Overheating problem-need help!

[alaskan-xplorer]

Hi all-a question about overheating in my stock 93 xplorer. Slightly long, so please bear with me. A few days ago I noticed that the truck seemed to be getting hotter than it normally should have for a short drive. Was going to have a look at it over the weekend. Well, I was driving along when the temp gauge suddenly started going haywire and would go all the way to the end of the normal range, nearly overheating. Had a look at the coolant, which had collected in the overflow tank, but there wasn't any in the radiator itself, so the truck wasn't eating the coolant at any rate. Just that all the coolant was collecting in the overflow, and not flowing back into the radiator. Turns out the coolant had a lot of rust in it and the old owner hadn't flushed the system in a while. So I figured that the thermostat was probably gunked up as well. Had the coolant flushed, changed, and the thermostat replaced. Worked well for a day, and then the same thing happened. Took it back in, and it was flushed again. The guy drove it all around and it didn't overheat. Worked well for me for a day and it happened again...its driving me nuts! Spoke to a friend who said he had a similar problem in his truck, only it was an old toyota, where a sensor that was supposed to draw coolant into the radiator was busted. Any ideas on whether it could be anything similar in my truck, or any input on what this might be due to? Thanks for reading this!

 

[410Fortune]

Suspect: radiator cap, air in the system, you are losing coolant, or the fan clutch is toasted.
any leaks under the truck?
I am guessing not since you did not mention them.

There is no sensor that controls the flow of coolant to the overflow tank, only the radiator cap does that. The rad cap is a simple spring, when the coolant heats up it adds pressure to the system, this compresses the spring allowing the additional fluid from the hot conditions to escape into the overflow.

Sounds like your rad cap is bad., a stock cap is 17 psi I believe, I have run 7-8 psi on these Fords to help stop/slow down a leak until it can be repaired.
So no leak = buy a stock psi replacement, slow leak consider lower psi.

Changing the PSI of your radiator cap to a lower rate effectivley lowers the boiling point of your coolant and its not the best but if the rest of the system (waterpump, radiator, hoses, thermostat) are up to par then it will get you by until the leak is resolved.
Larger leaks you should consider a good sealing product, I prefer the BG cooling system stop leak, this stuff is amazing, seriously I was losing CUPS of coolant out the top of my custom radiator.
Its been 4 months or so and it leaks like 2 drops a week.
There are other products but from what I have seen I will stick with BG, the first time I saw it a BG demo guy poked holes in a styrofoam cup with a pencil, poured in water, added a little sealant and BAM leaks stopped.
It hits air, it seals the gap.
External leaks in the system can be easily located with a coolant pressure tester, you can rent from many auto parts places usually free.

The sensor that feeds your dash gage has also been known to go bad, but in your case with the loss of coolant and full overflow I would start by checking my fan for cracks, see if the fan clutch is working (usually they break, they stay on and you will hear the fan roar at all times, not jsut when the underhood temps get hot). An air pocket behind the thermostat can also make a funky temp gage.

You have a new thermostat so lets assume it was installed properly because the same issue was present before the new parts.
You should burp the cooling system and fill it up or flush/fill again, then replace your radiator cap.
Do a visual inspection for coolant leaks, around waterpump, thermostat housing, hoses, rad, heat core, etc.

worst case scenario there is a leaking head gasket/head but you will notice a cooling loss, slow or fast, condensation in the tailpipe, so keep an eye on your coolant level after you burp the system again and get your currant fluctuation issue resolved.

Do not overheat the engine, when you do or if it has been overheated in the past the chances of a bad gasket/cracked head are increased 10 fold.
Many people will try a quick fix (coolant system stop leak) and dump/sell a vehicle when this happens to them



hope that helps!

 

[alaskan-xplorer]

Thanks for the quick reply! Actually, I should have mentioned this in the earlier post-the radiator cap was also changed to one rated at 7 psi. There doesn't seem to be any leaks of coolant from the engine at all, which is why I'm stumped. The truck is not actually losing any coolant. What does happen is that all the coolant collects in the overflow (leaving the radiator empty) and then leaks out from the top of the overflow tank. So I'm guessing that it might be the fan clutch? Thanks again!

 

[ma96782]

All the above is some really good advice.

A simple, "cheap check:"

A radiator shop should be able to test your radiator/system for a leak, w/ a simple pressure test.

The local well stocked auto parts store may have the cap tester and could test your radiator cap.

Did you notice if the anti-freeze was circulating? After you did the thermostat and flush? If NOT, suspect a water pump.

Aloha, Mark

PS.......I don't off hand KNOW what the factory spec is on the radiator cap......but, 7 lbs (sounds low). At any rate, figure if the cap is set too low, the anti-freeze will push (pressurize) on the cap...the cap will release....anti-freeze ends up in the overflow tank.

Course a crack head or block..........releases pressure or boils the anti-freeze........and could do the same.

Fan clutch: My test.......when the engine is cold (and off).....try spinning the fan by hand. Feel the kind of soft resistance....or it may spin freely.....it's acceptable (for me). If it don't spin or if it's really though to get it to go around.........then, suspect the fan clutch.

As for the plastic fan........small cracks in the plastic is one thing........but, you'll have to make the call to replace, or live with it.

 

[410Fortune]

put a 17 psi cap back on, its possible you got a bad cap as well.
The system heating up is whats forcing the fluid into and out of the overflow resevoir
The system could be gettig hot because you have no coolant after driving


Does not sound like the fan clutch
Truck sounds like it is overheating badly, does it heat up every time you drive it?

Your system holds almost 4 gallons of coolant the overflow tank holds like 1/4 of a gallon, so I would fill the system, burp it (very important), then put a 17 psi cap back on, if it still overheats you are likely looking at a bad waterpump, a blocked/non working thermostat or air still in the system

If you do notice a coolant loss while driving over time and no leaks aroudn the system I suspect a head gasket/head issue.
he 91-94 are notorious for this, especially as they get older and especially if they are heated up/overheated.

With that said I drove my V6 with a small head gasket leak for 2 years with the leak still there.

 

[MarksSC94]

There are a couple things that can cause this. 410 addressed one. The radiator cap. The stock cap is 14psi. Don't go larger or you risk blowing a seal or gasket and don't go lower or you risk running out of coolent and causing the coolent to boil when you don't want it to.

The other thing that can cause this is if you have small leak. One way to really confirm this is to pressure check your cooling system. That is done by replacing your radiator cap with a cap that has and air valve and guage on it. The system is pumped to about 13 psi and left there. After a some time, say 20 minutes the pressure is checked. If the pressure has dropped, you have a leak. This is likely.

Don't use leak stops. They are really good at stopping leaks, but if you have limited coolent flow in a water jacket, or in several of the tubes in the radiator, they can also plug it and make the problem worse.

What you can do:

Check out the radiator. Look at the radiator carefully. If you see an area in the cooling fins that is much dirtier looking than the rest, your radiator is probably leaking. Dirt will collect and stick pretty good in that area. If the leak is recent, then it may only look wet. Part of the problem is that when there is a tiny pin hole in the system, it doesn't just squirt out, it will steam out because of the lack of preasure when it hits air and the lack coolent in the system.

Check out the raditor hoses. If any of them is bulged out at all, replace the hose. If it isn't leaking, then it might burst if you repair the leak.

The last thing that is easy for you to check is the water pump. There is a small hole on the neck of the pump. It is called a weep hole. Look into the hole and see if you see any rust in there. If there is rust, then the seal on the pump is going or has gone out and you have lost some coolent from there. The hole is your indicator there is a problem with the pump seal. Sometimes you go months or years like this. But you have to remember there are bearings or bushings in the pump. This about what the hot liquid might be doing to those and add on it to the rust that is added to it from the engine block.

If you can look around with a mirror, there are a several plugs on the engine block. These are freeze plugs. They are designed to pop out if your coolent freezes so that the frozen coolent won't crack the block. It is cheaper to replace 5 dollars in plugs and 10 bucks of coolent and water than to replace the whole engine. The are round and on the sides of and rear of the engine. If you can, and it isn't easy, check them out with a mirror and light and see if any of them have holes, cracks or a bunch of rust built up around one of them it may need to be replaced. They are made of brass, tin, or aluminum and will corrode, but I haven't heard of it happening a quite awhile.

Another thing that can leak is the heater core. The aren't terribly expensive, but they are a PITA to repace. They are like a little raditor under your dash to provide heat when you are cold. They can take several hours and are very expensive to pay someone else to replace because they don't want to do it. I have yet to hear someone say "Hey I love replacing heater cores". Personally I'd rather have a root canal. I think it is easier to replace a lung than it is to replace the heater core. The reason for this is because it is under the dash and usually you have to remove a couple of panals, then tear apart the inside of the dash to access it, then open the climate box it is in, then crawl under or over the engine to undo the 2 hoses it is hooked to then do a bunch of it upside down and on a Tuesday when the moon and Mars are in the alignment with Jupitor.

Last but not least check the oil and tranny fluid. If either is creamy color, then you have bigger problems The tranny has a little cooler in the radiator and it might be leaking coolent into the tranny. if this is the case replace the radiator and install an external cooler for the tranny and have the tranny flushed. If your engine oil is creamy or clumpy looking, then you have some big engine problems. These can rank anywhere from something small like an intake gasket to head gasket to the big one, the cracked block. I doubt it is a cracked block, but blown gaskets are common if you have coolent in the oil.

If you find you have a leak replace the part. Don't patch it with leak stoppers. The leak stoppers are great for emergencies, but I would not trust them for long term results because of the other things they can plug.

Sorry for the long message, I have been through all this on a previous vehicles I have owned, and most of them on a GM vehicle.

 

[410Fortune]

4.0L water pumps dont have weep holes I dont believe.
The stock cap on my 93 OHV was 16 or 17#, it should say on it.
the BG coolant system stop leak only works when the stuff hits the air, they claim it does not effect internal blockages and that it is actually good for the cooling system seals, gaskets and hoses. I tend to believe in BG products quite a bit from my experience.

 

[MarksSC94]

Yeah, 7psi is a very low cap. You should be using a 14 - 17. Looking in your owners manual or call a dealer. They will tell you what size cap to put on it. 7psi will let out the a lot of coolent.

 

[410Fortune]

I have a 7psi cap on my V8 Bronco II right now the water temp sits at 210 with a 195 thermo. I do not lose coolant to the resevoir more then normal.
If I was having overheating problems then I suspect I would, but putting a 14 or 17 pound cap on it would not solve my overheating issue.

 

[MarksSC94]

The problem with all the liquids is they expand some when they are heated. If you have a 7lb cap on the radiator and you aren't loosing coolent that is cool. The coolent probably isn't creating enough pressure or getting the coolent up to the cap to boil over in the res. If you aren't getting the pressure that that is great. I can only go on experience from previous problems I have had with cars. The only heating problem that I had with this one, my limited ex, was that it wouldn't heat up to temp. A change of t-stat fixed that. now it sits rock solid, but I can't tell you the temp because the guage only has CNH and now it sit right in the middle of N so that isn't bad.

 

[410Fortune]

no that isnt bad, its likely 210-215 degrees thats what the stock cooling system on these trucks runs at when working properly, no matter which engine.

 

[MarksSC94]

I checked mine and I found the weep hole. It is on the passenger side behind the pully. It is actually pretty hard to see and you can't see into it with out a mirror. I took a good though and saw that my pump is covered with oil. I may have a leaky timing cover or intake gasket. Now you see what you did, I had to look and find more problems that I have to fix.... hahaha...oh well, the wife will be made at me because I am sure I can wrangle a new tool out of having to fix it...

 

[ma96782]

Don't want to start a p!$$ing contest.

Figure this question of the radiator cap pressure, could be like the age old question, "What temp, thermostat is BEST to put in my vehicle?"

http://www.are.com.au/techtalk/coolants.htm

Note that the pressurized cap, raises the boiling point of the anti-freeze........of course you already knew that. Me, I'd stick with the factory spec radiator cap..........and fix what is wrong w/ the cooling system.

Aloha, Mark

 

[410Fortune]

I would too except my custom aluminum radiator cost $500+ and its fubared (internal weld failed = leak) for now th e7# cap and the BG is getting me by.....
Otherwise I would run the OEM pressure cap and do like you said, make sure the system is up to par.
I was suggesting a band aid really, not a permanent fix.

sometimes in these threads it may seem like a pissing contest or whatever, but I like to think of it as brainstorming really, text only is hard to interprit

 

[ma96782]

I like that..........BRAINSTORMIN'

Aloha, Mark

 

[StillKicken]

Mark...If your like me you love to work on your truck. One VERY important thing my dad taught me growing up when I helped him work on his cars...you ALWAYS buy a new tool when you do work to your vehicle!!!

 

[ma96782]

......you ALWAYS buy a new tool when you do work to your vehicle!!!

That one has me smilin' ear to ear.

Aloha, Mark

 

[Maniak]

Just to throw a monkey wrench in the the cap pressure debate..

Our Neon and Explorer would always bubble after it was parked on very hot days (105-110f).

I raised the cap pressure from 13psi to 16psi and now the boiling has gone away.. The only thing I can figure is that the heat soak was bringing up the pressure, high enough to force the fluid into the resevior. The resevior on the neon was cracked (and very hard to get to) so I went with the 16psi as a tempory fix. Since I had no problems with it, and Stant even says most systems can handle up to 19psi w/out a problem I went with the 16 on the explorer. That was over 100k miles ago..

~Mark