Heat/Temp Problem

Folks,
I am having an issue with heat in my 87 W150. I have heat, but it is lukewarm at best and the much bigger issue here is that it seems to be losing fluid, not much , but enough to get the heat to the point where it wont blow hot. When I originally had this issue last week, i suspected the thermostat because the temp gauge would climb slowly to almost full, then drop quickly, indicating that the thermostat was finally opening. So, I changed it to a 195 and things looked good for a while, as I also topped off the radiator.
The next day, I still had lukewarm heat at best, so I flushed the heater core with a hose. Flow seemed to be ok as I was flushing it. Hooked it all back up and it was ok for a day. Not great heat, but better than before.

A few days later, I am back to no heat again. I looked at the overflow tank and it is full, so I wondered if the radiator cap could be bad, allowing flow out, but not for the return, so I replaced the cap.

So, here i sit with not heat because as soon as I put it on, the temp gauge goes up and the heater blows cold. Maybe the heater core is leaking? (cant see anything inside the truck and nothing under it either) or my fear is it is a head gasket, but the truck is running like a top.

Anyone have any thoughts on this one?
thanks
-Joe

Not sure about the newer rigs, but does yours have the heater control valve spliced into the heater hose like the older ones (70's)?
If so, did you check to make sure that the valve is actually opening/closing?
I say this because I've seen where the heater control valve, when it gets old and crusty, the cable will push/pull the arm back an forth, but isn't actually operating the valve itself.

Usually if you've got a bad head gasket which is causing it to run hot, it'll be hot all the time. A leak-down test will tell ya pretty quick though if it's a bad gasket/cracked head.

Joe,

I had a similar problem with my Jeep. It turned out to be the water pump. There is a tiny weep hole at the bottom of most pumps (SB Mopars included) which permits coolant leaking through a faulty seal to gradually drain out to the ground. Trouble is, when that leak is very slow and/or there is a lot of suspension in the way (such as on 4Xs), then little or none makes it to the ground. In such a case, it can be the very devil to locate.

Look for "green stuff" on your steering linkage/front driveline components. That will almost surely indicate a water pump leak. Confirm by getting under the truck with a flashlight after recent engine shut-down and looking up at the bottom of the water pump. Is it wet? Bingo!

Jeff

So last check you were not loosing fluid as the overflow tank was still full. Assuming that is true my best guess would be the heater control valve is sticking. Since you are not having overheating issues I don't see it being a head gasket.

You won't necessarily have an overheating issue with a bad head gasket. My head gasket is leaking antifreeze and I'm not getting any heat either--I just assume the bad gasket isn't letting any pressure build and therefore causing it to run cooler.

Hope it makes it to the spring!

After it's run awhile feel both heater hoses close to the firewall,should be about same temp.as top rad.hose(hot)If they're hot may be the heat control door in the box.

Could the vac lines for the climate control be damaged some how? Mine was damaged at the joining connector from the lines and the climate control.

It figures.... I had it pressure tested and sure as sh*t, its the head gasket. I cant seem to catch a break. I was really hoping that I would have until spring, but looks like I might be out in the cold once again changing heads.... Anyone got a good 318 lying around? :-) thanks for all the help and support....
-Joe

ok, After quickly contemplating poring in a bottle of Blue Devil Head gasket sealer, I came to my senses and decided to fix it right. Anyone care to voice their opinions as to what direction I should take with the repair? new heads, have the old heads sent out to be reconditioned? if so, new valves? any "Might as well's" that anyone can offer would also be appreciated.
thanks
-Joe

Original motor? How many miles on it? It would be a shame to spend money making the simple fix only to have more problems later. At the least I would go for a complete topside rebuild and have the heads done by a good shop. Also replace the timing chain and water pump too. BUt then again maybe a budget rebuild or a crate motor would be a better option. Depends on what you can afford and if it's a daily driver.

Just have the old heads rebuilt, shouldn't be nothing wrong w/ them. Just have the magnafluced to be sure they aren't cracked, they aren't very prone to so they should be okay. If so, have them resurfaced, 3-angle valve job, have the guides and valve springs checked out and replaced as necessary, new valve seals installed, and they'll be good for another 25 year Should cost around 200-300 bucks for the head job. Gaskets you'll need should be around 50-60 bucks. Wouldn't be a bad idea to change the oil and filter after everything is done either.

I would also put a new water pump on while you're at it, it could be bad w/o leaking. I've seen them w/ the fins rusted completely off, essentially killing all circulation. Could be the root of the whole problem. If the front seal looks to be leaking oil at all, might as well pull the balancer off and replace it also. Lot easier to do w/ everything tore down already.

If it's the original engine w/ over 100k on it, I would also have to agree w/ putting a new timing chain an gears in it. They have nylon teeth on the cam gear that get old and break. I just did a cam swap on the 130k+ mile '85 engine in my '72, and about half the teeth were broke. Chain was pretty stretched also. I'll see if I can find it and post pics sometime.

Well, thanks for all the info there folks, but I have to tell.... I poured it in..... After going back and forth, buying the gasket kit for the heads and being generally wishy washey about the whole thing, I finally decided a course of action. I poured Blue Devil in the truck. I learned that the motor had about 166,000 on it and given the fact that I have done a few "upper half" jobs before that resulted in only a few months until the bottoms give way, I figured this motor is out. And if I have decided that this motor is out, then I am replacing it with a 383. so, I poured it in and guess what. So far, so good. But it's only day 3. It did stop the coolant loss though. Hopefully I get thru the winter and in the spring I have a self built 383 ready to drop in. Now I just need a 383. Anyone got a project block/motor half done/ something they have no time for anymore?
again,
thanks for the info. Appreciated.
-Joe