95 JGC w/5.2 overheating. I have installed new radiator, cap, fan clutch, 180 degree thermostat, hoses and remanufactured water pump. I did break my fan shroud and will pick one up tomorrow. It runs fine at speed but will slowly climb when idling. At about 225 (I guess I'm reading the guage correctly) the cap starts hissing and the water in the coolant resevoir will start boiling out. I don't know what else to do. You guys have any ideas? :confused:

well I had a very bad overheating problem last summer, and replacing the radiator (NEW, from Radiator Express) did the trick. I end up killing the engine and the radiator within a month. well back then my tempature was constantly between 210 - 235, but I never heard hissing from the CAP. you might want to getting another NEW cap.

was the radiator brand new or used.

well I had a very bad overheating problem last summer, and replacing the radiator (NEW, from Radiator Express) did the trick. I end up killing the engine and the radiator within a month. well back then my tempature was constantly between 210 - 235, but I never heard hissing from the CAP. you might want to getting another NEW cap.

was the radiator brand new or used.
It was a new radiator. I admit to being not all that knowledgeable about radiators until I replaced this one and still had this problem then I started to read about two row and three row radiators. The new one I bought is a two row I'm sure ($180.00). I don't understand why if they come stock with a two row why you would have to upgrade to a three row. But I agree that I probably need to start with another new cap. The one I have now is a CST brand (never heard of that one before) but I'll try to get a Stant or something tomorrow.

you shouldn't have to worry about upgrading to a 3-Row radiator, the 2-Row should be fine. Start with a new cap, if the cap isn't holding pressure then the cooling system will not work properly. try to get the highest PSI that you can find (that will work) remember for every 1 PSI thats 3 degrees cooler you tempature will be, my 94 ZJ (5.2L) has an 18 PSI cap on it. If the cap doesn't do anything, replace the T-Stat with a 195 (OEM) Thermostat. My reason for this - the engine might be too hott for the 180 T-Stat and holding the T-Stat open all the time circulating the coolant through the system without allowing it to stop in the radiator and cool down. START WITH A NEW CAP (18 PSI) sounds like thats the problem.

Yeah-I just checked the one I have and it's a 18 lb cap but I've never heard of that brand name before (CST?). I'll pick one up in the morning.

Do you have any shroud on at all or just part of one? Running without a shroud will cause the temp to rise esp when at Idle. Also make sure you have all the air out of the cooling system this will cause the temp to rise.

OK- I put the new fan shroud on and also found (I hate to admit this) that when I replaced the radiator I put the fan blades on backwards. Corrected that and started it up and let it idle for about twenty minutes with the outside temp @ 83 degrees. Twenty minutes is way longer than it's been able to idle before. The temp guage slowly crept to 210 and seemed to be holding so I turned the air on. The temp guage slowly rose to the first small increment past 210 and then I saw water spraying on the windshield. Opened the hood and the part of the coolant resevoir bottle where the sensor is was spraying water out (water was boiling in the coolant resevoir). I guess I need a new bottle. So the problem is not solved but it is a LOT better. I still don't know why the coolant would be boiling in the coolant resevoir bottle when the temp guage was only on the first increment past the 210 mark. That's a long ways from being in the red.

By the way, am I the only idiot who can't figure out how to read the temp guage?

you did put a new cap on, right?

the 1st mark after the 210 is around 217 +/-. < that is still really high tho....

Replace the cap if you have not done soo yet. Make sure it's at least rated at 18 PSI.

Yeah I got busy today trying to get the fan shroud and forgot about the cap. Gonna try a NAPA 18 lb one tomorrow.