking in the same spot; I replaced every hose & replaced the pump reservoir O-rings, but it still leaked from the bottom of the reservoir....so I sealed up the bottom of the reservoir with gasket maker, PROBLEM SOLVED. Plus I flushed out the 10w oil and now run PS fluid; works like a champ.

Just a thought...
 

charlesmann

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Temple, Tx
Since most of these trucks run 10w oil in the power steering system, are you sure it’s engine oil and not power steering oil? I had an issue with my PS pump leaking in the same spot; I replaced every hose & replaced the pump reservoir O-rings, but it still leaked from the bottom of the reservoir....so I sealed up the bottom of the reservoir with gasket maker, PROBLEM SOLVED. Plus I flushed out the 10w oil and now run PS fluid; works like a champ.

Just a thought...
X2,
I gave truck a bath, cleaning everything i could get to with a pressure washer or a pump up sprayer in more delicate areas after soaking with a biodegradable petroleum eater. I soon noticed my PS pump reservoir was puking out of the dipstick port.
 

Steelreaper80

Member
97
1
8
Location
Indianapolis IN
Since most of these trucks run 10w oil in the power steering system, are you sure it’s engine oil and not power steering oil? I had an issue with my PS pump leaking in the same spot; I replaced every hose & replaced the pump reservoir O-rings, but it still leaked from the bottom of the reservoir....so I sealed up the bottom of the reservoir with gasket maker, PROBLEM SOLVED. Plus I flushed out the 10w oil and now run PS fluid; works like a champ.

Just a thought...

It might be that, but I haven't really noticed a drop in fluid level. I will be back at the shop on Monday. I will absolutely check it. I have also heard of the injection pump leaking. Could it be that also?
 

charlesmann

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Location
Temple, Tx
Well, rebuilt the shutter stat and it work for bout 30 sec, compared to the 2-3 sec prior to rebuild.
im guessing a new 1 will put on order.

I took the tck out for spin around the country block and temp never got above 180-190, but im guessing the fan being on engaged the entire time contributed to the low temp.
About 1/4 the way back, i could smell something like burning rubber (thinking a flat tire or rad hose). Limped it hm, checked everything and no more smell. Topped the coolant tank off and took another trip around a different block. The smell came back and i sniffed it down to the power steering fluid being puked everywhere.

Didnt someone say that fluid is atf fluid?
 

simp5782

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Well, rebuilt the shutter stat and it work for bout 30 sec, compared to the 2-3 sec prior to rebuild.
im guessing a new 1 will put on order.

I took the tck out for spin around the country block and temp never got above 180-190, but im guessing the fan being on engaged the entire time contributed to the low temp.
About 1/4 the way back, i could smell something like burning rubber (thinking a flat tire or rad hose). Limped it hm, checked everything and no more smell. Topped the coolant tank off and took another trip around a different block. The smell came back and i sniffed it down to the power steering fluid being puked everywhere.

Didnt someone say that fluid is atf fluid?
All fluids should be 15w40 or 10wt from the military except axles and transfer case

Horton thermal sensor and solenoid will solve all shutterstat issues for good.
 
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