Blown headgasket or cracked block? Help?

[DrkZide]

Note: Truck is an 86 GMC 1/2 ton with a Chevy 350 that some kid swapped in. Originally a V6.

So a couple days ago the truck overheated. It was completely fine before then, temperature gauge was always at a rock solid 210* and ha been since I bought it in Sept. I had been having a problem with my heater not working though. I opened up the radiator and found it was almost bone dry. It took a little over two gallons to top it back off. The heater started working again and the engine was actually running way cooler (it was 4* outside and it was running at around 115*).

Now, on my way home from work the temp spiked all the way over to the hot side and would then come back down, then my heat went away again. I pulled over and low and behold, I was low on coolant (took a little over a gallon to top it off again).

The motor has always smoked a little out of the breather and I blame that portion on a lack of a PCV system and possibly a bad seal somewhere. Now there was much more smoke coming from under the manifold and coolant over my driver's side axle and some on the ground. I can't tell if it's coming from where the head meets the block or if it's coming from the block. I can't see a physical leak, just the evidence which makes me think it's being pushed out under load. The cooling system did seem to have some pressure behind it which also makes me think my radiator cap is bad since the overflow still had coolant even the the radiator did not.

What do you guys think?

 

[The Pumpkinator]

I'm no engine expert but here's what I know; If it feels really doggy under acceleration then it could be a blown head gasket, to make sure you should preform a compression test on each cylinder, 80-95psi should be normal depending on the engine mileage. Since your engine is overheating there's a possibility that the heads could be warped and will need to be sent out to the machinist along with the intake manifold to have them decked, and when the heads are off, you may want to check the pistons for black crud caked on them, that's usually a sign where the coolant is leaking into the cylinder. Hopefully the coolant leak is a simple fix, leaky radiator, blown out hose, or a freeze plug that popped out. Another thing to check would be to pull the thermostat housing and see if its plugged up with Bars Leak or something dumb like that. The only way that I know how to find a crack in the block would be a complete tear down of the engine and carefully inspecting the inside of each cylinder for a hair line crack. Hopefully it doesn't come to that

 

[NorCal_Chris]

drain the oil and see if it is milky as well as the other things already suggested.
Allthough leaking coolant into the motor causes a clean piston, not a dirty one.

 

[bradshawtech]

You were probably experiencing radiator freeze up due to the cold temps. You obviously have some sort of leak but If there isn't any milky/greenish evidence on the dipstick then I would drain the radiator and verify that you have 50/50 mixture of antifreeze and water.

The symptoms you described are very familiar to me as I used to live in the San Luis Valley in Colorado and those type of temperatures really mess with people when it get that cold outside.

 

[79bonanza]

my head gasket blew then the block cracked under where the gasket blew out in between two cylinders. hopefully it isnt that

 

[DrkZide]

Ok so the oil looks fine, the coolant also looks fine albeit it has some good pressure behind it after driving it. The lower radiator hose is not frozen but I still feel hard spots like there's something in there. I'm going to replace every hose I can find (any recommendations on some nice SS hoses?).

This is the area where most of the "smoke/steam" is coming from. I'm not sure what's there exactly but I'm assuming it might be where the head gasket is blown if it is that. The "smoke/steam" was significantly reduced after I did the ol' pepper in the radiator trick. I can at least get to work and back home without pegging the temp sensor now. This is my only means of transportation at the moment seeing as we have almost two feet of snow on the ground and my car gets stuck in the driveway.

The picture is huge so I made it a clickable thumbnail.

 

[Fordum]

I like the custom connector on the sending unit.
That bolt with the white around it is not loose is it?

 

[Fordum]

Oh, and you do know that a lot of those hoses have springs inside them to prevent them from collapsing under suction.

 

[DrkZide]

I like the custom connector on the sending unit.
That bolt with the white around it is not loose is it?

Yea, that busted off when I bought the truck and I haven't had a chance to replace it yet seeing as my attention has been focused on so many other repairs needed to this thing. The PO didn't take care of it at ALL.

Which bolt? They all have some white LOL I take it you mean the center bolt? I haven't checked, I'll torque it down tonight and see if that helps.

Oh, and you do know that a lot of those hoses have springs inside them to prevent them from collapsing under suction.

I did not know that. None of my previous vehicles had those.

 

[imiceman44]

Yea, that busted off when I bought the truck and I haven't had a chance to replace it yet seeing as my attention has been focused on so many other repairs needed to this thing. The PO didn't take care of it at ALL.

Which bolt? They all have some white LOL I take it you mean the center bolt? I haven't checked, I'll torque it down tonight and see if that helps.



I did not know that. None of my previous vehicles had those.

Oh if your hose doesn't have the spring inside it will collapse and give you erratic temperatures.
Change the hose with a new one with spring or try and find a spring that fits inside it, you will see a huge improvement in stable temps.

 

[bradshawtech]

Based only on what I saw in the picture I am going to say that the head is cracked in the water jacket and is leaking fortunatly to the outside.

If the pepper is helping then I would run the truck with the radiator cap loose or only on the first position so that it will not let the system build pressure and the pepper will have a better chance of holding til you can repair it.

You can go to a radiator shop and they have a tool that can be placed on the radiator and it will pump up and pressure up the system to operating pressures and then you can check for leaks or cracks in the head casting.

Did you add a mixture of antifreeze and water when you found the radiator "bone dry"?

 

[DrkZide]

I bought five gallons of the premixed coolant. I've only used about 3 1/2 so far. The pepper helped a little in the morning and when I got back to my truck after work I added a good amount more and added more coolant (although I noticed a good amount of the coolant I added went to the overflow but aren't sure it's going back to the radiator). On the way home last night it was around 124* then all within a minute it spiked to 260*, I lost all heat, then it went back down to 150* and my heat came back. I checked the head again when I got back and there was no more "smoke/steam". So the pepper did something.

I've been running the cap fully closed. I notice that went I shut the motor down the excess pressure is vented off into the overflow but I'm not sure if it's sucking more coolant back in when it needs it.

 

[folkenheath]

Based only on what I saw in the picture I am going to say that the head is cracked in the water jacket and is leaking fortunatly to the outside.

I would have to agree, looks to me like a big crack, like the head was frozen or way over torqued.

 

[jnj]

When your temp goes up and down like that its because you have air in the system. Start the truck from cold with the radiater cap off then let it run until the thermostat opens. Usually about the time the thermostat opens you will burp out some air and a little coolent. Then you can add more coolent if needed.

 

[DrkZide]

I would have to agree, looks to me like a big crack, like the head was frozen or way over torqued.

The frozen part might be feasible. It was -17° last week (Windchill was -40° but I wouldn't suspect that to be an issue inside the engine compartment) and after that we've been around 0° +5° with highs around 25° that last like an hour lol

Would that be cold enough to crack a head? The leak seems to have stopped for now. I'll try and burp the air out of the system when I get home, since it did that weird spike and drop again this morning.

 

[folkenheath]

The frozen part might be feasible. It was -17° last week ...Would that be cold enough to crack a head?

Definitely if your antifreeze wasn't up to par. Depends on your mix and how old it is. The bad part is, usually blocks crack before heads do if the coolant freezes.

 

[DrkZide]

Definitely if your antifreeze wasn't up to par. Depends on your mix and how old it is. The bad part is, usually blocks crack before heads do if the coolant freezes.

There was not a lot in there and what was in there felt like a snow cone when I squeezed the lower radiator hose. I'm not sure when the PO changed the coolant but I'd say it's safe to say it was pretty old. Is there a dye I can put in the coolant to see if it's leaking from the head, block or where the head meets the block?

 

[bradshawtech]

There is a dye you can put in there to check for leaks and cracks but I am not sure where you could buy it though.

How confident are you that the thermostat is operating correctly? It sound to me like it could have failed you or is installed upside down. The spike in the temp is why I question its performance. It will not "burp" if it is not working correctly.

50/50 coolant is expensive, I hope it warms up soon for you so you can pull the motor apart if need be.

 

[DrkZide]

I would imagine it's been working since it was fine until the last freeze a few days ago. There's a 383 for sale on Craigs for $1000 if I need to swap the motor in a hurry and possibly rebuild this one if it turns out the heads are cracked. The leak on the side of the head seems to have stopped completely though but the coolant level is still erratic.

 

[bradshawtech]

Good luck.... That seems like a way too good price for a 383. Be careful to not get someone elses engine that might have issues.

The CK5 brotherhood is here to help. I am quite sure there is someone in your area that might have a line on a good used engine.