89 XJ coolant flush and cooling system upgrade - JeepForum.com
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post #1 of 33 Old 06-20-2017, 05:12 PM Thread Starter
al_xv
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Xj 89 XJ coolant flush and cooling system upgrade

Due to recent overheating issues, I've decided to do some cooling system work. I believe my overheating problem may be related to the PO using Bars stopleak in the system and now that crap is all over in there. I think it's plugged up the heater core and probably the radiator to an extent also.

From reading several other JF threads on cooling, overheating and stopleak, I'm planning on flushing out the system as best I can. Thanks to all those other posts I'm greatly more informed on the process. Once that is done, I'm changing over to an open cooling system with a radiator for the 91+ year XJs. I've already ordered a 2 row radiator, t-stat, hoses and also the heater valve for the newer style cooling system. My WP looks fairly new so I'm skipping that replacement for now. Also, I decided against the updated t-stat housing and plan to operate the e-fan with a switch so I'll eliminate that sensor.

Now for the questions on the flushing in my situation.

Since I have a closed system now, I'm trying to figure out the best way to accomplish the flush before all the new parts go on. It appears the radiator has a leak in one of the end tanks already. This may be why there was stopleak in the system. I'd like to flush the system with the old radiator in place, rather than circulate any of the stopleak crud through my new radiator. Should that be a problem?

There is a T fitting inline in the heater hoses but I don't think it is the part for flushing with a garden hose because the threads are on the outside (opposite). I'm guessing it is just for bleeding/burping air. With the closed system, I'm hoping I can use this as a fresh fluid/water input. But I'll have to adapt it or maybe just try to find the correct T fitting.

Another problem I have is that I'm out in the sticks and only have well water. This well water is very hard and even filtering it, particulates still get through. Is it risky to push that kind of water through the cooling system, even if most of it will come back out again? I can get some gallons of water from the city, but then I won't have the advantage of it being under pressure like from the garden hose to force gunk out.

Finally since I believe my heater core is plugged up too, I was thinking to swap the heater hoses running to the heater core, thus forcing coolant/water in the opposite direction through the core, hopefully dislodging more caked up crud. Is there any reason reversing the flow would be a problem?

Once the flushing part is done, I'll install the new radiator and other parts so hopefully there won't be much stopleak crud remaining. Then I'll have to figure out where to mount the other style overflow tank...

Thoughts on any of the above would be helpful. I'd like to get started this weekend as my radiator should get here on Friday.

Thanks all who contribute to JF!

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post #2 of 33 Old 06-21-2017, 11:08 PM
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I have the later open system but my flush procedure is:

Open the lower rad hose and drain the rad.
Unplug the upper rad hose, stick the garden hose in and run it until it comes out clear.
Refill with prestone/store brand chem flush and hose water and reassemble.
Idle up to temp and 10-30 min after with heater on full blast
Repeat rad flush above
Refill with distilled water and second bottle or second half of bottle of chem flush
Repeat idle procedure and empty rad
Refill with undilutrd coolant to half capacity, and distilled water to make up the rest.

Seems to work for me.

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post #3 of 33 Old 06-22-2017, 06:30 AM
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I had this problem. I did replace the heater core. You can blow through one of the heater core hoses to purge it. Depends on how plugged up it is. Also, there is a drain plug in the block. It don't come out easy the first time. It is a 5/16 or 8mm square drive. Some say they have or heard of some breaking the block taking it out. I have done two and one MB240d successfully. I would replace the water pump and flush out from that opening too.
The hard well water will be OK for a flush. I would get some distilled water for the final flush and to dilute the antifreeze. I use Zerex ZO-5.
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post #4 of 33 Old 06-22-2017, 08:38 AM
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don't put a heater valve back in. Use the 97 and later heater hoses.

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post #5 of 33 Old 06-22-2017, 05:17 PM Thread Starter
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Quote:
Originally Posted by 75SV1 View Post
You can blow through one of the heater core hoses to purge it. Depends on how plugged up it is.
Ok, but any thought on reversing the flow of coolant through the core as a means to flush out more debris? I'd like to avoid replacing the heater core if possible as I imagine it's a PITA.

Quote:
Originally Posted by 75SV1 View Post
Also, there is a drain plug in the block. It don't come out easy the first time. It is a 5/16 or 8mm square drive. Some say they have or heard of some breaking the block taking it out.
I was going to avoid the block drain plug based on the stories I read about breaking or stripping it as well as the 'special' tooling needed. For now I'll plan on backing the rear tires up on ramps to help more coolant flow out the lower rad hose.

Quote:
Originally Posted by 75SV1 View Post
I would get some distilled water for the final flush and to dilute the antifreeze. I use Zerex ZO-5.
Yep, already have that lined up for the job.

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Originally Posted by cruiser54 View Post
don't put a heater valve back in. Use the 97 and later heater hoses.
I did already get a heater valve based on the other forum posts on the open system conversion. Can you explain this a little more or point me to the information on the 97 heater hoses? Is there not a valve on that year XJs?
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post #6 of 33 Old 06-22-2017, 07:00 PM
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The HCV is totally unnecessary and is a weak spot in the cooling system as when it explodes, the coolant loss is tremendous and brings you to a stop.

Thanks to djb383 for this:

One thing you may want to consider is removing/eliminating the heater control valve, if you haven't already. '96 down have the HCV, '97 up the Factory eliminated it.

During the warm months, with a HCV, (temp lever/knob never moved off cold) coolant sits and stagnates inside the heater core.....There's no fresh coolant/corrosion protection circulation through the heater core.

With the HCV removed/eliminated, coolant/corrosion protection flows through the heater core constantly when the motor is running, regardless of where the temp lever/knob is set.

Also, you don't have to remember to turn/slide the heat lever/knob when flushing/re-filling the cooling system because coolant is flowing to/through the heater core when the motor is running and the HCV is absent.

Be sure to plug/cap the small vacuum hose when eliminating the HCV.


HCV Removal



The heat is controlled by the blend air door. I've eliminated at least 10 of them here in Arizona and my AC always works perfectly.

Actual field experience has proven time and time again, by numerous different people, that there is NO downside to eliminating the HCV..

It flat works. Period.

The other benefits are keeping coolant flowing versus being stagnant in the heater core and the dangers/disastrous results of having a valve fail unexpectedly whether you're poking around the engine bay or driving down the highway or trail.

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post #7 of 33 Old 06-23-2017, 06:41 AM
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With the Stop leak in there, I do recommend replacing the water pump. I'd replace it anyways. Then flush the block from that opening. Put the water hose in there and blast ways. As for a reverse flush, I don't know. I would say it wouldn't cause any problems.
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post #8 of 33 Old 06-23-2017, 08:06 AM
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Quote:
Originally Posted by 75SV1 View Post
With the Stop leak in there, I do recommend replacing the water pump. I'd replace it anyways. Then flush the block from that opening. Put the water hose in there and blast ways. As for a reverse flush, I don't know. I would say it wouldn't cause any problems.
Great idea. and you can spray into the block right at the block drain level getting more crap out.

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post #9 of 33 Old 06-23-2017, 09:29 AM Thread Starter
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Quote:
Originally Posted by cruiser54 View Post
The HCV is totally unnecessary and is a weak spot in the cooling system as when it explodes, the coolant loss is tremendous and brings you to a stop.
If it simplifies the system and makes it more reliable, I'm all for it. Thanks for this tip!



Quote:
Originally Posted by cruiser54 View Post
The heat is controlled by the blend air door. I've eliminated at least 10 of them here in Arizona and my AC always works perfectly.

Actual field experience has proven time and time again, by numerous different people, that there is NO downside to eliminating the HCV..

It flat works. Period.
I should have know/thought of this. The Volvos I own have no sort of heater control valve and regulate cab temperature via a blend door also. I've never had any trouble with them so why did AMC or whoever decide this part was necessary? The Volvos also use a closed cooling system that has been very reliable.

Quote:
Originally Posted by 75SV1 View Post
With the Stop leak in there, I do recommend replacing the water pump. I'd replace it anyways. Then flush the block from that opening. Put the water hose in there and blast ways. As for a reverse flush, I don't know. I would say it wouldn't cause any problems.
Ok, you've convinced me. I'll need to source a WP and gasket, but it looks like I'll have more time now since my new radiator showed up but was damaged in shipping....

1989 stock 2 door LTD XJ w/ 4.0L + AW4
and 4 Volvo 240s
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post #10 of 33 Old 06-23-2017, 09:44 AM
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Quote:
Originally Posted by al_xv View Post
I should have know/thought of this. The Volvos I own have no sort of heater control valve and regulate cab temperature via a blend door also. I've never had any trouble with them so why did AMC or whoever decide this part was necessary? The Volvos also use a closed cooling system that has been very reliable.
AMC did a lot of things in vehicles that are pointlessly complicated to chase some kind of minor benefit, like the HCV and the vacuum disconnect front axle in early XJ's. They all get eliminated in the later models for a reason.

Quote:
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Ok, you've convinced me. I'll need to source a WP and gasket, but it looks like I'll have more time now since my new radiator showed up but was damaged in shipping....
If it's of any help, I used a NAPA gold water pump 2.5-3 years ago and it's holding up well. Seems to keep up with the extra requirement of the new 2-row rad as well, though I haven't fully tested that because I was out of town all week and need to address an issue with the fan shroud anyway (damaged during removal/install and now gets into the fan when i get on the gas hard).

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post #11 of 33 Old 06-23-2017, 11:38 AM
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I've had mostly good luck with NAPA WPs too. Might have had one go bad, but I think I had the belt tensioned to tight. Also, other problems in the accessory drive. I would also put the water hose to the hoses that go into the heater core. I did flush the heater core this way on one of mine. Also, as you stated the WP looks new. Then you could go with just a gasket. Still, I think a WP is like $20-$30. If your not in AZ or Middle East etc. I don't think you need a Flowcooler.
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post #12 of 33 Old 06-23-2017, 12:01 PM
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I'm not so sure about the flowcooler anyway. Most of the good reviews I read on flowcooler and such it's done as part of a huge overhaul anyway, and then they rave about the pump. Reported results are a lot spottier when it's just the pump and all other things held even, even a few people saying it did worse.

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post #13 of 33 Old 06-23-2017, 04:49 PM Thread Starter
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Quote:
Originally Posted by 75SV1 View Post
Also, as you stated the WP looks new. Then you could go with just a gasket. Still, I think a WP is like $20-$30.
Quote:
Originally Posted by bluejunior View Post
If it's of any help, I used a NAPA gold water pump 2.5-3 years ago and it's holding up well.
Thanks bulejnior and 75SV1. I ran down to Napa and checked on prices. WP was about $37 and tax for the NEW napa WP (I don't trust reman parts at all), the gasket only $2 but didn't have it in stock. I've got the gasket ordered and will decide on the WP once I pull the current one off. I appreciate the input!

Quote:
Originally Posted by 75SV1 View Post
I would also put the water hose to the hoses that go into the heater core. I did flush the heater core this way on one of mine.
I was planning on draining the old coolant then filling with water and running the engine up to temp. Drain and then pull WP and hoses to spray the hose in the core and WP opening and anywhere else I have access. Reassemble, more water, drain and then install the new rad/cap/t-stat and hoses and fill with proper 50/50 mix. I'm a little leery of putting the chemical coolant system cleaner through but might try a little vinegar in one of the cycles.

Again, thanks for all the info. I haven't ever had to clean out a cooling system like gunked up like this before so I must take all the advice I can get.

Also, cruiser, if you want any photos for your article on your website, just let me know. I've read through a bunch of your articles and found much of that information helpful as well as your posts here on JF.

1989 stock 2 door LTD XJ w/ 4.0L + AW4
and 4 Volvo 240s
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post #14 of 33 Old 07-11-2017, 01:23 PM Thread Starter
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I wrapped up this project on Saturday. The direct heater core hoses sure cleans up the engine bay and makes it simple.

I got about 3 good flushes through the block and had some deposits come out, but less than expected. Back flushing the heater core produced a good amount of crud,so that was worth it. I did end up swapping the two hoses for the heater core at the t-stat and WP for the flushes when the engine was run. After pulling the t-stat and WP, the inside of block and head were fairly clear of and deposits. The WP looked good so I just re-installed, and honestly the thermostat looked good, but I already had a new one, so put that in. Besides the PO had done a poor job on the housing gasket and got RTV everywhere on the t-stat housing.

It sat for a good week+ with just a small amount of water in the block and that created new rust. Before I filled with coolant, I ran a few gallons of distilled through until I got clear water coming out the lower WP. When I did this, I didn't have the radiator in the loop to prevent rusty particulates finding a new home in the new 2 row radiator. Once I had clear water coming out again, I put on the last hoses and added straight coolant and more distilled.

I repositioned it to have the front wheels up on ramps and kept the rad cap off to clear out any remaining air. Topped it up and added some more to the overflow tank and initial tests were good. I idled it for about 20 minutes and waited for the tstat to open. Gauge never went over the 210 mark. I then went for a test drive on a 4wd trail a few mile away for about 30 minutes. Did some steep incline climbs at low speed and temps were still under the 210 mark.

Sunday I went for a longer test drive. It was an hour journey each way. The last time I did this round trip I had to stop and cool down twice on the way and once on the return trip. This time temps were not hitting the red zone and overall temps were within range. However at one point the gauge started heading past the 210 mark to somewhere in the range of 225-230. I had stopped to open a gate. When I got out of the jeep, the gauge was right at 210-215. When I got through the gate and started the final leg of my trip, temps hit the highest around 225-230. Once I got moving again temps went back down and finally back in the 210 range. Not sure if elevation is playing any part but this trip starts at around 6000ft elevation and ended just short of 9000ft. The gate where temps hit the high was about 8500ft. On the return trip temps were below 210 the whole drive.

Finally, the electric fan was not operational on this drive. As I understand it from reading several other posts on overheating, the electric fan shouldn't be necessary unless using AC or towing. Since I wasn't towing and just removed the AC system, I expected I shouldn't need the electric fan to stay in the normal range. I'll be setting up a manual switch on that soon, but for now it's just disconnected.

Is this temp spike evidence of further issues? At this point probably 90% of the cooling system has been cleaned and updated. My only guess is the fan clutch is shot.

1989 stock 2 door LTD XJ w/ 4.0L + AW4
and 4 Volvo 240s
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post #15 of 33 Old 07-12-2017, 08:20 AM
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The electric fan should come on at about 218* to help with cooling.

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