Turbo X_J

"anti-suction kink spring"
It's not a positive displacement pump so you would be hard pressed to get it to produce a vacuum.
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The weird fan setup is probably blocking the radiator. When your ride was new it would run 24/7 and never overheat on the stock setup so why try to fix what's not broken?

Bugout4x4

They usually only do this at high RPM cold before the T stat opens anyhow. Once they warm up and pressure comes up, you can't make them do this if you tried.

sphinx15

Always room for improvement right? Also when it was new it didn't have a lift, big tires or a big motor... Switched over to the e-fans when I did the motor rebuild, the FF Dynamics setup was a lot easier to package with the thicker radiator.

sphinx15

Also, good to know about the lower hose, probably will replace it if I take it apart this weekend.

97Mudpie

Some have run into that issue running a Flowkooler pump. Personally, I swapped mine in. Either way, an easy pointed question for OP to answer - which he did.

kev4dez

Sphinx, Long story here but maybe it will help, I had almost exactly the same issue on my '99. Although mine was on a stock engine. Started out with a new Mishimoto radiator and new Flowkooler pump. Wasn't trying to solve a problem just upgrading parts. Radiator hoses were fairly new Gates hoses. After a few months time the lower radiator hose ballooned and almost burst, pulled it off and it had came apart/split inside. Didn't think much of it and just replaced the hose thinking it was a bad hose(used new Mishimoto silicone hoses this time). This is when my overheating started,various times and conditions but bottom line it was not cooling like it was previous to the hose coming apart. Now, when I replaced the hose I drained the cooling system and did not see any debris in the coolant. Note: at this point the entire cooling system had been recently replaced, so I was puzzled and then it occurred to me that it was reacting like the system was not able to shed heat. So this led me to a flow issue, I decided I needed to look inside the system and when I pulled it apart and looked inside the radiator through the inlet port I found the problem. The passages in the core were plugged with bits of the cloth reinforcing from the ruptured hose. I tried numerous ways to flush it out to no avail, so I ended up replacing the radiator. Be aware the passages in the Mishimoto radiator are very small, probably to disperse the coolant for better heat transfer, but in my case they plugged up easily. Sorry, this ran on longer than I thought but maybe it will point you in a direction that will help.
Kevin

sphinx15

Thanks for the info and I'll definitely look into it. It does seem like it cools good to a point and then just gives up, once it gets hot it stays hot.

What radiator did you end up putting in yours?

kev4dez

I am putting in another Mishimoto radiator. I am waiting for it to arrive as we speak. I was very happy with how it cooled before the hose issue, which of course was not the fault of the radiator. I previously had the OEM heavy duty radiator and it cooled ok but the Mishimoto dropped the overall temps by about 10 degrees.
Kevin

WyoCherokee

You have a Coolant Flow issue somewhere. that 3-core radiator might be to thick to get adequate air flow across the exchange tubes. My MJ came with a 3 core, and it would always get hot. Switched to a factory XJ Spectra radiator...no more issues i would go back to the stock radiator, fan and a HD clutch, with a shroud and make sure the accessory fan kicks on.

EZEARL

All in all a stock system in top shape and clean coolant passages with a 50/50 mixture seems to be the way to go.

Baddad

dave1123

Thinking out of the box, do you think the coolant is flowing too fast thru the radiator to give up it's heat? Usually this only happens without a thermostat.

sphinx15

I don't think so, when I switched from a stock water pump to high flow I saw no change. Also, I'm getting a pretty big temperature drop between the inlet and outlet of the radiator which seems to me that coolant is spending plenty of time in the radiator, if anything too much time. I did look into coolant restrictors though, wasn't really able to come up with anything concrete.

I did get a chance to "reverse" flush the system this weekend and didn't get much in the way of sediment or debris but it seems very hard to push fluid through the radiator. I don't know what it was like new, but there was significant pressure on the garden hose side when I was flushing it and much much less on the outlet side. I'm thinking I'll grab a stock radiator this week to see if that does it.

Bugout4x4

Again... Does it have a thermostat or not? An OEM thermostat does the same thing as flow restictor. When you start to get overheating issues the thermostat is THE first place to check. And... I have got so many bad T-stats right out of the box new I can't even count them anymore.

sphinx15

Yes it has a thermostat, it's had a couple actually, and checked that it actually opened before I put it in.