'88 Nissan Pickup overheating

[Dave H]

To update, the truck has been to the shop for the fan clutch, and the very next day it started overheating and when the wife pulled over, blew the upper radiator hose off the radiator. Back to the shop it went. Both radiator hoses have been replaced, and they replaced the thermostat (which had been replaced atleast once since it started running warm with no effect). I doubt the thermostat was it, but so far the truck isn't overheating anymore. I'm wondering if maybe the lower radiator hose could have been "collapsing", thus restricting flow?
Gary and H2,
Good points you guys are making with the radiator. I'm thinking of just replacing it anyways, as it is the original (18 years old). When the truck would get warm, the wife would turn the heater on, and the temp would drop to normal. So this would verify Gary's assertion that running the heater adds cooling capacity via the heater core. Maybe the truck was running right at the limit, and the added thermal load from the AC pushed it too far.
Anyways, after getting the overheating fixed, the very next day the clutch went out (pedal would travel to the floor). The slave cylinder gave up. So that has been replaced, too.
Hopefully this is all that will happen to it for awhile. Up until this point the truck has been very reliable. We'll have to see how it goes, but we were planning on this truck going to our daughter for her first vehicle in 2 years. Luckily it's the wife's truck, and is used primarily for short trips in town (less than 5 miles).

Thanks to everyone for their assistance.

Dave

 

[Gary Allan]

Well, a new rad is cheap if you do it yourself. Not so cheap at the shop level.

Your lower hose could surely have been collapsing ..assuming that it didn't have the coil that is traditionally inside most. This in itself shouldn't have altered the cooling just because of AC. That is, I think it should have caused problems all the time

Good luck!

 

[m2200b]

It's an 1988 mini truck. Not replacing the radiator or clutch slave until now is doing pretty good. If you haven't changed the heater hoses yet add them to your list of what is worn and fails in that time period.

Still a good choice to pass on - as parts are available including even the option of swapping a JDM motor or transmission.

 

[H2GURU]

Dave H,
Well Dave, the fact that your water pump is producing volume that your CLOGGED RADIATOR can't handle should be obvious now that the upper hose has been blown off. Gary Allan, if your done pumping out your basement, please chime in here!

 

[Gary Allan]

Well, that makes sense. You do have a pressure drop across the rad ..even a clean one. It would reason that a clogged rad would produce more back pressure.

What I can't quite figure is how the rad hose blew off and the cap didn't just vent the fluid. That is, the clamps ..and the pressure that should have been required to force the hose off, should have surely had coolant pumping out the overflow.

I guess with an event like this you wouldn't know if it was or it wasn't ..but you should be able to withstand system pressures of 30+ lbs without popping some hose off