90 XJ HELP ME PLEASE!!!!!!!

here's my problems. About 8 months ago I picked up a 90 cherokee 4.0L 4 wheel drive 125k miles for $750 (friend of the family kinda deal, been sitting for a bit and wanted to get rid of it. Guy said the electric fan was bad on it. No big deal. Brought it home. Did a quick fix to the fan and hooked it up to a toggle switch. Next day went and got a 3" lift for it and some 31's on some rims. (Small I know, got it to be the girlfriends rig). Ok so we started heading out to a jeep show. On the way there it over heated like 6 times. No biggie I didn't care. Well I pulled the head and got it milled. They took .015 off of it. So I put it back on. Then did some research on the Renix cooling system. Didnt like what I was seeing so I replaced everything ( One of the perks of working at a shop, get parts cheap lol). Brand new radiator, overflow bottle, water pump, radiator cap, hoses and thermostat ( open cooling system set up from a newer style cherokee.). So I got it all together. Started driving it around and the gauge is reading hot again and it was pushing coolant through the radiator cap. I figured it was a bad motor and didn't wanna waste my time trying to figure it out. So I had a parts jeep with a perfectly good motor in it around the same miles. So I replaced the motor with the new known good one. Start it up. Running good for about an hour than started doing the same thing ( Pushing it through the cap). Noticed the heater control valve was sticking. So instead of replacing it. I just removed it and looped the hoses together for it to run straight through without restrictions. Still doing the same damn thing Next I removed the thermostat. Same thing. I'm kinda lost here. I don't mind doing the work but the repetition part is anoyying. The girlfriend loves the car she doesn't want to get rid of it so I'm trying to get it working.

Any suggestions will be appreciated!!

**NOTE**
YES THE WATER PUMP IS THE RIGHT ONE AND THE FINS ARE THE RIGHT DIRECTION. I TRIPLE CHECKED.

THANK YOU I ADVANCE

You work for a shop? Remind me to never bring my jeeps where you work... you are throwing a lot of big expensive parts and fixes around with (as far as I can tell) zero debugging. That's not a very good way to fix things...

Did you make sure you burped the cooling system properly? Is there a coil spring in the lower rad hose to prevent it collapsing under suction?

Yes I work for a shop and 2 i don't care weather or not you bring your shit to my shop. The cooling system cost me a total of $100 cux of the perks I have at work. Also in my posting I said I read about the renix systems online and how many problems they had so either way I was gunna replace the cooling system. So instead of criticizing me on what I did with my vehicle I'd appreciate it if you could help me fogure out my problem. That is why I made the post after all.

Thank you.

I did burp the system. And there is no spring the I'm the lower hose from what I can tell.

If you can grab the bottom hose halfway between the radiator and the water pump and squeeze it together with your fingers, it is likely to give you grief.

Some hoses are stiffer than others, the water pump seems to suck better than it pushes. I learned the hard way to always make sure the bottom hose has a spring or is made with a built in coil and/or the ribbed style. Getting the spring in the hose is a pain, tie a piece of string on the end and pull more than push. If it is still difficult use some plumbers silicon lube. The Jeep dealer usually cuts the spring into three or four pieces and shoves them in there, the last time they did that to mine one of the spring pieces migrated into my water pump.

Did you get a single row radiator or double row?

Any kind of trapped air in the block messes with the flow. The open system is easier to burp, most times I just rev it with the cap off and the air moves to the top pretty quick. You can also squeeze and release the top hose 5 or 6 times and usually get most of the air to move into the radiator where it can vent out of the cap opening (filler neck), the rest usually finds it's way to the top on it's own when the motor goes through a few hot cold cycles and spits the air into the recovery bottle.

You said it was pushing coolant through the radiator cap? Into the recovery bottle? Or spewing out of the cap? Is it possible you have the wrong cap? The reason I asked is the only dumb question is the one you don't ask, IMO, just covering all the bases. I must have replaced a hundred thermostats and somewhere around number 75 I put one in backwards, snit happens.

Thank you very much!! I checked the lower hose. And it does have a spring in it.. I had got the single row radiator. I fileld rhe system when the engine was not running. Tried burping it like that for a few minutes. Than I turned the motor om amd the level drop so I kept adding 50/50 mixture. Eventually tje level got to high and was pushing out the filler neck. I than put the cap on it. After while it would push it out the cap omto the ground. Not into tje over flow tank. It could be possible I got the wrong cap. As far as the right cap but the wrong pressure. Amd I totally agree with that comment!!. Thank you for answer my post!!

You may have some air still trapped.

Find a place where you can park NOSE-UP WITH THE RADIATOR CAP BEING THE HIGHEST POINT.

Let the engine cool BEFORE removing the radiator cap.

Once the cap is off, start the engine and let it warm up fully--about 20 minutes--any air should find its way out by then. Top off the system as it runs. Once the engine is fully warmed up and you believe all of the trapped air is gone you can cap the full radiator, then fill the recovery bottle to the "HOT" line.

zjmech17 said:

It could be possible I got the wrong cap.

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Get the same cap that the computer guy at the parts store said to get...only make sure it's a 16# cap....even if they tell you it takes a 13# cap. 13# is weak, 16# better.

Look at the radiator filler elbow/neck really closely. Seems every second radiator I get (UPS) the filler neck is bent during shipping. You may have a ding in the top of the neck so the top seal (gasket) in the cap isn't sealing. Or underneath were the ridge slopes so it cinches the top seal in the cap down tight (kind of a cam action). I've also seen the stops for the cap get bent on the filler neck so the cap doesn't tighten all the way.

The radiator cap seals in two places the top seal is always sealed the bottom seal is spring (pressure) loaded.

An old style radiator cap, back before coolant recovers systems, is unlikely to seal right, top or bottom, though it may fit (kind of).

Sorry I didn't get back yesterday! I was moving into my new apartment. But thank you all for the tips. I will check out filler neck today. Nope its not cracked or anything. I'm just gunna get a new cap for it cuz there cheap. In a couple hours. Ill bring it into the shop and put the front ekd on the lift and lift it up a little bit sooall the air moves to the hhight point. Hope this fixes it!! Thanks guys I really appreciate it!!

kastein said:

You work for a shop? Remind me to never bring my jeeps where you work... you are throwing a lot of big expensive parts and fixes around with (as far as I can tell) zero debugging. That's not a very good way to fix things...

Did you make sure you burped the cooling system properly? Is there a coil spring in the lower rad hose to prevent it collapsing under suction?

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This thread is going to get interesting!!!! Lets rename it how to maximize the cost of fixing a cooling system at a local shop?, LOL where is Bimmer when we need him? LMAO

I am going to LMAO if the problem turns out to be an exhaust leak blowing on the block, a lean condition (O2 or injectors, or manifold), or just a bad fan clutch, or no fan shroud, or mud in the condenser in front of the radiator....or...

I am curious what radiator he bought?

But alas, maybe 8Mud hit it with the radiator cap issue. I got 4 bad ones of the shelf once, all tested bad on the tester. Two of them had flaws in the top seal!!!! It was back in 2007, and qulaity has gone down hill since then.

take the 5/8ths hose off the water pump nipple and fill it with antifreeze, they develop air pockets there and will overheat if it isn't taken care of, basically the water pump is cavitated and just running with air at the impeller

Thanks jnida63 ill try that. As far as you guys saying how much it costs to replace the cooling system idc. I did it to get rid of the renix set up

fixed my 90 xj the same way as you, replaced everything including heatercore, had no idea on condition of these parts when I bought the Jeep, was told by previous owner that he had problems with overheating so I new it in advance, any way, my jeep would still overheat at highway speeds after replacing all those parts, added a trans cooler , PRESTO!!! no more issues in two years , hope I helped you with another possibility, good luck with the project

zjmech17 said:

Thanks jnida63 ill try that. As far as you guys saying how much it costs to replace the cooling system idc. I did it to get rid of the renix set up

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I have three running Renix jeeps with no cooling problems using the closed Renix cooling system. One has 279,000 miles on it. Most newer cars use the same closed system as Renix with no problems, including my 1996 Ford Taurus and 2001 Saturn. There are significant advantages to the closed system.

I completely agree with getting rid of the renix system simply because it's annoying to bleed. I was just saying you should stop throwing parts at the problem and debug it

I suspect you have a bleeding/air pocket issue - hopefully the water pump/heater hose idea will fix it. I have seen a lot of jeeps with a bleed valve/fill port installed in that hose, haven't bothered to put one on my jeep yet but next time I see one at the JY with it, I'll probably be swiping it and doing so.

Ecomike said:

I have three running Renix jeeps with no cooling problems using the closed Renix cooling system. One has 279,000 miles on it. Most newer cars use the same closed system as Renix with no problems, including my 1996 Ford Taurus and 2001 Saturn. There are significant advantages to the closed system.

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awesome. Wel I'm sure you treat yours right. Apparently the guy I got it from didn't treat his right and I read thebproblems that the renix system has and I replaced it. End of story. I don't see how you making this comment helps with my problem. So I kindly ask you GTFO.

kastein said:

I completely agree with getting rid of the renix system simply because it's annoying to bleed. I was just saying you should stop throwing parts at the problem and debug it

I suspect you have a bleeding/air pocket issue - hopefully the water pump/heater hose idea will fix it. I have seen a lot of jeeps with a bleed valve/fill port installed in that hose, haven't bothered to put one on my jeep yet but next time I see one at the JY with it, I'll probably be swiping it and doing so.

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Thanks im hoping its just an air pocket.

fulltimer said:

fixed my 90 xj the same way as you, replaced everything including heatercore, had no idea on condition of these parts when I bought the Jeep, was told by previous owner that he had problems with overheating so I new it in advance, any way, my jeep would still overheat at highway speeds after replacing all those parts, added a trans cooler , PRESTO!!! no more issues in two years , hope I helped you with another possibility, good luck with the project

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Thanks for the idea ill.look into that. What trans cooler did you use?

zjmech17 said:

awesome. Wel I'm sure you treat yours right. Apparently the guy I got it from didn't treat his right and I read thebproblems that the renix system has and I replaced it. End of story. I don't see how you making this comment helps with my problem. So I kindly ask you GTFO.

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I'd apologize and chalk it up to having a tard day, you are likely to need Mike again way before he needs you. Bring rude isn't likely to be productive in the long run. Mike is a problem solver and pretty good at it. he has helped me on numerous occasions and saved me many hours of troubleshooting a problem he has already solved.

I have both, the closed and the open system. Either, well maintained, is marginally acceptable. Some of us get a kick out of making the closed system work, when it works it works well. Both systems have high spots that trap air.

I learned a long time ago, even the dumbest guy in the room is going to have good idea sooner or later and the only really dumb one is the the one who refuses to listen.

I do pretty well troubleshooting electrical systems (over fifty years of practice), most would make an XJ look like a toaster. Mike has helped me out and steered me in the right direction many times. It took a team of engineers to engineer the XJ, hard for one guy to know everything. I've also found it smart to learn from the others guys mistakes, a lot less painful (expensive) in the long run.

New isn't necessarily better, I've had a lot of new parts fail quickly or perform poorly. Even OEM parts in many cases aren't what they used to be.