96 rodeo cooling problems

howdy from saipan,
anyway my V6 rodeo keeps boiling over and/or runs hot. there is no coolant leaking at all and i flushed the radiator and removed the thermostat. the coolant was nice and green when i drained the radiator and it flushed nicely. it looks as though there is coolant flow when i take off the cap. does this water pump have a weep hole that indicates a failure? as i said, no leakage. i was thinking that maybe the flow i saw was just hot water expanding and displacing cooler water??
seems like a ghost in the machine. all mechancs out here are criminals, so i'd like to fix 'er myself. any thoughts? any tips on pulling off that water pump?...it looks tricky.

cheers

I had this problem with my '96 Passport - it would run cool most of the time, but then if I went up a hill, or ran on the highway it would overheat. If yours does this then the problem is capacity - that means your radiator is clogged, probably by hard deposits that can't be flushed. I tried flushing mine in both directions with heavy duty flush and it didn't do a thing. I replaced the water pump, thermostat, fan clutch, and all hoses. Still overheated. Then I replaced the radiator, and that solved the problem. At least now everything is new...

Hope this helps.

thanks, i will have another go at a flush and see if the capacity seems wrong.

it can be difficult to get all of the air out of the system

You may not see any difference in actual capacity of the radiator - it is possible for deposits to be present on the insides of the tubes that reduce the heat transfer (normal corrosion deposits can occur in only a few years from aluminum reacting with antifreeze). So you can have a radiator that 'holds' the same amount of liquid, but its heat transfer rate is very slow. What you get then is adequate cooling at low demand (puttering around town) and overheating when the demand exceeds the heat transfer abilities of the system.

When does yours overheat? If it overheats just from idling in your driveway, then you have a water pump issue, or a thermostat stuck closed, or even a nasty air bubble somewhere. But if it overheats only when the motor is working hard, then you have low heat transfer in the radiator.

thanks for the insight. is there a way to pressure test the radiator? or method to feel around for hot or cool spots? my next step will be to flush it with a chemical de-scaler, i reckon i may even have to take it to a shop and have them evaluate it. i noticed that the water pump can only be removed after ripping the front of the engine off and removing the timing belt (3.2L V6). are you kidding me?
......i'd love to find out that it is only my radiator................

oh yeah....regarding the trapped air bubble theory.....any ideas how to remove it if that is the case?

I personally have never had any trouble with trapped air in the Passport 3.2. I make sure I park with the nose uphill slightly, set the dash heat control to full hot, and then run the motor with the rad cap off until it starts to steam a little and I see some motion in the coolant inside the radiator. Then I cap it and let if come up to full operating temp before I top off the expansion tank. Check it after a couple of hot-cool cylces, but my experience is the 3.2 system is good at clearing air out.

I replaced my water pump when I did the timing belt at 130,000 and it looked like new. I doubt it's the culprit. These aluminun rads react poorly with ethylene glycol if you leave it in for more than a couple years (!)and create deposits that cannot be removed with conventional flushes - I doubt they can even be rodded-out, because the deposits are essentially like a thin coating on the metal preventing heat transfer, not an actual blockage.

I personally have never had any trouble with trapped air in the Passport 3.2. I make sure I park with the nose uphill slightly, set the dash heat control to full hot, and then run the motor with the rad cap off until it starts to steam a little and I see some motion in the coolant inside the radiator. Then I cap it and let if come up to full operating temp before I top off the expansion tank. Check it after a couple of hot-cool cylces, but my experience is the 3.2 system is good at clearing air out.

I replaced my water pump when I did the timing belt at 130,000 and it looked like new. I doubt it's the culprit. These aluminun rads react poorly with ethylene glycol if you leave it in for more than a couple years(!) and it creates deposits that cannot be removed with conventional flushes - I doubt they can even be rodded-out, because the deposits are essentially like a thin coating on the metal preventing heat transfer, not an actual blockage. The replacement rad I got from Advance Auto was $200 and it solved the problem immediately.

thanks daveox...you're a legend.

i pulled the radiator last night and filled it with CLR and let it sit overnight to get the grief out at the advice of a mechanic....i'll let you know if that worked.

Did the CLR fix the problem? I have similar issues and if it works for you it might work for me.

the clr got out lots of fine deposits. i assume that somewhere along the line a previous owner ran tap water. it really did cool better, but then the weep hole on my water pump finally let loose, so i had to replace that, (and the timing belt since i was already in there). i am gonna soak the radiator in clr for another day and get more stuff out later this week. it runs at a medium temperature, but it still "smells" too hot. i think the clr soak is a good idea if you think your radiator isn't leaking, but isn't cooling. i'll let you know if i exorcise this ghost...............