I missed the last of the 85ºF and warmer days of this Summer, but I did get some tests conducted.

I tested the two radiator caps I have -- the Mopar one that was replaced would not hold any pressure and the new Stant/Motorad would only hold 13psi even though it's rated for 16psi. I'm likely going to replace it with something else, but I haven't decided on brand since Mopar discontinued theirs.

I put the Mopar 195º thermostat back in along with draining the Supercool and going with Prestone + Water Wetter and the HD fan clutch. It's hard to say if there was much impact given I only had an 82º day to perform the drive test with instead of the previous 91ºF, but there wasn't anything dramatic with the results:

• HD/ZJ fan clutch, thermostat, WaterWetter
  • 65mph cruise
  • OAT 82°F
  • Partly cloudy
  • Water temps
    • 208° with heater on southbound, 208° with nothing on southbound
    • 215°F with AC on northbound
    • 221°F idling with heater on
  • Air temps
    • 129° IAT northbound, 138° southbound
    • 142° engine bay northbound, 135° southbound

I also noticed a big drop in power from the HD fan clutch utilizing the butt-dyno. It got me wondering how much of an engine load impact it makes. So, in a single day, I performed the same drive test with the HD fan clutch and with a brand new stock fan clutch. There was indeed a difference in load:

• HD/ZJ fan clutch, thermostat, WaterWetter
  • 65mph cruise
  • Engine Load 27-38%
    • Northbound
      • A/C off
      • Average 30-32%
    • Southbound
      • A/C off
      • Average 27-29%
• Stock fan clutch, thermostat, WaterWetter
  • 65mph cruise
  • Engine Load 24-36%
    • Northbound
      • A/C off
      • Average 27-30%
    • Southbound was a bust because traffic prevented me from maintaining 65mph

Since I didn't see any noticeable engine temperature differences between the two clutches, it makes me think the additional air the HD clutch pulls in for cooling does not (significantly) outweigh the extra heat generated by the increased engine load. I did not test at crawl speeds as that's not the cooling scenario I'm trying to resolve. I would venture to guess the HD air flow to engine load ratio would be favorable at the lower speeds.

This was performed back in August with unfavorable results. I found it did nothing for engine cooling at any speeds and very little to engine bay temperatures.

Given Summer is over and we now have cooler weather until April, I'm going to hold off on spending money on a radiator. I think there's still a debate on whether a bigger radiator works better for strokers as someone with the Golen stroker in their XJ reached out to me stating they put the stroker in with a brand new single-row Spectra radiator and they've had much better cooling results with a BIG Ron Davis radiator. So, I've got all winter to decide.

Until then, I do have a few other plans:

1. Have the efan triggered to come on at 200º and off at 195º instead of waiting until the factory 218º
2. Look into extending the fan shroud and sealing the bottom of it around the radiator better
3. Install a remote oil cooler

 

I've been following this thread since it was started. I wanted to see where it wound up. I can't take it anymore.

What you need to do is return your cooling system to complete stock configuration, after doing a complete flush of the cooling system. No fancy shrouds, no 3 row fans, no multi core radiators, no caps with release levers, no high flow pumps, just a NEW refreshed stock cooling system. Use 50/50 antifreeze/distilled water. Don't use parts that are old, like the radiator itself, just buy everything at O'Reilly or Vatozone, or Napa, or wherever. This should be all that's needed to keep everything in check.

I did exactly this when I put my 4.6 in years ago. I lived in the SoCal desert where temps routinely are triple digits for months on end in summer, and mid to high 90s during spring and fall days. Never have had an issue, with one exception of an efan that crapped out on a trail run at the Hammers a few years back, seized motor bearing. Replaced and perfection. Done occasional flush and fills since then, and that's it.

The stock cooling system is more than enough to keep it running. Time and neglect are the 2 biggest killers of the cooling system.

Also, a lot of the temps you posted don't seem out of line to me...things are going to fluctuate and you're not going to have perfect numbers. Ballpark is fine, a +/- of 10* isn't a show stopper, as long as everything is operating properly.

Just my .02.

 

What he said...

 

@roninofako Thanks for posting your experience with a stock cooling system and a stroker as it does give me some hope. It sounds like to me you have joined the camp of questioning the efficiency of the radiator. You mentioned you "never had an issue," but what was the average weight of your XJ during that time and what coolant temperatures were you experiencing in SoCal?

I know the forum is littered with people saying 210º is the normal temperature for these blocks and 220º is not a problem, but I have a hard time believing the Jeep engineers designed the motor to run 15º above thermostat temperature hoping the external elements will keep the temperatures at bay. This is why I seek to get down to where the thermostat is regulating the temperatures. A month ago I could not pull a 10,000-foot pass in 75ºF weather at 55mph in third gear in one shot as I hit 240º with the heater on and had to pull over. I wasn't towing, but I was at GVWR. This should not happen.

So, to continue the friendly debate of radiator size:

The only non-Mopar parts I currently have in the cooling system would be the Stant cap and Napa fan clutch (non-HD) because Mopar discontinued both of those parts. Yes, I use a bigger radiator, but it's the Mopar tow package radiator because my XJ is normally heavy (see first post) and I tow. So, if a smaller radiator in the XJ outperforms any bigger radiator in all scenarios, then why did Mopar include a bigger radiator in their tow package? I have trouble reasoning this one out.

Another lingering question I have that is contributing to my hesitation to "just replace the radiator with a new one" is regarding lifespan. What lifespan should be expected out of an XJ radiator? It seems to me one should last more than 6 years and 30k miles. When the stroker was put in, the coolant was due for replacement at that time anyways and it was a bit brown, but nowhere near caked and sludged like I've seen pictures of on this forum. It simply looked like a normal time to be flushed. In addition, with the several flushes I've done in the past five months testing different things, it's come out clean every time. Wouldn't this mean the radiator is close to sediment-free? I have yet to replace the radiator in my other 17-year old vehicle and its cooling system is functioning fine with flushes per the factory schedule and its motor was even replaced (granted it's not an XJ with a big motor, but my point is it's lasted 17 years and 240k miles).

I seem to read a lot of varying results with strokers and cooling systems across multiple sites. Some say nothing more than a "stock system" is sufficient for 120ºF weather. Others say a stock system is not adequate enough and x, y, and z ought to be done to achieve 195ºF in any temperature. Given the large spectrum of results, I think there are factors (data points) left out in people's setups that may or may not contribute to their success which is why there are many threads on the topic. This is why I'm trying to provide details, document everything, and ask questions to better understand and test based on my parameters and maybe it will help someone later on. I'm also starting to wonder if a Golen stroker runs warmer than others...

 

I don't know why the weight of my XJ would matter, but I will play along. I used to work at a trash processing facility and they had drive on scales. My XJ, unloaded, with me in it, was just shy of 5200 pounds. (For those wondering why so much, full stiffeners front to back, winch, custom bumpers, sliders, solid arm 3 link and steering, 35s). Fully loaded for camping/wheeling add 500 pounds as I carry tools, spare parts, fluids as well as food, drinks, gear, etc. Like I stated above, the temps in the area I lived in for the majority of the year (7 months) is 90-110*+, a couple of months (1 in spring, 1 in fall) where it's 65-75*, and the rest winter months that vary from below zero to 45*, temps can fluctuate wildly in the desert, with even some 90* temps from time to time. But the majority of the time, it's simply hot as *****.

I daily drove to work out there, and saw everything from stop and go city traffic, to freeway/highway miles, to trails from fire service roads to The Hammers in JohnsonValley, (serious off road crawling), and everything in between.

As far as coolant temps go, I couldn't tell you. The dummy gauge in the cab has never spiked, except for the one time I lost my electric fan on a wheeling trip at the Hammers, which once it spiked, I pulled over immediately, figured out my problem, let it cool down, and got out of the hills we were in, legged it to Napa, replaced my fan, and drove home...cut my wheeling trip short, but I didn't want to tempt fate that day as the ride home was about 50 minutes.

Answering the question of longevity, it all depends, but at 6 years, if you're having issues, replace it. It might flush clear, but passages and especially corners are probably blocked with scale and sludge that won't get knocked loose. Like cholesterol clogged arteries.

The reason there's so much misinformation about the XJ cooling system is people have issues, then band aid it instead of revamping the whole system. They overheat and replace a WP. Or, a radiator. Or whatever. They then decide to "upgrade" the component with a 3 core aluminum radiator, or a high flow pump, and might make their problem temporarily better, and hence the stigma of more is better. Only to have another problem 4 months later.

I've been on this site a long time, and see it every spring/summer "HALP IM OVERHEATING" threads abound. I have always given the advice to just buy everything brand new. Hoses, clamps, everything. It really doesn't cost that much to just replace the whole system. I understand everyone has different financial situations and not everyone does their own work, but I have never heard from anyone who did an entire cooling system revamp and still have issues. Cracked heads don't count, lol...that's completely different

Everyone complains the cooling system is garbage. I beg to differ. When properly maintained, I've pushed it well beyond stock limits, and it's held up just fine.

P.S. I can say the same thing about the ignition and timing system. Everybody starts talking tunes and ignition upgrades when it comes to running a stroker. Both these are also completely stock on my rig. Never an issue and my motor runs boobies.

 

This matter has been debated at length on the Oz forum, and the FSM makes it pretty clear that is the case, so have a read of that for enlightenment

I have spoken to engine experts that think these temps are too high, and others who say it is fine

afaic, its engineer design factor is to decrease fuel consumption and pollution

I agree with Ron, and said so in post #31

I once read a formula that is the best to flush out old blocks, which consisted of some acid I cant recall, followed by a chemical that is the same as one used to flush dishwashers, then a neutralizing compound. When I tried to purchase the named chemicals from Industrial suppliers, they refused and treated me like a drug dealer or terrorist. Old blocks get very clogged with rust, scale and sediment

It does sound like your cooling system is not working at optimal, so if you have a further issue when weather gets hot, I reiterate that going stock is the easiest cheapest baseline to start with

 

Thanks for playing. Weight matters to me because engine load is affected by it and the higher the load the more heat can be/is produced. Your account sounds great, but I do still wonder what temps your coolant was actually at. On my gauge, halfway between the 210 mark and the next mark is 230° according to the computer and IR gun readings. I’ll be considering your suggestion and information.

I have read the cooling system section of my FSM multiple times in the last five months and nowhere have I seen it say the engine should normally run above 195°. I’ve even used the search feature of the ebook. Do you have a page number or section to reference? Perhaps it’s different for your 1996.

 

The 195°F rating is the temperature at which it starts to open. Google indicates that a 180°F thermostat may not be fully open until as much as 20°F above the set point. Not suggesting this is a hard and fast rule, but it's not much of a stretch to say that the thermostat isn't even fully opened until at least 205°F.

While I'm at it, regarding the cheap, parts store radiator suggestion, if you take a look at Rock Auto, even the cheapest radiator for a 94 XJ is listed as "2-row equivalent". Over the 30+ years since AMC shoe horned the 4.0 into the XJ platform, at lot of improvements have been made in heat exchanger manufacturing. An XJ radiator can only be 1-1/4" thick without affecting the e-fan and shroud. A modern 1-core radiator has a 1" wide core, giving 1" of contact with the cooling fins. A 2-core of old likely had 2x 1/2" wide, or so cores; need space in between so 2x 5/8" won't work. 2x 1/2" yields the same 1" of contact with cooling fins, but then the downsides of a 2-core come into play. A 1-1/8" or 1-1/4" wide core flows less air than a 1" wide core, all else being equal, plus the 2nd row doesn't cool as well as the first row due to the warmer air it receives, plus the passages are narrower, making them more likely to clog. Add the 6 years of corrosion, both internal and external, that your radiator is wearing as insulation... Google brings up suggestions to clean your home's HVAC condenser yearly, even to the point of an acid wash to remove external corrosion.

One thing I noticed that peaked my interest was the increase in temperature after installing the ceramic coated header. Are you running lean? How many miles do you have on this? Most-any newly rebuild motor will run hotter than the worn out one it replaced until it wears in.

 

My understanding is thermostats aren’t binary devices being either fully opened or fully closed. Their job is to regulate the temperature. So, a 195° thermostat will start to open at 195°, but under normal conditions, it should have small adjustments (open a little, close a little) to maintain that 195. If it’s constantly wide open, it’s no longer regulating the coolant temperature.

Interesting points about radiator advancements that I’ll think about.

It was some time after the header swap when I started noticing sky conditions significantly impact the cooling ability. I think the header test was with severe sunny conditions and the one prior might’ve been cloudy. After that I tried testing with sunny conditions.

I’ve thought about the mixture before and I believe as long as the injectors can provide enough fuel, the O2 sensors will tell the ECU to adjust the mixture appropriately. Based on another conversation, I’ve recently monitored my LTFT and see that the numbers are flopping between negative and positive based on my throttle position and look to be normal. The motor has about 4,600 miles on it now. I could tell during the first 500 miles it was tighter and more responsive to throttle changes than it is now, so your point about additional heat during break-in would hold some merit, especially with the break-in oil allowing wear to take place. But, I’d think after several thousand miles it’d be broken in now.

 

Many people completely ignore the block passages, and to do so is idiotic. There's passages in there you're never going to get at. Whrn the motor is out, on a stand, some of those passages are easier to access (but not all) and I definitely recommend cleaning as much of those areas as possible by chipping, scraping, whatever. You'll be surprised how much junk you can get out of there.

Your statement about using different chemicals to help is all part of a proper flush, there's a ton of home brew methods for this, and a handful of products you can purchase from your local parts store. You fill the system with these chemicals, run the motor for a bit, then drain and flush again, then fill with coolant. I'm with you 1000%.

 

Why do the temps matter when it's working as intended? IMO you're overthinking it. Besides, the dummy gauge is notorious for not being precise, it's ballpark at best, but it does what it's supposed to do when working as intended, spiking to indicate a problem.

I DGAF about the numbers, because my junk works...and when it doesn't it tells me, then I fix it. I've replaced my cooling system twice in my jeep, once after I bought it, and again when I swapped in the stroker.

Results don't lie.

 

Anyway, you know what my opinion is, and I suggested what I would do if it were me. I got nothing else. If you decide to heed that advice, let us know if it works. Otherwise, I'm out. Good luck sir.

 

The thermostat only sets the minimum temperature. Above that, the temperature at any given moment will be whatever the energy balance works out to be; the thermostat really doesn't have a whole lot to do with it. For example, if you're engine is running at 210°F or 215°F and the 195°F thermostat is wide open at that point, it doesn't matter if you put a 160°F model in there, it's still going to run at 210°F. Now if the overall energy balance is such that the temperature can drop below 195°F at times, a lower thermostat temperature can give you a bit of "reserve" so that it doesn't overheat as quickly. An XJ cooling system is really only considered not up to par if the temperature keeps going up after the Aux Fans kick on at 215-218°F. Needing to turn the heat on is not normal...

Lots of variables in testing. Quick math suggests that it's about 9 ohms per degree at 212°F. Have you checked the accuracy of your CTS reading using boiling water?

O2 sensors only come into play during cruise. Above a certain throttle position, it reverts back to open loop and goes solely by the tables. Honestly not sure where that is exactly, but I question if 55 mph in 3rd going up a 10k ft mountain wouldn't be mostly open loop. I drive over a couple PA mountains fairly regularly and to be limited to 55 mph in 3rd, it must be really steep or you're really loaded down. I've pulled a 24ft pontoon boat with mine many a time over some really big hills, so I'm not completely ignorant of what it takes to slow an XJ down. 1st gear at ~25 mph, pedal floored and still slowing down to get through one particular section. On a different route, there's a section that my 4-banger beater w/ a heater doesn't have enough power to maintain speed and you have to rev the 5 speed manual out in 3rd, completely empty, just me, but I've pulled a loaded 10 ft utility trailer up it with my XJ, two people, full hatch of gear and it powered right up it no problem up it in 3rd. 4.0L, AW4, 4.10s, 31s in my case. Just trying to get some context... Sure it runs hot. Yeah I turn the Aux Fan on before I even hit that "1st gear at 25 mph" section. But it has never overheated.

One benefit of a modern radiator is they made the tube walls extra thin, causing them to corrode through and leak quicker. It's been my experience that they'll spring a leak while loaded up with co-workers heading out for lunch well before the performance degrades to the point of overheating... Buy cheap, replace it every 4 years or so, life is good...

 

I have not performed that test, but I have measured the temperature of the thermostat housing with an IR gun and it's always been quite close (2-3º) to the OBD2 values.

I looked up the pass stats. The pass is a 7% grade for five miles with 2,000 feet of elevation gain from 9k-11k. I started it in 5th at 65mph and quickly dropped to 4th maintaining 60 for a bit and then dropped to third when my speed dropped to 50mph. I would've been above 3k RPM at that point which is about when I've seen my LTFT sit at 0 so you likely are right it was in open loop. Yes, I was at GVWR.

Replace every four years? This sounds like a terrible way to live.

 

I hear ya hoss. It certainly would be nice to have a good solution. A decade ago, there were more options. I splurge like crazy on my XJ and tossing $120 or so at it every other coolant change is cheap insurance for never having a cooling system issue. Compared to the cost of a $300 or $400 high end solution, on a $$/yr basis, it's not too far off par. I also throw on a new pump and a new thermostat, because well, "it's cheaper than replacing the coolant if it needs it later". I probably got 6 years out of that cheap radiator, while never changing the coolant once, so it corroding through was probably half my fault. Replacing i every 4 years is probably a big exaggeration. The internet and sarcasm, ya know... I wish I could with confidence tell you that there's another solution that will solve your problem with absolute certainty. Suggesting the cheapest solution is the least risky to me.

There's a whole list of things that could be causing it to run hot, ignition timing (set by computer), cam timing (hopefully checked by builder, but probably not), cam profile (hopefully they picked a good one), etc. Can't really suggest you try another motor, or put it in another vehicle. A different stroker builder has a bad rap for running hot due to poor cam selection/timing. If you can get the cam specs, perhaps reach out to Russ Pottenger over at Jeep Strokers, or the community in general, and see if he has any thoughts or history with your brand of stroker.

I try to remember that they all just big hills around here, but some of them really do seem like mountains, but I don't know that any of them are a 5 mile climb. The "25 mph in 1st" route gets to 12° for about 200 yards that just kills vehicles of all kinds and the other route that my beater hates is 10° for a mile or so.