Was driving early last weekend on a very cold morning about 8 miles and steam starts coming out from under the hood. Temp gauge is high but not in the red, CEL pops on and I got no heat. I drive 1/4 mile to NAPA and let it sit 30 minutes to cool off. Radiator and hose cool off and I pop the cap and antifreeze is not visible......I buy a gallon of 50/50 green and it takes about 1/3. No leaks out of radiator anywhere. It starts right up and I start to drive home. It's running fine and temp gauge is normal...so I decide to drive on another 10 miles to ski the day as planned.

I come back 6 hours later and check the antifreeze and it's about an inch low, so I fill it up and drive home no problems, except CEL comes back on when engine is warmed up. Once home with a light I can see a very slow antifreeze leak dripping on the skid plate coming from the water pump area only when engine is running.

So I have muti concerns:
1 - So I obviously over pressured the water pump....should I assume the Head Gasket is blown also??
2- Could the engine coolant temp sensor be bad, thus the CEL and it's running much hotter than the temp gauge reads? The radiator and hose seems warm as usual but not crazy hot.
3 -Can I just keep checking the antifreeze and running it....knowing the water pump could let go...but it's holding it's on for now.
4 - I'll probably drive 40 miles to Reno to have the water pump/timing belt/coolant temp sensor replaced while I'm away for the holidays.......what if I don't do the head gasket at that time?
5 - What's an average shop charge for head gasket replacement run? Anything else to consider replacing while I'm in it? thermostat?? Thanks in advance! barryj01@msn.com

Bubba,

I have the exact same truck. It is not what you think it is. I went through this this summer. Your head gasket isn't blown, YET! Unless of course you have coolant in the oil and white smoke out the tail pipe.

There is a coolant pipe that runs down the v-channel from the back of the water pump out to the back of the engine and up. It cannot be seen without the plenum and the manifold off. There's an o-ring that seals the joint between the water pump housing and the pipe. It goes bad and causes coolant to leak into the v. From there, the coolant burns off and will never be seen as a drip, a leak, a waterfall... Nothing. Completely hidden. I was going to take my truck across the country until i found this out, from a confirmed positive for combustion fumes block test. (That's when I hopped in my 87 4 banger and drive that! But that's besides the point)

So the coolant just keeps disappearing. You'll drive on the highway fine and then you'll get off or slow down, or come to a stop and it'll rise. You'll see there's no more coolant, and then you add more. And the cycle keeps repeating.

Don't drive it anymore if you want to keep it alive. Have the head gaskets replaced, the o ring for the pipe replaced, and the water pump and timin belt changed. I did it for 600 bucks this summer and the truck has never run better. Cool as a cucumber. I'd be happy to pm you pics. Just let me know.