87-91 vs 92 - up cooling systems

I'm sick to death of my 89 popping it's top. Do I understand correctly that the 92 + and newer XJ's have a different cooling system design?

An open radiator system like "normal" vehicles, or are they just modified pressurized systems like the 87-91's?

I've been trying to find articles on how to install an open system in my 89.

Thanks.

It's actually 91+

The "new" designs are still closed, pressurized systems.
The only advantage switching to the new design is getting rid of the plastic expansion tank.
In my opinion, the plastic tank is the only issue, and it may be cheaper to replace the tank with a metal unit, unless you are in definite need of a new radiator.

Nope - about 1 1/2 years a go replaced the rad with a new 2 core metal tanks, all new plumbing and new overflow tank and cap.
Since then I've still experienced 3 major boil overs and numerous leaks of small amounts all over the area where the tank resides.

I was reading the tech articles of the people that did the open loop systems and it appears their boil over issues have ended.

You have other issues with your cooling system.
Get those fixed and you will have no boilovers (unless you regualrly drive stop and go in 140+ temps-neither sytem would keep up with that).

Nick

I had the head off my '92 six years ago, and found that the coolant passage at the rear of the head and block was almost completely clogged. I hadn't had any cooling issues, but I cleaned it out, and afterward, and to this day it runs noticeably cooler. I know it's drastic, and I wish there was an easy way to see if this is the problem, but if you run out of ideas, here's a tough one.

So after replacing all parts I can get my hands on - how so I go about diagnosing a no-see-um issue?

Where do I start or how do I start looking and for what?

It's my opinion that there are two major issues with the closed system.

1.) The bottles that most folks have are either aged and cracked or cheap Chinese knockoffs so they crack more easily. The bottles are also a bit taller and when mounted in the same spot they make contact (get pressed) by the underside of the hood. With pressure from within and without they'll crack faster. Moving the mounting point down about and inch should eliminate that problem.

2.) There is no way to positively remove all the air from the system. The two workable solutions I know of are to drill a small (1/16") in the t-stat flange, top & bottom, so that it air-bleeds itself if you're keeping an eye on the coolant level...OR...snag a post 91 t-stat housing with the bung in it for the temp sender and replace the temp sender with a petcock like so:


...or you drop some change on a metal tank, but you'll still have the air issue. You could also use a tank from a Volvo DL or GL, sturdier.

My closed to open conversion cost around $250, all totaled. Don't know if it was worth it but at least I don't have s!@# crakcing on me.

I also got fed up with what I call the exsploding bottle and paying way to much to replace them. I changed mine over to a 91 which is when it was changed. It was simple and cost less than replacing the plastic bottle. after I replaced the radiator,heater control and hoses,I removed the bottle and holder and found an overflow bottle to fit in that area and ran hose to it. Has not been an issue since.

ok check it i just went through this problem. the 87-90 have the old french style cooling system and the 91-01 have the chrysler style. both are ok but im gonna tell u how to fix the problem. listen carefully and dont read anymore posts. my 89 would not run under 220 240 up hill then pop top. i put in an all metal 3 row radiator. new fan clutch. new tstat 160 or 180. and just for the hell of it a went to auto zone and bought a new pressure bottle (reservoir). get the one made by dorman its actually a really nice pressure bottle. mine now runs at 195 up hill in 100 degree heat. in order to get your tstat to work u need the bigger radiator cuz the small one just dont hold enough fluid to allow the tsat to do its job. in te smaller radiator the fluid will just get warm and your tstat will just stick open and eventually all the fluid will get hot. with the bigger radiator the fluid will cool and allow the tstat to open and close. hope u get all sorted.

bails85 said:

ok check it i just went through this problem. the 87-90 have the old french style cooling system and the 91-01 have the chrysler style. both are ok but im gonna tell u how to fix the problem. listen carefully and dont read anymore posts. my 89 would not run under 220 240 up hill then pop top. i put in an all metal 3 row radiator. new fan clutch. new tstat 160 or 180. and just for the hell of it a went to auto zone and bought a new pressure bottle (reservoir). get the one made by dorman its actually a really nice pressure bottle. mine now runs at 195 up hill in 100 degree heat. in order to get your tstat to work u need the bigger radiator cuz the small one just dont hold enough fluid to allow the tsat to do its job. in te smaller radiator the fluid will just get warm and your tstat will just stick open and eventually all the fluid will get hot. with the bigger radiator the fluid will cool and allow the tstat to open and close. hope u get all sorted.

Click to expand...

Somebody has got some real B*LLs for a person with 4 posts. :twak:

You have a few errors ( miss statements, or wrong ideas, not sure which) in your post, but some of your advice is good too. Don't take my statement the wrong way. Nothing wrong with tossing out your thoughts and trying to help (don't stop), just don't go telling people to ignore the rest of us unless you really have big B*ALLs, or really know your sh*t, which you don't, yet.

The 87-90 system is called a closed system, partly I guess because everything is sealed under pressure including the POS plastic bottle / reservoir that we all are so fond of:laugh3:. 91-2002, jeeps, have what is called the open system because the overflow bottle is not under pressure, it is outside the pressurized system.

If you have an engine that has a problem (bad O2 sensor, bad partly clogged injectors, ... making it run lean) , and is running too hot, it won't matter what system you have. IF everything is working perfectly, the Renix (87-90) system is a god system, but the current POS bottles on the market have some issues. The bottle caps are weak. That can be solved with a worm gear clamp on the outside of the bottle cap See my "Renix Bottle" cap thread for details. Lowering the shelf about 1" helps with the crushed bottle issue mentioned below.

But if your engine runs too hot, or the radiator is old and clogged some, or both, the bottle is the week link, and will fail first.

There are a number of outstanding thread discussions about all the causes of overheating, and how to test them. To get up to speed look for threads on overheating, head gasket leak, oxygen sensor, fuel injector problems, compression problems, radiator problems, thermostat problems, temperature sensor problems, ZJ fan clutch upgrades, Efan thermal switch (In the radiator), dying water pumps, or water pump seals, and even bad temperature sensors lying to the dash gauge.

But back to the OP, if all your problem is, is the cap coming loose, the solution is way easy, a worm gear clamp.
To switch to the open system (91-2002), you must buy a 91-96 (not sure if 97-2002 is exactly the same or not) radiator with a filler neck that uses the standard radiator cap, or install an inline filler neck that uses a standard radiator cap, in the upper radiator hose. (one like the ones JEG.com sells), then add a standard open bottle, and connect the hoses at the old bottle with out the bottle.
There are some nice threads with pictures here from prior years that show the closed system to open system swap, in its various forms.

That said, many of the new cars, still use the closed system, they just have better bottles that have better shapes, like the 96 Ford Taurus.

Here is link to the most recent Renix Bottle cap and clamp debate!

http://www.naxja.org

ECOMIKE - You bring new hope mate - Thanks.
How I miss those threads eludes me.... I will first do your worm gear fix, but I think I need to lower my moutning plate for the bottle, I may have some contact issues.

If that's the case there may be stress cracks on the bottom, should that be the case the Mac's aluminum bottle is my next step.

I'm also thinking of putting a FlowKooler high volume water pump and matching t-stat also.

I figure it's easier to add $200 worth of parts and my labor vs: bying a newer / differenet vehicle.

Thanks.

bails85 said:

ok check it i just went through this problem. the 87-90 have the old french style cooling system and the 91-01 have the chrysler style. both are ok but im gonna tell u how to fix the problem. listen carefully and dont read anymore posts. my 89 would not run under 220 240 up hill then pop top. i put in an all metal 3 row radiator. new fan clutch. new tstat 160 or 180. and just for the hell of it a went to auto zone and bought a new pressure bottle (reservoir). get the one made by dorman its actually a really nice pressure bottle. mine now runs at 195 up hill in 100 degree heat. in order to get your tstat to work u need the bigger radiator cuz the small one just dont hold enough fluid to allow the tsat to do its job. in te smaller radiator the fluid will just get warm and your tstat will just stick open and eventually all the fluid will get hot. with the bigger radiator the fluid will cool and allow the tstat to open and close. hope u get all sorted.

Click to expand...

Well, jeez. Thanks for clearing all that up.

I guess everything I've read here and experienced myself is just a bunch of crap.

ParadiseXJ said:

Well, jeez. Thanks for clearing all that up.

I guess everything I've read here and experienced myself is just a bunch of crap.

Click to expand...

Ya think?

:roflmao:

RTFM

My second set of wheels, back in 1976, was a 400 ci, 4 barrel QJ, Chrysler lean burn, designed to run hot. I got a lot of experience with trying to keep hot running engines from boiling over with that beast.

In summary, if their is something on the engine side adding excess heat, lets say too much excess heat caused by the engine running too lean, or a hidden, disguised gremlin style head gasket leak, it needs to be located and fixed. In my experience, one starts with the cooling system, and at some point we run out of things to try on the cooling side, and switch to looking for excess heat problems in the engine.

Given a limited budget, I always start with just fixing leaks, bottle, hoses, water pump, head gasket, radiator, where ever obvious leaks are found. Then look for the hidden leaks! (Those are the fun ones!)

Then I check the air flow, replace the fan clutch if it is running slow. Then if needed, I go for the biggest bang for the buck, which is usually a new radiator, if the old one is over 4 years old, or a rod out of the old one if it is a true 3 core, all metal, brass-copper radiator.

Usually a thermostat fails in the closed position, and is quite obvious. I suspect 90% of replaced thermostats were a waist of money. Water pump failures are usually obvious too. I don't recall reading anyone here, who singularly solved their overheating problem with a beefed up water pump, or thermostat.
Unless you are making mods, and adding excessive loads to the cooling system, like towing, long up hill drives, in 100 F weather, and off road stuff that increases cooling requirements, I see no need for fancy thermostats and water pumps. Just get the best radiator you can, which is currently by most accounts, the 3 row all brass, copper, CSF radiator for about $165.

In 36 years I have never had a thermostat go bad, and only lost 2 water pumps, in over 1.2 million miles.

And while diagnosing your problem, watch your oil, coolant, and tranny fluid for color, viscosity and pressure changes caused by inter system leaks!

Ecomike said:

My second set of wheels, back in 1976, was a 400 ci, 4 barrel QJ, Chrysler lean burn

Click to expand...

Ahhh..yes! Glowing red exhaust manifolds, warped ThermoQuad fuel bowls, and spark computers! I can remember the Chrysler tech looking at me with a straight face, explaining " naw, that's not pinging, we call it the sound of ecomony!"

They sure don't build 'em like they used to! LOL!

Back OT: I still have the closed system on my '87, and like mentioned before, if properly maintained, it works well.

MJmk said:

Ahhh..yes! Glowing red exhaust manifolds, warped ThermoQuad fuel bowls, and spark computers! I can remember the Chrysler tech looking at me with a straight face, explaining " naw, that's not pinging, we call it the sound of ecomony!"

They sure don't build 'em like they used to! LOL!

Back OT: I still have the closed system on my '87, and like mentioned before, if properly maintained, it works well.

Click to expand...

I actually had glowing red manifolds on my 73 Ford LTD, back in 1998 (351, 2brl, sold it 2 years ago finally with only 87,000 miles on the ODO! Still used straight 30 wt oil). The centrifugal advance on the distributor was rusted and locked up. I popped the hood one night, 40 miles from home, just 5 minutes after starting it up, getting ready to head home from graveyard, and freaked out:shocked:. That was when I figured out why I was going through exhaust manifold gaskets. It only glowed at night. IR gauge would have been handy back then!

What would cause the red exhaust- clogged cat? Timing too retarded? Lean carb?

No cats back then. We're talking the good old days. '71's were the last good motors. Premium leaded gas. My 429 was 365 horse. In a Grand Marquis wagon. Then they leaned the shit out of them and retarded the timing. And the V8's dropped to more like 100 HP.

Get a new bottle and cap from Morris 4x4 Center (they're a sponsor, and have parts for a decent price) and replace the wretched thing. It's not a "lifetime" part, whatever everyone has you think. Write the date you install it on the tank with a Sharpie pen, and start checking it again after five years (five years isn't bad - ten years is better. I wouldn't push it much past that.)

Also, it's not a bad idea to keep a spare cap in the glove box or centre console - it's only a few bucks more.

Keep an eye on the hoses - if your heater hoses are still held on with the aluminum crimp sleeves, start thinking about replacing them. I've done away with most of the rubber in the heater circuit (pic on my site) and replaced it with sweated copper with good results.

Those are the big points I can think of. Drilling the thermostat was originally my idea (you'll find plenty of posts here by me about it,) and it's worked well for me for years. You can also get the block nice and full if you slowly pour coolant in by way of the thermostat housing, if you're having trouble. Just give it time to filter down into the block between pours - should only take a few seconds.

The drilled holes are to make the system purge itself of air - the lower one passes coolant into the block, the upper one passes air out of the block.

There's really nothing intrinsically wrong with the "closed" cooling system - I've got the same system on my 2005 Suzuki Verona, and had it on my 1992 Chevvy Corsica. I've owned five RENIX XJs, and the one that ran hottest was the one that had already been converted (I was seriously considering converting it back to the closed system - since it seems to be more efficient after all, when properly maintained.)

heyhar said:

What would cause the red exhaust- clogged cat? Timing too retarded? Lean carb?

Click to expand...

Late spark caused mine. A leaking exhaust valve does it too I think. Basically a LOT of fuel ends up burning inside the manifold, instead of the block/head area.