Cooling System Problem

[PHL Flash]

HELP! On my 93 Eddie Bauer, with 143k -- water temp guage fluctuates like a windshield wiper. First I replaced the thermostat, with a Ford part. No change. Then I replaced the sending unit. No change. Now I replaced the original water pump. No change.
I took it to my mechanic who thought it was an intake manifold leak and pressure tested the system, with no bleed down, indicating no leaks. Then he replaced the thermostat and the cap. He tested the water for exhaust gases, and found nothing. He tested the water temp, and saw that the temp varies between 180 and 230. He recommended changing the water pump, so I did. No change.
The temp guage goes up to the 'L' of Normal on the guage, the thermostat opens and the temp drops down to the 'N'. And the cycle continues on and on.
HELP! Anyone ever have a similar problemor any ideas? Thanks in advance.

 

[aldive]

You appear to have eliminated many causes of your problem, however, have you checked/replaced the actual gauge itself?

 

[PHL Flash]

I did not replace the actual guage. I thought about it, but my mechanic used a thermal tester, which showed the water temp to be fluctuating, as the gauge indicated. He found the water temp change from 180 - 230.

 

[marragtop]

Are you losing any fluid at all? Have you replace the radiator cap? Just a thought...

 

[PHL Flash]

My mechanic replaced the radiator cap when he was testing the system. There is no coolant on the floor, hence no obvious leaks. Not positive, but I dont recall adding any coolant to the recovery tank. Initially, the mechanic thought it was an exhaust leak through the head gasket, but it passes the pressure test. That may still be the culprit.
Side note: It has begun pinging crazy under loads. Its actually quite loud and embarassing, such that my daughter wont drive it any more. I had the carbon burned off the cylinders, but it didnt really silence the pinging. Related?

 

[MrShorty]

Dirty MAF and/or Loose lower intake bolts are also common causes of ping. Lower intake bolts can also allow coolant leaks.

A bad fan clutch could conceivably cause similar behavior. Take the fan clutch off, unhook the outer end of the spring and rotate 1/4 turn CCW, reinstall the fan clutch and test drive to see if the problem is resolved.

I've also seen this kind of behavior from a clogged heater core. If the cooling system hasn't been flushed recently, you might try this.

 

[PHL Flash]

The heater core was replaced last Feburarydue to a leak. Problem was noticable prior to the core being replaced, though not as severe as today. Clutch fan -- fan still spins. How can I tell if the clutch fan is not functioning? I believe the MAF was cleaned when they ran the carbon cleaning process. Again, however, it did not silence the ping.
Side note -- Intake manifold gasket was replaced about 4 years ago so it is not original.

 

[PHL Flash]

Over tha past few months there has been little noticable coolant loss. Perhaps about a quarter of the recovery tank. Havent really noticaed any at all.

 

[MrShorty]

"How can I tell if the clutch fan is not functioning?"

A bad fan clutch could conceivably cause similar behavior. Take the fan clutch off, unhook the outer end of the spring and rotate 1/4 turn CCW, reinstall the fan clutch and test drive to see if the problem is resolved."

If this resolves the problem, then the fan clutch is bad. If the problem remains, then something else is to blame.

And, if it's been 4 years since the intake manifold has been dealt with, I would tighten the bolts, if only as preventive maintenance.

 

[Ira]

This is my experience with my 91. A few years ago, I replaced my t-stat. Before doing this, my temp would be all the way down when cold (as it should be), but after it warmed up, it would read about center scale, and stay there without moving. After changing the t-stat, my temp would swing similar to yours, from about O to A. I figure this is normal, as you can actually see when the t-stat is opening and closing, and the steady reading was because the old one didn't function as it should.

A couple things to consider...first, your gauge could swing farther on colder days than on warmer days due to the colder coolant being released from the radiator and dropping temps faster than on warmer days. Secondly, don't make the mistake of changing t-stat to a hotter or colder degree rating than engine calls for. If you put a colder one in, the temp will never reach hot enough temps that it is designed to run at and computer will change mixture/timing to try to compensate.

As for your pinging, is it possible that you had been running premium or plus fuel and then you put regular or bad (lower octane) fuel in it? The computer will adjust to the fuel used, and if you suddenly go from running a full tank of premium to regular or bad gas, you could experience pinging until the computer "gets a grip" on what's going on and eventually compensates. You could try disconnecting your battery for about 15 minutes and then reconnecting and see if that helps.

Something else that can cause pinging is carbon buildup. You said your de-carbonized the cylinders, but are you sure it was effective? If you get a severe carbon buildup in a cylinder/cylinders, you can develop pinging because of the carbon increasing the compression ratio by displacing the available cylinder volume. I would pull the spark plugs 1 at a time and compare them to see if you see a cylinder with significantly more carbon on the plug.

 

[jwilbur1]

I vote for another heater core. I had overheating problems in my 85 Bronco and after changing everything else I bypassed the heater core, problem solved. So I cut out the heater core housing inside the engine compartment, pulled out the heater core, inserted new one and repaired the heater core housing with JB Weld, problem fixed!

Pinging could be from coolant being too hot...

 

[PHL Flash]

Thank you all for your suggestions. First, I have never run anything but regular gas. I did disconnect the battery to try to reset the computer, but no difference. I will attend to the fan next chance I get. As for the heater core, the problem was evident before I changed the heater core. In fact, the guage has acted like a wiper for about two years. It is only recently that the swings are becoming more drastic. That is what worries me. I am afraid that one time it will go up to the 'L' and not come back down. As for the intake bolts, that may be my next stop, or perhaps the head gaskets. Thanks again for all your suggestions. There was a similar thread a few months which I will reread, but I believe that ended in the head gaskets.

 

[Lt.Jim]

I have a 94XLT. My water pump recently went out and just prior to that my temp indicator was doing the "wiper blade dance" I replaced the water pump thermostat and top hose. I also replaced the belt tensioner. If the belt is not staying tight the water pump will not flow properly this could cause the fluctuation in the temp.

 

[X-1]

The 91-94 explorers came with a 9 bladed fan, Fords replacement is a 10 bladed, they know they needed more cooling, also check yours for cracks, I had to replace mine, looked like it was getting ready to come apart. Secondly, if you have not changed the fan clutch, for every year old they loose 100 rpm's, these 2 items here with a radiator fluish should put your temp gauge on the cool side.

 

[Josh]

This may be stupid, but did you make sure the t-stat was in the right way. I believe the there is a vent hole in the t-stat that has to be on top. Also, make sure that the system is free of air pockets. Another words you need to burp the system. After that I would look at the clutch fan. I had heating problems with mine during the summer. I replaced the clutch and problem solved. I don't remember if my temp was fluctuating though.

 

[JeffMohr]

After having the same problem for the last few months I found the new thermostat I put in was bad....(don't buy the cheap ones). When I replaced it the gauge now is steady.

 

[Lloyd10977]

This may be stupid, but did you make sure the t-stat was in the right way. I believe the there is a vent hole in the t-stat that has to be on top. Also, make sure that the system is free of air pockets.

Some of the aftermarket thermostats do not have a vent hole. You can resolve that by drilling a hole in the edge of the thermostat, about 1/16-3/32", and remount the t-stat with the hole at the top. This essentially will work to bleed the system as the engine runs and help to reduce the drastic swings in temperature somewhat.

 

[wally43]

HELP! On my 93 Eddie Bauer, with 143k -- water temp guage fluctuates like a windshield wiper. First I replaced the thermostat, with a Ford part. No change. Then I replaced the sending unit. No change. Now I replaced the original water pump. No change.
I took it to my mechanic who thought it was an intake manifold leak and pressure tested the system, with no bleed down, indicating no leaks. Then he replaced the thermostat and the cap. He tested the water for exhaust gases, and found nothing. He tested the water temp, and saw that the temp varies between 180 and 230. He recommended changing the water pump, so I did. No change.
The temp guage goes up to the 'L' of Normal on the guage, the thermostat opens and the temp drops down to the 'N'. And the cycle continues on and on.
HELP! Anyone ever have a similar problemor any ideas? Thanks in advance.

My wife Explorer is doing the same thing. After reading all the replies I thought of something, did anyone think of checking the lower radiator hose. It could be collaping under pressure. Her truck's temperature guage does not fluctuate at idle but does when driving on the open road. She is loosing coolant from the recovery tank. I have replaced the fan clutch, belt, and idler pulley. These were all bad. I later replaced the radiator cap. It still does it. There is no coolant in the oil and the exhaust looks normal with no coolant smell. This truck has 99k miles you can't find a drop of oil or coolant around the engine. This is a vehical that will still be in the family for a long time.

 

[marragtop]

I suggest replacing the thermostat. This is a normal maintenance repair. Another thing to check... with the engine cold, take off the radiator cap and start it up. Give it some RPMs, and if water surges out of the radiator, you may have a blown head gasket.

 

[racinjason68]

mine does the same not all the way to the L though, and it happened after replacing the stat... the cheaper stats dont have the vent hole... It does help as temps vary under pressure.. I had also replaced heater core and radiator... Also you had said that the floor wasn't wet so the heater core must be ok....
Well if you have replaced the heater core you would see the lower cover has a weep hole that leads to the outside of the firewall.... Hince core leaks no wet carpet...