Head Gasket

[6.5 Detroit Diesel]

So i just replaced the thermostat after blowing the gaskets out.

truck was doing good for a day or two. now it will occasionaly spike in temperature. it will almost go into the red (125C) and then drop. while it climbs high, the heat doesnt work.

i thought it was a air bubble, and bled the system twice from the valve above the thermostat. both times, i got a lot of air out.

i have refilled the overflow, and yet it keep on going really high temperatures, like an air lock, and then dropping down and reading low coolant. no smoke out the exhaust, truck idles and runs fine. im starting to wonder if this is either a bad thermostat, or a head gasket pressurizing the system.

[john8662]

What kind of thermostat? High Flow or standard (high-flow is the factory OEM one, looks different from the standard Murray or Stant stat).

Single stat?

Are you losing coolant?

I'd suspect thermostat, a sticking one at that.

[Kennedy]

Sounds like air in the system. Most likely combustion gasses I'm sorry to say.

When teh heater swings and temp gauge roller coasters it's typicl head gasket. Your "couple days" of operation should have purged the air from the refill.

Are you sure you got the heads and deck clean and had no serious erosion?

[6.5 Detroit Diesel]

the thermostat was a stant one. just a single setup.

after refilling the overflow, it will heat up and then when i stop the engine, it will dump a bunch out the overflow.

the low coolant light will come on and off at random it seems.

the old one never did this, i just replaced it while i had the thermostat assembly apart.

i cleaned all the gasket surfaces and used new gaskets.

if it is the head gaskets, then i will probably try to do them ASAP and beat the problem before it kills the engine.

once the temperature spikes and then drops, the truck runs at the proper temperature after that.

i am really hoping that it isn't the heads. money is rather tight right now. :(

[JohnC]

once the temperature spikes and then drops, the truck runs at the proper temperature after that.

If that's the only issue (and the heater works through it all) and you're not still getting air out of the system, then it sounds like a sticky thermostat. If it's still getting air bound, well.... If the heater stops working as the temp climbs it's almost certainly getting air bound.

[6.5 Detroit Diesel]

When it spikes in temp, the heater will sometimes blow cold, other times blow warm

[Ms54Coupe]

I heard that if you overheat a thermostat once it can destroy it...perhaps a new thermostat is in order (frustrating but better than another set of head gaskets)

[JohnC]

Does the thermostat have that little bypass foot on it? If so, maybe opening all the way in response to the temp spike could cut off the heater. If not, I'm betting on an air lock. If the system still "makes" air then something's amiss.

[Kennedy]

The bypass "foot" simply blocks the bypass forcing the coolant to go through either the radiator or the heater versus having 3 potential routes when open.

[jerry598]

If a t-stat doesn't fix it, then it's the head gasket for sure. Same symptoms I had for my blown gasket, resulted in a rebuild but only because the engine was already shot. If the rest of the engine is OK, just replace the head gaskets. Be careful and get them right this time. Check the heads for warping and/or cracks, and the block deck also to make sure you have a good fit between the two. Good luck.

Now have 5500 miles on my rebuild but it still burns some oil = disgusted in another thread.

[CedarGrove]

I went through this a few years ago. Same symptoms. Replaced heads and gaskets and the problem continued. Had a cracked block. Hopefully your situation is not this severe but I do think you should brace for the worst while hoping for the best.

Replaced the engine with a rebuilt number from Kennedy 50k ago (miles not $). I am very happy with everything.

[Kennedy]

Could try the old tried and true procedure suggested here on TDP years ago by MP.

Remove the belt and the tstat housing and start engine. Watch for air bubbles...

[6.5 Detroit Diesel]

Could try the old tried and true procedure suggested here on TDP years ago by MP.

Remove the belt and the tstat housing and start engine. Watch for air bubbles...

never heard of that, but, if i am pulling apart the housing, i might as well give it a try

[Yukon6.2]

Hi
Pulling the crossover works great,used it twice,once for a cracked head on my 6.2,and once for my 6.5,small bubbles on driverside,swaped the motor with a used one.Havn't pulled that one apart to see what was wrong yet.But it was doing what yours is.
Hope you don't see bubbles.
Good Luck
Thomas

[6.5 Detroit Diesel]

it will probably have to wait until saturday. got around ten inches of snow over night, the most in years. ended up getting called out and sitting in a little cat skid steer for 14 1/2 hours. :o

[6.5 Detroit Diesel]

well, i think that it is the gaskets. today i noticed that at idle the truck was smoking lightly. smelled like a little oil was burning in their. also the check engine light came on and off a few times.

insurance is up in a few days, and i have the use of my buddies 95' halfer 6.5

i guess i will save up and do the head gaskets.

[6.5 Detroit Diesel]

finally did the removal today. swapped the turbo first. put a GM1 onto as we thought the original turbo was having issues. then pulled off the housing and belt and filled it up to almost the top. started her up and it was actually shooting small amounts of coolant out from the passenger side. still smoking lightly at idle. bolted it back together and let it run. started to overheat again.

so, i am debating whether to just try some Bar's in the system. know of someone who did, and was able to stall off doing his headgaskets for a year. so short on money that i won't be able to do the heads anyways for a good month. if i cant get it to limp by for a few months, then that would be okay.

[rameye]

Its most likely not going to work....if it does, it most likely wont last very long.

Start planning your project...

My .02

[6.5 Detroit Diesel]

yea, it's just that i am stuck driving a 91' cougar xr7 that sucks gas like crazy until i get a truck going. :(

[DaveBr]

If you are going to try a bandage solution for a temporary fix then I recommend that you try a product called Iron Tight. It is the best stuff that I know of.

[6.5 Detroit Diesel]

is that a local product?

[6.5 Detroit Diesel]

got the product, ended up calling into their tech line to make sure everything works out right.

flushed the system with water, and i mean flushed. by the time i was done, the water didn't have any greenish tinge at all. supposed to put it in with water only and let it run at a high idle for around an hour. then drain the water, open up the t-stat housing, drain plug, and coolant overflow and let it "cure" for at least 12 hours.

then get some further sealant that irontite has and dump that in with fresh coolant.

the tech seemed very certain that it would work. i guess we will find out tomorrow.

* while idling during the flush, the truck blew a little smoke, then once the engine was warmed up, it ran clear. :confused:

[JohnC]

drain the water, open up the t-stat housing, drain plug, and coolant overflow and let it "cure" for at least 12 hours.


Good luck! Drain plug is behind the engine mount. ;)

[6.5 Detroit Diesel]

sorry, should have said the radiator drain plug.

seemed to work so far. ran the truck around, let it run for a couple of hours.

no leaks, no missing coolant, no overheating, and no smoke out the tailpipe.

removed t-stat housing again, and used a blow dryer to send hot air down the passages. :D

let it cure, tomorrow around lunch i will get coolant in there and get her running.

if there was no more problems, this would definitely be a prayer answered.

have to see what tomorrow brings. ;)

[KallyI]

got the product, ended up calling into their tech line to make sure everything works out right.

flushed the system with water, and i mean flushed. by the time i was done, the water didn't have any greenish tinge at all. supposed to put it in with water only and let it run at a high idle for around an hour. then drain the water, open up the t-stat housing, drain plug, and coolant overflow and let it "cure" for at least 12 hours.

then get some further sealant that irontite has and dump that in with fresh coolant.

the tech seemed very certain that it would work. i guess we will find out tomorrow.

* while idling during the flush, the truck blew a little smoke, then once the engine was warmed up, it ran clear. :confused:

Where did you find it? The only dealers I could find were in the States. Also which specific products did you use in your engine? I would like to try it in my engine if I can locate the products.

[6.5 Detroit Diesel]

called my local parts supplier. it's part of the action auto chain.

the stuff i used was the irontite ceramic. when i refill, there is a secondary treatment as well i will be using.

[DaveBr]

Start calling parts stores in Dead Rear. I think NAPA carries it. I found it at Bowness Auto in Cow Town.

[6.5 Detroit Diesel]

Start calling parts stores in Dead Rear. I think NAPA carries it. I found it at Bowness Auto in Cow Town.

lol, i must admit dave, this is the first time i have seen it referred to by that name....... :D

[KallyI]

Yeah, I will be calling. We do have a couple of Auto Parts stores in Lacombe too:D
I try not to go to Dead Rear as much as possible.
Working nightshift this weekend cuts into my time to do wothwhile things!:D

[6.5 Detroit Diesel]

just thought i would update. with over two weeks on the truck since running the irontite, no overheating, no smoking, and no trouble codes. stuff seemed to work really well. i know it won't last forever, but it will last for a little while. :D