I have a 97 with a 3.8 L with high mileage. I have an engine overheating mystery where the water in the radiator isn't getting pumped into the block. The block boils over in a matter of minutes, while the radiator water remains stone cold. I suspect the car won't get far if I drive it. Here's what I've done: Replace waterpump, thermostat, and tensioner pully (which is part of the cooling system with heater hose routings built into the frame of the tensioner). After replacing all of these, it still has the exact same problem. ONE THING THOUGH...when the temp got up to about 230, I turned the engine off, then back on, and it pumped just enough water from the radiator into the block to pass over the dashboard coolant temperature sensor to make it go from 230 degrees to 185 degrees in 15 SECONDS. Then, within a minute, it was up to 230 degrees again. This problem happened all of a sudden where it ran at normal temperatures for years, then overheated all of a sudden and the problem continues every time I start the engine and let it idle. Anyone have a "no doubt about it" idea of what's going wrong? If not, any educated guesses?

 

How you flushed your coolant system in a while? Sounds like maybe some blockage. I guessing you physically touched the radiator to tell it was cold. So you might try flushing the system. Otherwise you might try replacing the coolant sensor sending unit.

 

I haven't flushed in a while. Something has to be blocking or mechanically impeding the water from moving from the radiator into the block. There is nothing wrong with the temp sending unit since it's plain as day that the water is boiling in the block and steam backflowing into the radiator and out the open cap. I'm going to go flush it right now, but if anyone else has anymore ideas, please speak up.

 

I just finished the flush. It didn't do any good, same problems. HOWEVER...I theorized that it could only be air in the cylinder jackets causing the boil over. So, I repeatedly let the car heat up, turn it off, take the radiator cap off, start the car with the cap off, then add water. Somehow it seems to be slowly getting the air out and it almost is working normal. Still overheating a little when I stop and let it idle, but it doesn't boil in the block and almost explode like it did before. I'm 90% sure it was air in the top of the block.

 

IMO, you need a new radiator.

 

It didn't need flushing, didn't need a new radiator, but thanks for all of the "stab in the dark" suggestions. Write this one down in your book, it was air trapped in the top of the cooling jackets in the engine block. Plain and simple, no doubt about it, I'd stake my life on it. This condition caused boiling to occur at the waterline in the top of the block while the rest of the block only got up to 180 degrees. By the time the thermostat opened at 180, there was pressurized steam in the top of the block that had no place to go but out of the radiator cap, forcing coolant out ahead of it. This made the air pocket condition persistent, or even worse. Immediately after I got the air out of the block, I loaded my luggage into the car and drove it 700 miles to Florida without a single problem. The temperature never ever got to the half way point between 160 and 210 degrees (the 10 o'clock position), which means, according to the dashboard indicator, it never got to the 185 degree mark.

 

Good to hear you fixed it, before it got any worse.

 

good deal. sorry no one could help you, im not too good with troubleshooting the 4th gens, im a 3rd gen guy myself