This isn't really third gen related but I figure its running the same engine as my transam (305 TBI) so I would giver a try

I bought a 1989 GMC Sierra SL for $2000. Kicker was it was running good at the car dealership I bought it from. I went and got a 10 day on it and started driving it home when she started puffing white smoke. I know white smoke means head gasket failure however here is the deal...no coolant in the oil, no sweet smell from the white smoke, and no overheat. The exhaust however is wet and smells of gas.

Now I am at a loss as to where to begin looking. My buddy said it could be just the valve seals that are fried and its burning oil but that should be blue...but then again I am colour blind so I probably can't see the blue. I think he might be right about the burning of the oil because when I got home the pan was dry and the crankcase filter is getting some blow by.

I am not sure if the dealership will take it back and to be honest I really like this truck and sorta don't want to give it up but I have a feeling the dealership will just be like "sucker!!! bye now!".

Well anywho, if anyone has any ideas let me know. I would be very greatfull.

oh and sorry if I seem sorta out there or my sentences are stringed together, sorta panicking over here.

 

Step 1, take it back! If step 1 fails, come back and we'll have to invent a step 2.

 

ok so step 1 has failed. I explained to them what it was doing and asked them if it was too late to back out and they said "sorry the vehicle was as is as lies buyer beware". SO!!! I guess now that its confirmed that its mine that I might as well see if I can fix this thing.

I have been looking online at possible problems and one of the thigns that was mentioned as that the 305SBC heads were notrious for having valve seals fail which could cause this issue. Another thing that was mentioned was the headgasket could be going but once again, no smell of antifreeze out of the exhaust. Someone else mentioned that the head itself could be cracked or damaged. My buddy at work hopes for my sake that the rings aren't fried...however if thats the case then the cost to rebuild a 305 VS buying a used one is proably greater.

I am going to pull the heads off of it and see what condition they are in and while I am at it replace the gaskets. Any other advice?

 

I have run GM heads with no valve stem seals at all (some moron left them out, didn't even use the O rings) and the engine smoked a little at startup but not while running. I don't think there is enough valve to guide clearance to cause that much smoke just from bad seals.

 

You got a "10 day"
I took that to mean a 10 day test drive. Are you beyond that?

 

no the 10 day is a permit which allows you to drive a vehicle that has been transfered over that is un-plated. Basically gives you 10 days to get the vehicle inspected and certified. The ownership however is still in the dealerships name.

 

I doub't it's coolant. My guess is it's running rich, and the cat is working it's tail off. Could be a stuck injector, could be a clogged fuel filter, or a bad 02 sensor.

It doesn't sound like a huge deal either way. You really need to check the normal stuff, plugs, ignition, etc. Scan it, see how it's operating.

It's still not a bad deal for the truck. Assuming it's a 4x4. If it's a 2 wheel drive you got raped.

If you have other questions, let me know. I have had a bunch of those trucks, including newer ones with vortec engines, as well as some older (pre 88) with sfa.

-- Joe

 

I have a catt'ed 305 that is running way too rich (CC Qjet is taking a dump) and it blows BLACK really bad when you step on it even a little. I don't know about white being rich?

 

The converter converts it to water, which burns as steam. If your seeing black, your converter isnt working, or your soooo rich it still isn't working

-- Joe

 

Interesting. Mine must be really really rich then! The carb has had the IAB tampered with and I haven't had the time to reset the MCS dwell. The cat is brand new, less than 500 miles on it. Woopsie!

 

Well I know its not coolant. I took it out for a quick spin (30 minute cruise) last night and checked the coolant when I got home (after it cooled down of course) and the rad was still full/overflow was showing the proper readout. That whole idea of the engine running rich sounds about right though because the exhaust is really wet and stinks of unburnt gas. Maybe when I get home I will take out my datalogger/dirty old laptop and plug it into the ALDL port and see what it says. There is no SES light coming on though and the bulb does work. Well I will see what pops up and report back after. Thanks or all the advice.