Probably bad news. Is there any way a plenum gasket could leak coolant? I took radiator cap off and let truck warm up and there were no bubbles in coolant. I'm going to do a compression check next. Should I also do a coolant pressurization test? Are head/gasket failures common in these trucks? I just got truck so I don't know of any past overheating. It comes up to temp and stays in the operating range. Any wisdom is much appreciated.

 

If you had a blown head gasket you would have coolant in your oil. Check the oil and see if its a milky messed up color. I haven't heard of these trucks having a tendency to blow a head gasket. You wont see bubbles in the radiator unless you are burping the system.

 

^not necessarily.

a little steam and water drip out the muffler from a cold engine is normal. have you got continuous steam or white smoke out the exhaust. if so, and if you're losing coolant, then its either a cracked head or leaking head gasket, or maybe a leaking intake manifold gasket.

its not a leaking plenum. thats down low at the bottom of the intake, away from the coolant passages.

a compression check or leakdown test would be a good move.
also check your sparkplugs for 1 or 2 that look different from the others.

head gasket failures are not real common.
cracked heads occur far too often due to weak/thin stock castings.

 

compression test results:

Cyl#/psi
1 120
3 60
5 90
7 130

2 120
4 116
6 131
8 120

Forgot to secure TB in open position, not sure if that contributes to results or not.
All plugs looked same. Wet tested number 3 and it shot up to 135. All sound a little low. Will check manual for specs. 3/5 seem like gasket/head failure. Also, I put a lot of Stabil in fuel other day because truck had been sitting for three years. Didn't realize gas was almost on E. I wonder if that contributes to smoke in exhaust?

 

Well a lot of steam coming from the exhaust is a head gasket. I would be more concerned with cylinders 3 and 5. Since they returned to 135psi after wet test that means the piston rings are gone if I'm not mistaken.

 

if its smoking white you probably had some water in the gas specialy if it was sitting for 3 years.

 

sitting for 3 years - damn.
let it run awhile and make sure all the old gas is run out.
maybe put in some fuel treatment that treats for water. i don't think stabil does that, its more of a preservative....

monitor for oil loss and/or coolant loss.
compression might get better after the cylinders get de-rusted.

 

Yeah, I'm an idiot. Forgot to add the sitting for three year thing. I got a coolant pressurization guage. Hooked up, let idle to operating temp. I'm going to let it sit for a while, but if there is no immediate drop in pressure I assume at least coolant isn't getting in cylinders. Am I right in thinking this way....I must admit I am not a mechanic but more of a tinkerer with some mechanic skills.

 

Well, since you said it first. Sta-Bil is to be put in the gas before the vehicle goes into storage, not after. It helps keep the gas from getting stale and turning into varnish inside the fuel system.