Rust colored engine coolant - Overheating???

I'm looking for any tips or solutions for an overheating issue...What I've been troubleshooting for the past year or so is a stubborn overheating issue. The first time I overheated was last year climbing over Monarch Pass, near Gunnison, Colorado. By the time I reached the summit I was badly overheating. The color of the coolant was that of RUST. Since that incident, I have had continued problems. I have replaced the radiator, thermostat, all cooling hoses, heater core and water pump (4.0L. with 140,000 miles) The coolant color still looks like rust after about 2 months. So it seems as though I have a rusted engine block at the very least, but has anyone had a similar experience and if so what did you do to remedy the problem? Is replacing the block the next step? I've already tried coolant flushing products, regular visits to the shop to have the block fully flushed, but without fail, the coolant is back to rust colored and I'm close to overheating again.

This is my first time using a forum online, I hope that there is someone out there with some advice...

Thanx
Milehilonewolf

my problem

every some odd months the color of my coolant in my tank turns a redish brown color. everytime i take my coolant tank out and flush it with beach and water and it gets it clean. i think the cause of this problem is the fact we live in az and all the dusy and mud and trail dirt, try doing that, and also take a pressure washer to the front of ur jeep on the radiator and see what color water comes out, it will probably be a dirt colored water just like mine was, and then that will help with the colored water most likely, and on top of that empty the tank and do that and that should help alot. the fins are prob dirty on the radiator and that helped my jeep cool down alot. also if u have a electric secondary fan that is ran to a temp sensor u could tap into that and make it run off a switch and make it so u can turn it on right away instead of when the temp thinks it needs it, i also did this. if any of this helps please let me know and PM me so i get the response faster, thanks

Excuse my ignorance, but being that this is the first time I've used an online forum I don't know what you mean by "PM" in regards to contacting you quicker...what does PM stand for?

I thank you for your suggestion...I will be at my father's shop within the next couple weeks to install a new exhaust system and we are going to flush the engine at that time. I will try what you said about cleaning out the coolant tank...hopefully that helps keep the coolant clean for longer period of time.

Thanx
Milehilonewolf

PM=Private Message, if you click the name of the person on the forum a menu drops down, click private message and you're set

Thanks for the info on "Private Messaging"...I've only been on this forum an hour and feel as though I might be spending many more hours on here in the future....it seems like there is a wealth of information to be found here...Thanks again

Milehilonewolf

For the overheating problem: Is the aux. cooling fan running when it should? The fan should come on when the AC is on, or when the engine temp hits like 206 deg.(I think) If the fan isn't running, that may explain the intermittent overheating problem.

milehilonewolf said:

I'm looking for any tips or solutions for an overheating issue...What I've been troubleshooting for the past year or so is a stubborn overheating issue. The first time I overheated was last year climbing over Monarch Pass, near Gunnison, Colorado. By the time I reached the summit I was badly overheating. The color of the coolant was that of RUST. Since that incident, I have had continued problems. I have replaced the radiator, thermostat, all cooling hoses, heater core and water pump (4.0L. with 140,000 miles) The coolant color still looks like rust after about 2 months. So it seems as though I have a rusted engine block at the very least, but has anyone had a similar experience and if so what did you do to remedy the problem? Is replacing the block the next step? I've already tried coolant flushing products, regular visits to the shop to have the block fully flushed, but without fail, the coolant is back to rust colored and I'm close to overheating again.

This is my first time using a forum online, I hope that there is someone out there with some advice...

Thanx
Milehilonewolf

Click to expand...

What is the year of your XJ?

Do check to see if your auxiliary electric fan is working, however if your air conditioning is off, the fan should not turn itself on until the coolant temp reaches around 220 degrees and shouldn't turn off again until the temp reaches 200. If you have the a/c on, the fan should cycle on and off with the a/c compressor. Check to make sure this is functioning (although I do realize this has little to do with your coolant).

Have you checked the head gasket for leaks? It isn't a definitive method for checking but if you have a milky, whitish residue on the oil cap you could be leaking antifreeze into your oil and vice versa... oil leaking into the coolant would tint it, however it would seem as though you would need a substantial leak in order to turn all of the coolant brown. Other classic head gasket symptoms would be white exhaust (with a sweetish smell) and/or constant air bubbles in the coolant due to engine exhaust gases) Worth a look.

With all the flushing you have been doing, it would seem as though you would be at least removing the majority of the loose rust in the block, or at least enough to slow the process of the color change. I remember the first time I took my jeep into the shop when I was probably only 17 or 18 years old and asked for a coolant flush (thinking they would hook it up to a machine) and all they did was drain and fill it. I was so disgusted, that didn't do ANYTHING to clean stuff out.

I couldn't tell from your first post, but if you have only used the 15 minute idle/drain flushes, I would try using the 6 hour flushes (or 2+ at the same time). You drain out all your coolant, dump the flushes in with water, and run the car normally for about 6-8 hours worth of driving. These probably won't unclog a restriction, but will dissolve a lot of rust.

Make sure you COMPLETELY drain out the flush when done, and refill with the proper 50/50 mixture of water/antifreeze (USING DISTILLED WATER OR A PREMIX ONLY, NO TAP WATER!!!!). Again, maybe you have possibly already done this procedure, but worth mentioning.

Let us know if you've tried any of the above, if not it's worth a shot, if you have we'll try some other suggestions.

Crap, and I should add it would really help to fill us in with some more details about your overheating. Does it overheat in the city/idling, on the highway, or both? (or randomly?). If it overheats in the city/idling and does fine on the highway, your fan clutch/e-fan probably aren't functioning properly. It could also be a bad, eroded water pump but I see you recently replaced that. If it overheats more on the highway, unfortunately your chances are better that your relatively new radiator is clogged and can't keep up. Does turning on the heat stop the overheating, or at least slow it down? Also make sure that the exterior of the radiator is free from dirt, bugs, grass, whatever. Spray some degreaser on there, let it soak, then hose it out. Also use a fin comb or another very thin tool to straighten bent fins. I know you mention a new radiator, but that wouldn't be the first time a new radiator was bad.

New 16# pressure cap???

Can you tell I've been through this same problem before (well, not the rusty coolant..)?

Yes, the aux. fan runs almost constantly when the AC is on, and Yes, the fan comes on with the AC off and an engine temp around 215-220 or so. When I run the AC the temp stays steady around 230, compared to a normal operating temp of 210. When traveling in the mountains, with the temp around 220 or so, all it takes is one long grade with a couple of transmission kick downs to push the temp into the 240+ range....sorry to say, but for the last year I have avoided any mountain travel.

I had a local mechanic suggest that the fan clutch assembly might be malfunctioning, but after the engine is warm there seems to be proper tension on the fan???

I have tried a variation of the 6 hour flush you mentioned, but I have not done one to the extent you mentioned. What I think I may do is attempt your flush method since I have the time this go around to do so.

My jeep is a 1998 with a 4.0L with 140,000 miles.

I edited my post while you were posting your response, take a look at the last paragraph.

the color of the coolant in my xj was that of rust when i first bought it. i had a number of cooling system issues including a thermostat stuck open, a faulty water pump and some crumbling hoses.

the first thing i did and probably the easiest was a modified flush. i completely drained the cooling system and flushed it myself. an easy way is to be sure to turn the heater all the way on full blast to open up the heater core to ensure a complete flush. take the heater hoses off from the water pump as well as the radiator hoses (i left the lower radiator hose hooked to the rad to help direct the water coming out of the rad). i took a regular garden hose and put it to each of the hoses and the rad cap. keep going back and forth alternating the flow of water through the heater core. a lot of gunk builds up in there and the only way to get most of it out is to flush in both directions with the heater set to on (engine off of course while doing all of this) repeat the process with the rad and also the water pump. the coolant reservoir will come out so it would be a good idea to remove that and rinse it out or even fill with soapy water and shake it to help dislodge a lot of crud. do your best to get all the water out to keep a proper solution (good habit to do)

if you dont to too much driving you can add 1 galon of distilled vinegar and fill to full with water. this is best to be done in spring or fall. if conditions require coolant/antifreeze then fill with 1 gallon of distilled vinegar and fill to full with coolant full strength. the vinegar helps to remove the rust and water deposits inside the cooling system. I ran mine like that for about a month with occasional use. i would periotically turn on the heater to make sure to get the vinegar solution to flow through the heater core.

next, drain and repeat the the flush process. once you think its good and clean, keep going. you want to be running clean water through it with no deposits removing for a few minutes. this makes it more likely that most of the crud is out. dont be alarmed that the vinegar solution will be an ugly color. its normal for this proceedure. its all the crud that is being removed from the inside of your engine. complete the flush and make sure you get all the water out that you can.

fill with propper solution of coolant and distilled water. i use the 50/50 solution just for simplicity. keep an eye on your coolant level, coolant color and look for leaks in the cooling system. removing the crud may uncover some leaks in hoses, seals or gaskets.

thermostats are not to expensive so i would recomend replacing with a new one everytime you add your coolant solution after a flush. just good insurance.

i didnt get all the water out after i flushed my system. the following winter i froze my cooling system and fried my water pump. good excuse to get a new one and drain fill with proper solution.

i was amazed with how much crud was removed by the vinegar solution. i was glad to get all that crud out. remember, a lot of junk lingers, settles and solidifies in the heater core. flushing that out is crutial for a complete flush. plus your heater may work more efficiently the next winter depending how clogged it was.

hope that helps

The overheating ONLY occurs while at highway speeds, never at idle. Turning on the Heater drops the temp considerably...on my trip to Ouray last summer I had to drive with the heater on full blast for 4 hours straight on the way back to denver (90 degree day) just to keep the temp reasonable...me and my lady were showing signs of heat stroke near the end of that trip

Radiator cap was replaced with radiator. Radiator is nothing special, just a OEM replacement. Maybe I should replace it again, but is there a higher quality brand to look into next time??

Speaking of my lady...it seems I have been summoned to turn in for the night..I will check back tomorrow on the posts...I sincerely appreciate the time you all have given to my problem so far...

...to be continued
Milehilonewolf

The lower radiator hose has a spring in it that is known to rust away... Try replacing, as it probably needs doing anyway. Replace your thermostat.

make sure the radiator cap is rated for the max of the radiator specified pressure. it should be 16psi from the factory. MOST replacement caps at the parts stores are 13psi. the only parts store that i've found that was able to get me a 16psi cap was at napa.

you can test your fan clutch by locking the clutch. i posted that here
http://www.naxja.org/forum/showthread.php?t=923165&page=2&highlight=clutch

also it could be something as simple as a loose belt, or possibly even a bad sending unit reading higher than it actually is. the only way to verify that would be to hook up a scan tool and monitor the coolant temp sensor through the pcm (pcm and gauge use 2 different sensors).

it could also be a cracked/leaking radiator. it's insanely common on jeep wranglers to overheat on the highway but not in the city due to a defective radiator. that happened to my wife. never had a problem in town and then drove 3 hours away on the highway during the night. the next day coming home during slightly warmer temps, she couldn't drive more than 15-20 minutes at a time without overheating. it ended up being a cracked radiator.

it could also be your transmission. if you have an automatic, and for some reason your transmission is getting insanely hot, the tranny fluid will actually heat up the coolant as it passes through the radiator (tranny fluid and coolant share the radiator). i've had that happen on my cherokee while wheeling to hard. i overheated my engine by frying my transmission. but that is a somewhat extreme situation. but if you absolutely can't find any other problems, it's something to keep in mind.

the thermostat and thermostat gasket is cheap enough to change it out on a regular basis just to make sure it's working properly. specially since the parts store ones are really cheap quality. personally i replace my thermostat EVERY year.

it could also be that you have high corrosion inside your radiator which would clogg up the passages now allowing the coolant to flow and efficient and transfer the heat as efficient which would make it move through dropping the temperature much.

hope those give you some ideas to look at.

I think your problem lies in a poor radiator. The fact that it overheats only on the highway, coupled with the fact that the heat brings it down (heater acts like another mini radiator for the coolant), points to your radiator. It may very well have been a faulty manufacture, already rusted on the inside (especially if aluminum!).

While their is no definitive test, let me tell you the road I went down. I was overheating on the highway and replaced water pumps, went through tons of thermostats of varying degrees, all kinds of coolant additives, transmission treatments, leaving e-fan on always, locking the fan clutch, 80/20 water/coolant mix... well, it was the dumbest money I ever spent. I bought a new radiator, no more problems.

I (along with many others on this forum) purchased an all metal 3 row CSF radiator from "www.radiatorbarn.com". They will ship this radiator to your door for $170, and installs in a few hours max, not difficult at all. If you do decide to go this route, I recommend going to the dealership to pick up new upper and lower hoses (lower with the internal spring) and a dealership thermostat. Take the thermostat/tstat housing off after you have removed the old radiator, and blast out the block with a pressure washer to get remaining stuff out. You want the rest of the coolant passages clean before you stick a brand new radiator in there.

Again, I will not guarantee this is your problem, but overheating on the highway only is a pretty good indication of radiator failure.