What causes so much pressure in my 1994 Ranger?

My 94 Ranger has over 300K miles on it, so I realize almost every part is probably on the verge of failure. I noticed a burnt antifreeze smell a couple of weeks ago, checked under the hood and could see where rusty antifreeze water had come out around the cap and spilled down the side of the radiator. I removed the cap and sure enough the spring had rusted past the point of being useable and the rubber gasket was severely warped. I replaced the cap and the next day after driving my truck to work and shutting it off I could hear a loud garbling noise in the Upper Large Radiator Hose (Sorry, I don't know part names). I just let it go a few more days and then noticed scalding water entering the reservoir through the little Diverter Tube. Today I guess the plastic reservoir had enough because there was a loud pop from that area on the way home. Does anyone know why this is happening? I'm thinking too much pressure maybe from a clogged heater core. I'm only guessing. I don't know if it is a relevant piece of information or not, but until all this started occurring my temp gauge stayed way over on cold even after driving more than an hour. I need to get this fixed ASAP so I appreciate any knowledgeable input. Please don't say replace the truck, that's not an option right now and these repairs are becoming a valuable learning experience. I'm going to go dig through my Haynes repair manual, just wanted some community input.



Thanks Very Much,



-LTWhat causes so much pressure in my 1994 Ranger?
Sounds like the cooling system needs a good flush. I don't use the stuff you purchase to clean at the auto stores as it causes other problems. Being you have so many miles on it, I'd use Dawn dishwashing soap like I did on my Blazer to get the muddy DexCon out of the system which was clogging everything up. Put about 1/3 cup in the radiator, place the cap on, start it up and let it get to operating temp. Let it circulate for about 20 minutes and then shut it down and let it cool so you can get the cap off without spewing all over. Disconnect the upper hose where the water is returned to the radiator and lay it to the side so it will pump the water out as you are filling the radiator with clean water from a garden hose. Keep the water running in it until it runs clear and the temp should be about normal. Stop the water, reconnect the upper hose and repeat the cleaning process again unitl it runs clean again. After the 2nd time, make sure you drain the radiator, hook up all the hoses and then put in 50/50 mixture of either Prestone AntiFreeze(the Green stuff, not the long life junk). That may help your overheating problem.
Make sure you have the heater running at high heat so it circulates through the hearter core! You will not get all the old stuff and soap out but a little of either won't matter!
You also may have a radiator that is bad and all clogged up. This cleaning style "MIGHT" help also!

Hope this helps.What causes so much pressure in my 1994 Ranger?
Yes try flushing the entire cooling system, if it is clogged that severely then the temp gauge may say it's cool when in fact the engine is close to failure from friction heat. Common problem because the temp gauge runs off of coolant temp not the actual engine block temp thus if the coolant is not flowing through the block to transfer heat then the coolant will not change in temperature although the engine is dangerously hot. This loud popping is most likely a slow trickle of coolant into the block where it then evaporates. The reason your overflow is filling could be that the clog is causing whatever coolant enters the block to evaporate and force the coolant back into the clog itself and pouring into the overflow. I would recommend taking it to a shop were they can pressure the system and force whatever blockage out of the system.