Hi everyone, I have a 96' 351W out of a bronco that I have put in a rockcrawler. She was being worked very hard one weekend and the exhaust manifolds were glowing red in the dark, the engine reached 230 deg. the radiator cap released water for mabye 20 sec, I shut the engine off and temp rose to 250 deg where I turned it back on and let it idle till the temp returned to normal. Next day the water in radiator looked fine, second day there was what looked to be oil in coolent. The engine has been running poorly at idle prior to this whole incedent, Vacume gage bouncing inconsistantly between 15 and 17 (so this could be unrelated to the overheating incident). Compression test shows all cylinders to be 165 except number 3 cylinder reading 160. Its hard to tell if there is water in the oil, mabye a slight bit, like I said very hard to tell. Also, when you let the engine idle with the radiator cap off, the brownish coolent bubbles over and out of the radiator. When this brown stuff dries it looks like a yellow powder. So im just looking for opinions on what might be happening here, obviously things point to head gasket but the compression test doesnt make me believe this, is there anything else that I could be overlooking before I tear the top end of this engine apart? Thank you for your thoughts as I do not have a ton of experiance diagnosing a blown headgasket/brown coolent.

 

let it run a full temp cycle and shut it off. Pull the oil-fill cap and look at the bottom of it.If there is a thick film almost the consistancy of peanut butter, you have a blown headgasket/warped head.

 

Lemme tell you a little story about blown head gaskets, bent rods, and burnt coolant.

Once upon a time I bought a green '94 Bronco that had been garage kept most of its life. The day I got it, I flushed out the brown, rusty, burnt coolant and put fresh green stuff in. Next day the water pump started leaking. Keep in mind, I'd drove the truck around town for a couple days before I brought it home. The following bright, warm Sunday morning, I go to replace the water pump. Break off one of the studs in the block. Timing cover seized to engine block. Fast forward three weeks, engine is out of the truck on a stand, and I get the oil pan off. Found chunks of aluminum of mysterious origin in the pan. After more inspectifying, found #4 piston had the skirt knocked off, and found aluminum chips still on the crank throw. Still not knowing what and where these mysteries wre coming from, I call in the big guns and get some buddies over to examine it. We found the #4 rod had a slight "S" bend in it, and when we pulled the heads, the head gasket around the #4 cylinder (seeing a pattern yet?) was burned away and the corner of the head gasket had rotted off. It was around that time when we noticed the burnt coolant trail down the side of the block.

Moral of the story: pull the heads and check everything. Make sure all the pistons are coming up to the same height. Compression tests can't determine blown head gaskets. You have to test the cooling system. But if you're seeing oil in the coolant, you don't need to be testing anymore. It's past that. Bandaids aren't going to fix it, that motor's hurt.

 

Blown headgasket.

 

I second the notion

 

Well, I think you guys are absolutly right. I just go ahead and pull the thing apart. What are the chances of damaging a block like this from overheating, should I even be woried about the block at all?

 

I wouldn't be too worried, however I would check the head mating surface for warpage, it's rare on a cast block but not unheard of.

 

X 2 Its allways a good idea to have the heads checked , you should fine somthing when you look at the gaskets , get a good set a head gaskets like felpro....Lew

 

You'd have to get it pretty hot to damage the block. Heads however, even if they're iron heads, they can still warp. I can also guess that you probably got some oil cooked to the rods and maybe the crank as well.

 

Well i pulled the heads off and there is the penut butter stuff packed in both rear water jackets in both heads. Surprisingly, the head gaskets looked fine! so now im nervous, does this point to a cracked head perhaps? Or the block, though you guys are saying a damaged block is pretty unlikly. Might be a good time to get some GT40's or somethin if the machine work to check heads are expensive.

 

Take a really close look at the mating surface of the heads and the bock, is there any really shiny areas between water/oil jackets? I have had blown head gaskets and the gasket looked fine upon inspection but one I looked closer at the components I could see where the gasket failed. It is possible however that you cracked or warped a head. I would take them to a quality machine shop and have them checked and resurfaced if needed.

 

Ok, ill take a real close look tommoro at those gaskets and go ahead and just take these heads to the machine shop! Thanks for all the help everyone, i really appreciate it!

 

Start posting pictures...alot of trained eyes around here that can spot things that others might miss.

 

really? I discovered that's what caused my 351w to bite the dust, water pump failure that cooked the oil. Let this be a lesson to everyone, a stock 351w is not meant to pull a D-8 dozer everyday.

 

P.S. the temp gauge said everything was fine, I checked the sender and the gauge and both checked out ok.