overheating problems

[Ecomike]

What kind of mechanical fan???

Your down to the mechanical fan or radiator (partially clogged) at this point.

Ok I replaced the t-stat and temporarily straight wired the electric fan it did a lot better than before. The only time it tried to overheat was sitting and letting it idle while waiting in line to pick the kids up from school. That's the only time it got past 210 F and it went up to probably 235 F the mechanical fan pulls full all the time ( no clutch ) and the electric fan as well so now what? Any other ideas it's also now 50/50 anti-freeze.

 

[AZRockRunner]

Also, check the lower hose and make sure it is not collapsing. Most of the aftermarket ones dont have the spring in them and collapse under heat and pressure. Getting one for a 91 from the dealer fits perfect and prevents that problem.

 

[pauldo39]

Also, check the lower hose and make sure it is not collapsing. Most of the aftermarket ones dont have the spring in them and collapse under heat and pressure. Getting one for a 91 from the dealer fits perfect and prevents that problem.

Yes, but he is overheating when idling. RKbonds, I assume you are able to cruise on the highway without any problems? The higher RPMs when on the highway (or doing anything but idling) are the only times there is a slight chance your lower hose is collapsing. Just gun the throttle with the hood open and look at the hose. I had a non-spring hose in there for awhile and even with the rpms up to 4000 or so, the hose squeezed itself an almost unnoticeable amount, and this was with a 14 year old clogged as hell radiator (which I subsequently replaced :spin1: ). I did eventually put the dealership one back on with a spring after I got my new radiator, but not before I had gone for a long, strenuous drive and I had no problems.

So, bottom line, I highly doubt your hose is your problem, BUT the dealership hoses are of a higher quality and can give peace of mind.

Now, onwards. As stated above, if you aren't overheating at high speeds, your radiator is almost certainly not the problem, although it is not unheard of for one to go bad in a very short period of time, especially if the block has a lot of junk in it when the switch is made. This leaves 2, or I guess more like 3 options.

#1: Water pump: I know you said it is new, but trust me, I had a period where I went through more water pumps in less time than I thought was physically possible. If the impellers are eroded or damaged (especially if only water and no antifreeze was used for awhile), they won't do much when idling but when moving fast enough may provide enough flow when not idling.

#2 (and 3): Airflow. I know this sounds obvious, but make sure the path of air from outside the grille to through the radiator is completely unobstructed. Get a fin comb or icepick or tiny screwdriver and straighten condenser fins, radiator fins, degrease everything and hose out, clean crap out from on the radiator supports, etc. I did that once a few years ago and it made a huge difference. If your mech. fan is locked and your e-fan is always on, I'm at a bit of a loss there, because you can't get much more airflow than that, at least with the stock fans. But the huge majority of slow moving overheating problems have to do with a lack of airflow over the radiator.

I'm in the process of getting ready for putting in a fan from a Lincoln Mark VIII to replace the mech fan. My clutch is bad again and locking up the blades worries me when those blades aren't rated for high rpms. Cheap clutches are a crap shoot, and good ones or ones from the dealer are well over $100. I know many have gone with the elec fan approach to solve low speed problems, but when I get my fan I plan on giving a full write up/pics for anyone who is interested.

The right thermostat will keep the flow in check, like others have said.

 

[Ecomike]

I replaced my fan clutch with a non-oem, aftermarket clutch over 3 years ago for about $45 and it has worked flawlessly. The key is to buy the better quality after market clutch that has the flat coil spring on the front side of the clutch!

 

[90xj06]

i have a 90. and mine never gets past the first dash in the temp gauge. so i think thats around 195 ish or something. but this is all factory cooling except for the 3 row instead of 2 row radiator. if you get a small air pocket where the temp sensor is for the gauge it will give false readings. with the engine cold. loosen the sensor to the point where its just about to come out. and if no coolant comes out you have air in there. just leave it out until coolant comes out and screw it back in. next step is to check that the coolant bottle is working working. and the coolant bottle cap.

 

[Ecomike]

Actually the first dash is right at 165 F, and the second dash is right at 190 F. The gauge is very non-linear.

Based on his last test I suspect a slightly clogged radiator or Mechanical fan problem since it cools fine everywhere but long idles now.

What is your idle speed in park and drive?

i have a 90. and mine never gets past the first dash in the temp gauge. so i think thats around 195 ish or something. but this is all factory cooling except for the 3 row instead of 2 row radiator. if you get a small air pocket where the temp sensor is for the gauge it will give false readings. with the engine cold. loosen the sensor to the point where its just about to come out. and if no coolant comes out you have air in there. just leave it out until coolant comes out and screw it back in. next step is to check that the coolant bottle is working working. and the coolant bottle cap.

 

[rkbonds]

Idle speed in park is 6oo rpm's I don't remember what it is in drive i'll have to check.

 

[rkbonds]

Ok today I ran it with the ac off the whole time and didn't have any trouble with the overheating. I guess this means I just need to leave the ac off and enjoy the heat. lol my jeep doesn't like me:banghead:

 

[Ecomike]

Idle speed in park is 6oo rpm's I don't remember what it is in drive i'll have to check.

600 rpm in park is a bit low. It should be 750 in park and about 600 in drive at idle. That could affect air flow at idle with the AC on.

Have you considered just turning the AC off at stop lights or slow heavy traffic. You could also try different AC settings, like a lower fan speed to lower the AC heat load under the hood. Lastly, make sure you have the AC on Max AC and not normal AC. Normal AC draws in hot outdoor air and tripples the heat load under the hood! Max AC recirculates the cooler dryer air in the cab.

Also might want to check that AC Max setting duct damper is working. Mine was in Normal mode even though I had Max AC selected because the air (vacuum) valve that closes the normally open, make up, outdoor air damper door was bad. The damper door and valve is near the floor and passenger door under the dash. Easy to check and see what it is doing.

You never explained what you meant by locked mechanical fan. Is there no clutch on yours? Is it a flex fan, or what?

Lastly, a slightly clogged radiator will first show up at idle with AC running.

You might consider a mild acid (sulfamic acid formula based coolant flush) radiator and block cleaner to see if you can restore some extra flow through that radiator before it gets worse!

 

[rkbonds]

The rpm's are actually the same in park and in drive. The mechanical fan is locked up meaning, the clutch no longer works it's locked tight I can't turn it by hand. So there for it is turning at engine speed.

The radiator has been gone through and rodded out and flushed and only used on this motor since the motor change so I don't think that's the problem. Last night I pulled the t-stat and drilled it and that seems to be helping I think. The temp stayed lower today but then again no long time idle. I'm getting closer to solving the problem I hope.

I'll have to check the ac I know I run it on max but, as you said it might not be working properly.

 

[rkbonds]

I think it might be the water pump because I can watch the temp creep up and then I can give it some gas and get the rpm's up to 1000 or a little over and I can watch the temp ease back down some ( this is in park of course ). Either way I do have it managable for the time being until I can save some more money to do more work on it. Unless someone has a water pump they want to donate. lol

 

[AZRockRunner]

Dont have a water pump to donate, but I HIGHLY recommend the HESCO high flow unit. I can rock crawl in the 110 degree heat and no problems at all. And thats with a single core non HD radiator.
They are a bit spendy at 120 buckaroonies but well worth it in my opinion.

 

[Ecomike]

Something is not right if the idle is unchanged between park and drive! The tranny should load down the engine about 100 rpm in drive, at idle, compared to park at idle.

Rodding out a radiator does open up the blocked tubes so water can flow improving the cooling system, but it does not adequitely clean the scale (silicate, carbonate, calcium..... scale) off the tube walls that acts like insulation. A one mill thick layer of scale on the tube walls can reduce the peak heat transfer rate (capacity of the radiator) a bunch, like 20% easy, which in a marginal system operating at the margins of the system design can result in runaway, or near runaway temperatures.

A good acid descaler, with sulfamic acid in the formula can disolve the remaining insulating scale of the tube walls that a rodding out does not quite reach. Also, note, that descaler does NOT rod out the tubes, if a tube is sealed off with scale the chemical descaler will not open the tube back up, so it is best to do both, rod it out first, then descale it chemcially.

If you have not already done it, or if the rad shop did not do it for you, I would run a batch of descaler in it for a good hour at idle, then drain, flush and refill it before I went to the trouble of replacing the water pump. For that matter a high flow thermostat would accomplish increased coolant flow with the old water pump for a lot less dollars and lot a lot less effort.

The rpm's are actually the same in park and in drive. The mechanical fan is locked up meaning, the clutch no longer works it's locked tight I can't turn it by hand. So there for it is turning at engine speed.

The radiator has been gone through and rodded out and flushed and only used on this motor since the motor change so I don't think that's the problem. Last night I pulled the t-stat and drilled it and that seems to be helping I think. The temp stayed lower today but then again no long time idle. I'm getting closer to solving the problem I hope.

I'll have to check the ac I know I run it on max but, as you said it might not be working properly.

 

[heyhar]

Four years ago, I needed to replace the lifters in my '92, so off came the head. While it was off, I took the time to basically clean out every nook and cranny I could reach a file or Dremel attachment into. The coolant passage at the rear of the head was rather clogged, moreso than any other visible part of the system. It never had an overheating problem before, but after I removed as much of the build-up as I could, it ran even cooler. Also, the dealer seems to be the only place to get the proper t-stat, the one with the little check-ball in it, which I read here somewhere aids in burping the system, not only at servicing, but continuously. I know that yanking the head to scrape out scum is a little severe, but if all the other options are exhausted, it may be a last-ditch solution. Good luck!

 

[pauldo39]

I'm not sure if I agree about the statement that "a slightly clogged radiator will first manifest itself idling with a/c on," especially based on experience. I've dealt with overheating on 2 different jeeps, the last one I fought for years before replacing the radiator. Even with a balanced design thermostat at 180 (a long time ago when I was troubleshooting), if I started up the jeep in 100 degree weather and left it idling for an hour the temp would NEVER budge above 180, but the second I took to the highway the temp would start to go and could not recover unless I shut it off. Now I've seen stranger things, and I'm certainly not saying that your radiator is perfectly fine, BUT I do think the water pump is a more likely alternative. You could try the higher flow tstat/tstat housing but that is more like a compensation for a bad water pump, and if you ever replace the w/p you may find yourself having too high of a flow resulting in overheating again.

 

[pauldo39]

And I should mention that I use a basic OEM water pump (30-50 bucks anywhere, NEW not reman) and my jeep's temp never budges no matter what I do.

 

[rkbonds]

I went today and purchased some good radiator cleaner that I'll be working in over the weekend. I thought they had done all this at the radiator shop but, it's worth trying again before I replace the water pump.

 

[pauldo39]

Make sure you use the 6 hour flushes instead of one of the 10-15 minute ones. I've had really bad experiences with the quick ones, as they tend to damage water pump seals, but running 2 bottles of the 6 hour flush with the rest water for a couple days really brings out some crap. It won't do much to unplug a clog in your radiator, but if anything it will dissolve some of the crap in the block/head and make sure if you do get another radiator your system will be fresh for it, i.e. it won't get contaminated right away from the rest of the system.

 

[rkbonds]

That's actually what I purchased and it says I can use it over a couple of days so I'm tryin it out now and I'll change it Saturday.

 

[badron]

I would power flush the heater core. Disconnect both the supply and return . Attach a house to one line and flush until drainage runs clear. switch lines and flush again.
(IMO) Flushing is to keep the coolant system clear. Ones they have clogged flushing seldom helps. I quit flushing an over heating engine to clear the rad a long time ago. I flush to clean the block and then replace the rad/heater. If one clogs the other is well on it's way to getting that way in most cases.
But it will not hurt to try, luck