Driving with blown head gasket?

[Leadfoot]

Story:
Noangel's (Michelle) picked up an 88 K5. Previous owners wife overheated it (fan clutch wore out) and it blew the radiator hose (shut it down). Put new hose and clutch fan in and sold it to us. It idles a little rough, and I'm thinking it's a bad head gasket (or hate to say it, cracked head) due to overheating (P.O. said it ran perfect before the overheating and idles smooth as glass). A buddy of mine (mechanic) says it MAY also be an intake gasket warped from the heat sucking in air (if external leak you can find it by spraying carb clean, but if its internal it's tougher). I was wondering if I could drive this thing for a couple days to see if there are bubbles in the rad. or coolant gets low indicating head gasket or cracked head. I don't want to pull the heads if I don't have to, especially if it is just an intake gasket. My fear is if it is a head gasket or head, that the burnt antifreeze will F-up the converter. Anyone have suggestions or know if it will affect the converter or O2 sensor?

 

[BorregoK5]

Pull the plugs and do a compression test. Write each figure down and cross compare to each other and it might shed some light for you with minimal work.

 

[Leadfoot]

Funny you should mention that. I was talking with Andy (my mechanic buddy) and he said he would bring his compression tester over tonight and check it out. I'm assuming that's what he meant, but thanks anyway, that is good info/test to know.

 

[Blazer_Boy]

Drop some stop leak in that SOB and ride on! /forums/images/icons/smirk.gif I would think your torque convertor would be fine because it wasn't exactly driven constantly like that.

 

[Leadfoot]

I was more worried about the catalytic converter and not the torque converter, or is that what you meant /forums/images/icons/confused.gif ?

 

[Blazer_Boy]

Whoops, I just saw the word convertor. Catalytic convertors are the last thing on my mind, lol. We don't have testing up here and I think only one of our vehicles has a convertor. We have 2 Blazers, 3 Shortboxes, and a '90 Cadillac. Betcha can't tell which one is the daily driver with the cat convertor on it still. Man, we got a lot of Chevy's. Mom and I are trying to find a C3 Corvette too, lol /forums/images/icons/smirk.gif

 

[Leadfoot]

Yeah. Well driving is going to be minimal (read: non-existent) until I can do the head gasket. I did a compression test (with plugs removed and coil wire grounded) and the back three cylinders on drivers side were 105 or below (should be in the neighborhood of 150). The passenger's side were 145-160. There was even a spray of anti-freeze coming out of cylinder 3 while turning the motor over for the compression tests. I am going to replace both head gaskets along with new water pump and valve seals.

 

[Blazer_Boy]

Before you get in too deep, drain the oil. If you get a bunch of green comming out, then oil. Well, thats the end of that game. If its a nasty looking tan, than you still might have a chance. I'd be afraid of that anti-freeze leaking past the rings, into the crankcase, and ruining your bearings. When you get the heads done, be sure to get them plained. They could be warped and that'll straighten right back out. Good Luck (I've been there).

 

[NoAngel]

*Noangel going nucking futs wanting to drive her Blazer sooo bad!*
*Noangel saying a prayer that it's not worse than we think.* /forums/images/icons/frown.gif
BTW,thanks for all of your help!

 

[Leadfoot]

Changed the oil this weekend (I know I will have to change it again when I'm done with the new head gasket, but I figured it couldn't hurt and I could see the condition of the oil). No visable green in the oil (real dark though), and no oil visible in the antifreeze. Compression on the passenger's side was perfect and the driver's side was low on the back 3. Considering it was "supposedly shut down" fairly early, and that the heads are cast (not aluminum), I am hoping they will be alright. I am going to have the machine shop magnaflux the heads, and if they check out, plain them, check the seats and guides (lap if necessary) and replace the valve stem seals. It won't be cheap, but now is the time to do it and she is going to keep this baby, so it's cheaper now than in the long run.