Some thermostats have a small hole or crimped "V" vent on the edge to equalize pressure and prevent an "air bubble" from trying to impact the stat operation. But since there are no check valves or complex pumps, pressure is pretty spread out. I think it is considered "good" that it will hold pressure after it has cooled off. Some have used the small filler port on the top of the radiator to mount a gauge for pressure testing. Obviously, a head gasket leak can add a lot of pressure and that upper hose can become rock hard. If coolant is being lost, it has to go somewhere (on the ground - put down fresh cardboard), or out the tail pipe, or into the oil (milky). From my short time of slavery to this rolling tea kettle, and hours of research on line, I would say that overheating, leading to early HG failure, is one of the top complaints.

 

alrighty gentlemen i got a couple more questions before i go and pull the trigger on a new head gasket job.

upon removing my radiator from my truck for inspection, i found a fairly large amount of debris between the radiator and and ac compressor im guessing(smaller radiator). im talking alot of leaves and other yard waste. it looks as if this truck sat for a long time before i got to it. was wondering if something simple like that could be my issue, and secondly i was using compressed air to remove all this garbage when one section of the fins that was already a pinkish color turned to dust upon being hit with air. theres a 3' x 5' section on one side that pretty much evaporated. then with hose clamps and old hoses i sealed off the radiator and where the upper radiator hose fits i hooked up my compressor and it held pressure. so with those fins falling to pieces does that show a leak in the past? or something that may be relevant now?

now after the last time i ran the truck before i dismantled the whole coolant system, i felt around on all the hoses and radiator and everything felt uniform and fine, im ready to rule out blockage.

would a bad thermostatic sensor and or sender unti be the culprit?
maybe a faulty raditor cap?

or am i holding on to tightly and just need to go with the HG option, keep in mind besides the overheating and large amount of pressure i have yet to find any signs of a HG leak.

this is the last time ill ask you guys before i start ordering some real parts.

thanks in advance, you guys on here are the reason i havent taken this sweet little truck back yet,

brad

 

Clean up all that debris and put the rad back in. That WILL cause a lot of overheating issues.

 

If it works after cleaning it up, start saving for a new radiator.

 

Gunk between radiator and condenser will show up when running, but usually more noticed when going slow, stop and go, or parked and idling. If you have gunk there, you may also have it inside the AC fan under the dash. Three bolts and it drops down, won't cause overheating but makes AC wimpy. There is a tech post about how to fab your own pollen/leaf filter for under the hood. You might save some $ by having radiator flushed and rodded out, it cost me about $65 at an indy shop, included some soldering up of weak spots. Disco 1 radiators are brass and copper and take repairs well. Salavage yards around here get $49 for a radiator you pull.

When engine is cool give that fan a spin - should not turn more that 1/2 rotation. When warm and OFF, give it a spin - should turn more, but should not "free wheel". Fan will impact cooling at low speeds and idle, not when your are at 45 mph. If radiator is old enough to have problems, so is the fan.