2002 grand Cherokee overland, 4.7 H.O. v8. Sometimes after driving when I turn the vehicle off the radiator leaks, driver side on the bottom. It may do this once out of 5 or 6 trips in a day. It may not leak at all for a month then leak several days in a row. Does not leak a huge amount but enough to worry me. Leak appears to be at tank and core junction. Just wondering why it only leaks some times and not all the time?

 

It probably has to do with pressure in the system, when the pressure is high, it will leak.

There is a neoprene seal where the tank is mounted on the core and the aluminum is pinched to hold it on. You may be able to redo this pinch and cure your problem, but it requires removing the radiator. Years ago, one of the cures for a leak like this was to put a lower pressure cap on it or run with the cap loose. Today's engines run at about 210* so you have to have pressure to avoid boiling and overheating. Also, the engine management systems are designed to run properly at the normal operating temp of 195* to 210*. Anything lower will cause a rich fuel trim.

You might try a 7 or 8 psi cap and see what happens. Watch out about overheating that 4.7. They don't like it at all.

 

The 4.7 uses a 21lbs cap. Dropping to a 7lbs cap may stop the leak but won't do the boiling point any good. I would guess there is a crack in the plastic tank that spreads when there is pressure in the system. My step son's Dakota had that problem, I drew the short straw and had to replace it. A total PITA on a Dakota.

 

Yes, unfortunately, I agree with Bustedback. I just didn't want to give you the worst-case-scenario.

I wasn't aware they used a 21 pound cap. I think mine on the 4.0 is only 18 psi but I'm not sure. I don't think I ever looked at it close enough.

The idea of running that kind of pressure with plastic tanks gives me the *******.

 

Yep, it's a 21 pound cap. Looks like I will just put a new radiator in it. Looks like a royal pain in the but. My old hot rods and the XJ and TJ were no problem but this might suck. I hate plastic tanks.

 

Yeah, I agree with you. It is a PITA! Also, nobody on this forum has found a supplier for a Jeep radiator with metal tanks.

 

Metal tanks are not available.

 

Yes Busted, I'm aware of that. GM, with the Corvettes and Cadillacs, had the first all metal aluminum radiators and they had lots of problems with them. I remember putting sealer pellets in a Cadillac to get it to stop leaking. This was a GM factory fix. As soon as they went to plastic tanks, the problems stopped.

The problem is having a custom built all brass radiator made is way too expensive, even if the talent is still out there. I've seen them made for hot-rods, but not often. We just basically have to go with whatever the industry supplies.

 

Well got the new radiator in today. As I thought it was a pain. One of my hydraulic fan hoses is shot so as soon as I get one I will be done. Worst part for me was putting the lower hose clamp on the thermostat housing, no joke it kicked my butt.lol Did not have to remove front fascia.

 

It's like they built the vehicle around the radiator. Why do the engineers feel the need to make something with a life expectancy of eight years so damn difficult to get to?

 

Because like my Dad used to say, "They don't want you working on your own vehicle! That's why they have service departments."

 

I worked in a few service departments. We cussed a lot engineers every day...idiots.

 

I bet you did,lol