Topic: overheating 87 MJ 2.5... radiator reccomendation

[dasbulliwagen]

Ive been having occasional overheating issues with my MJ lately. The first time the relay for my elec fan stopped working and boiled it over. It puked out all the coolant. So I replaced the relay which got the fan working and refilled with new coolant. I didnt have any issue for quite a while but then out of the blue the dummy light came on telling me it was getting hot. The fan was working, It didnt fully boil over but it was bubbling into the overflow bottle. So I replaced the 195 thermostat I put in it several years ago with a new 180, new coolant again and new rad cap. First trip out I did a trip to the next town to help out a buddy with  no issues there or back. Then on a trip to the other side of town to get gas and on the way back the light started blinking at me again, so I turned the heat on full which helped some. This is making me thing the original looking radiator might not be doing all it is supposed to do. When I did the thermostat I flushed through the rad with a hose from the cap having it blow out open thermostat hole. It seemed to have good flow, but it looks pretty well corroded in there. And FYI the water pump isnt that old. It was a Chrysler reman bought from the dealer. Hoses were new at that time as well... been maybe 5-6 years ago. Ive never had air pocket issues in the past so Im not sure that is the issue. Does anyone have any reccomendations on a new radiator. Looking at google there is one called Genesis auto parts that lists an all aluminum single core for a good price $118.99. Seems better than the plastic tank ones. Or should I spring for a 2 core? Any opinions are greatly appreciated.

[Jeffy]

Can you look into the cores from the input end?  If they'res a lot of scale, that will reduce the flow of the radiator and insulate the passages so the coolant isn't as efficient.  Also check the fins on the radiator.  Are they corroded and flaking off?  How about the clutch fan?  IIRC, the electric fan is an AUX fan.  Does the clutch fan spin freely or does it stop after 1/4 turn?

If you get a new radiator get one for a 4.0L and get the AT version while you're are it.  For copper radiators, 2-core would be for the 2.5L and a 3-core would be for the 4.0L.  I think at that time they were still using the copper radiators.  The two companies that make OEM's are Crown and Omix-Ada.  Also keep in mind you have a closed loop system if it's stock.  You could use this opportunity to switch to the more reliable open loop system that the later MJ's and XJ's had.  The open loop system has a radiator cap on the radiator.  Don't mix up an open loop radiator with a closed loop if you're keeping the closed loop system.

In any case an aluminum radiator usually had one wide core.  Though some are made like copper radiators with smaller cores.  Wider cores are better since they allow for more flow.

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[dasbulliwagen]

The 2.5 and 4.0 radiators in the XJ MJ are different. The 2.8/2.5 radiator is square and the 4.0 is elongated. Im not sure its possible to mount a 4.0 rad in a 2.5 without changing the whole core support. Im just not willing to do that at this point. I have a Jeep WJ electric fan grafted to a 2.8 fan shroud so it bolts up like stock being controlled by an adjustable fan controller. The stock clutch fan is gone. It is pretty crusty inside. Im just weighing my options right now. I do have a couple spare stock rads from some 2.8 parts trucks (one XJ, One MJ) and theres a rad shop about a half hour away. Maybe Ill send my spare over there and see what it will cost to have an old one gone through.

[Jeffy]

Doh, my bad.  I would think that the Wj fan would be able to push enough air.  Do the stock radiators have plastic tanks?  Though for $100, I'd probably go ahead and replace it with whatever.  Most of those generic aluminum radiators use a generic core so they cut cost.  You might check ebay and see what they have as well.

[dasbulliwagen]

Stock original is a copper unit. Ive had the WJ fan on it for 5-6 years with no issues. I hope Im not having cyl head issues. I did a test at work for combustion gasses in the coolant and came up negative. And its still running fine, so it just makes me wonder.

[Jeffy]

The closed system has always been a problem for the XJ/MJ.  That's why they switched to the open system. 

[Mnkyboy]

The 2.5l MJs/XJs all came with an open system.


I put a 4.0l radiator in mine with dual electric fans.

[Mnkyboy]

[dasbulliwagen]

Replaced my radiator last night. I ordered what was advertised as a 2 core, but wheh I received it it was a single core, but double thickness, so I guess its all good. I installed it with new coolant again, a bottle of water wetter, and an 18lb rad cap for a TJ. I took it on a 1/2 hour (one way) trip and back today with 500 lbs or so of stuff in the back with no issues. Hopefully this fixes it for good. The old rad was in worse shape than I thought it was. Leaks had begun externally (but not bad enough yet to leak to the ground) and like was said, it was pretty crusty inside. Thanks for the help.

[dasbulliwagen]

1 Month update: Still running cool with no issues. Working on saving up for one of those aFe headers mentioned in the other thread. You guys are giving me tons of ideas for my upcoming rebuild of my spare engine. I already have a purple cam ready for it. Thanks again for all the help.