I have a 1985 F-350 w/ the 6.9 diesel. I was driving down the road and the radiator cap blew off and it blew coolant all over the place. I was wanting to know how can I tell the difference between a blown head gasket or a cavatated block. I've never heard of the 6.9 cavatating but I was told it was a common problem. I am also wanting to know how much I can plan on spending to fix this. It is a good truck but I only paid 3500 for it so it may not be worth it. I appreciate the help.
Jeremy

 

You are probably going to have no choice but to pull the heads and look. I don't think there is any other way to find the answer.

 

What do you mean the radiator cap "blew off" they have locking screw mechanisims (sp).

Radiator/engine coolant all over the motor compartment is not a normal indication of a blown head gasket. Do you have alot of it coming out the exhaust?(much better indication)

as The Diesel Dude pointed out...if it is a head gasket, or if it is as a result of degredation of the block. Really the only way to know would be to pull the heads.

I think you should find out if you just had a coolant leak from somewhere (radiator cap) before you do any dissassembly....

 

I would suspect it had overheated for some reason. If it had presure to blow the cap off maybe its just as simple as a thermostat. Just my thought. Its the cheapest thing to try first. Don't forget to check the oil for antifreeze and the exhaust for excessive mosture. those could be signs of a blow gasket.

 

It started running warm and the oil pressure was fluxuating(sp.) It sprayed a mixture of oil and coolant everywhere. Sorry if I wasn't clear enough the first time. Thanks for the help.

 

I replaced the heads on an in-law's truck which had blown head gaskets AND cracked heads. As stated above, it looks like you will have to pull the heads to see what is really going on.

Les

 

Hey Jeremy, Rick from Canada here. You forgot to mention it was the resevoir cap and not the rad cap that blew. Doesn't sound like your getting the answer your looking for. When my gasket went I had no oil problems whatsoever, just antifreeze spilling out. What you should do is put the heads back on with new gaskets, don't fix anything else. Gaskets will cost $100 or a complete head kit for $150(gasket kit). Put it back together and see how it runs. The 6.9 ISN'T known for cavitaion problems, especially under 200k (mine had 250K with a first generation ats turbo probably mid eightys, my other truck has around 300k and no problems, and thats without the antifreeze additive). Worst case senario you blew $150 to find out the block is cavitated. If anyone else on the forum disagrees, let him know. When you took the gaskets off you wont notice anything wrong with them. Its not like you will blow a big chunk of gasket out(which is very noticable). Mine was shiney, and that was it. The cylinders under the bad head were dirty, but the carbon just wiped off, must be the steam cleaning it was getting (HA HA). One other way to tell is if the injectors had gunky rust bubbles on them just below hte threads. Thats the coolant getting on them and baking. Hope this helps you more. If you have any other questions, please dont hesitate to email me.

Rick