Fluctuating Water Temperature

[PHL Flash]

Does anyone have an idea for a fluctuating water temperature problem? The water temp gauge operates like a windshild wiper. I started a thread on this a few weeks ago, but I have tried a few new things since. And the problem remains.
System has been pressure tested, and no leaks detected. No sign of hydrocarbons in the coolant, and no indication of coolant in the exhaust. Thermostat has been replaced, as has the water pump, the temperature sending unit and the radiator. The heater core was replaced last February, and the radiator in April. None of these component changes made a difference. There is no appreciable coolant loss from the recovery tank, and no bubbles detected there.
My mechanic gave me a copt of TSB 95-18-5 titled 'Temperature Gauge Fluctuations and Inaccurate High Readings'. It said to change the gauge and sending unit. As the sending unit had been replaced with a Ford part, I went for the gauge. Ford wanted $175 for a gauge, a bit pricey. So I got an entire cluster from the junk yard and installed the gauge. The fluctuations continue, but the swing isn't as severe, going from below the 'N' up to the 'M'. Mechanic used a thermal sensor to identify the temperature swing as 180-220. The heat output fluctuates also, indicating the water temp change is accurate. I was going to bypass the heater, but I've got to wait till spring for that project.
Question is why does the temperature fluctuate? I am told it 'could' be the head gaskets, but I am hesitant to tear down the engine this time of year. If I knew for sure that is was the head gaskets, or the intake gasket, I would plan to change them in the spring. But engine has 145k on it, and it may be wise to rebuild or replace it, instead of just replacing the gaskets. Is there a definitive test, other than disappearing water or a massive leak, to point to the head gaskets? I have toyed with the idea of a replacement engine, rebuilt on the shop floor and just replaced on a weekend. But I would hate to go that route if there is another solution.
Thanks in advance and any help and expertise will be greatly appreciated.

 

[Eneurb]

I believe that TSB calls for a matched set of guage and sender. The wrecker cluster that you have purchased probably has the same part no. guage in it that you already had.

 

[PHL Flash]

Ah, right you are Eneurb. I didnt read it that close. It wants the 'kit' to replace both components. Interesting. However, this TSB concerns 'temperature indications'. I am quite certain the water temperature is really fluctuating, as indicated by both the heat output, and the mechanics thermal sensing. I am not at all convinced of it being only an indication problem, but I am at a loss. Aside from the obvious (thermostat opening) what would cause the temp to fluctuate so noticably? I will check check out the actual kit at the Ford dealer tomorrow, though I may be afraid to find out the cost. Thanks for the tip.

 

[Eneurb]

Look into an aftermarket temp. indication setup such as autometer. You could be having head or t-stat problems, and have nothing wrong with you gage.

 

[sabatosh]

Have you replaced the sensor yet? I'd say it's the sensor or a short/corrosion in the wiring to it. I wouldn't trust your mechanics any of them as far as I could throw them.

 

[PHL Flash]

I did replace the sensor, with a Ford part, but it made no difference. The water temp is really fluctuating as the thermostat opens and closes. I can feel the heat output (or lack thereof) with the changes. I personally dont believe it is an indication problem, but I just dont know enough about the internal workings and foibles of this engine. I do trust my mechanic as he is a good friend with many years of experience, though not all on Explorers. He really cant tell me what the problem is either. I thought someone with an Explorer may have had a similar experience. Thanks for the expertise and responses.

 

[jnealg]

this may sound stupid and I am no mechanic but I have a fairly analytical mind...

Could you have a bad new thermostat? It seems to me that it should be opening before 200 degrees so maybe it is sticking then "popping open". What happens when you boil it does it open at the right temps?
Next I'd look at flow, check for restrictions. I've heard bad radiator caps causing fluctuations.
I wouldnt run long this way but I'd pull the thermo to see if the temp still moves or remains steadily low like it should.

 

[PHL Flash]

jnealg -- I have put in three thermostats recently, one from AutoZone and the others from Ford. It makes no difference with this problem. When the indicator reaches about the 'L' on the gauge, the thermostat opens, and in three seconds, the indicator drops like a stone and points down below the 'N'. And the heat output disappears. Then, the thermostat closes, water gets warmer, heat returns and the cycle repeats itself. Usually, my eyes are glued to the gauge, ready to shut down, should that gauge continue to climb past the 'L', and not drop off. As for the cap, it was replaced last month, and made no difference. And, this problem, the temperature indicator swinging like a windshield wiper with water temp fluctuations, has been present for at least 3-4 YEARS in some form. It is only recently that the temp swings were getting more pronounced. The sweeps became very drastic and noticible. After my mechanic checked the system and found no apparent obvious problems or leaks, he suggested changing the water pump. It was the original, so I thought I'd give it a go. The problem persists, however, though not as drastic. The old water pump looked totally normal to my naked eye. I am perplexed, but am hesitant to tear down the motor unless I can nail down the cause. I cant afford the down time right now. Thanks for your observations. I really do appreciate it.

 

[gss]

How is your hoses? Is there any chance one is getting sucked flat and then opens back up at higher temp as the water builds up pressure?

 

[jim blair]

I have a friend who cured this same problem with a new radiator cap. aparently they do go bad even tho i have never had one go bad.

 

[sabatosh]

Well if you aren't losing any coolant, then the only problem you can possibly have is with circulation or air in the system. My sister was having temperature swings with her car overheating after some tune up maintenance. Apparently they had not tightened the cap good. It's possible that you have some sort of blockage in the engine something broken off in the water jacket that's making it difficult for the water to pressurize, then the pressure gets high and the pump reliefs and then the pressure drops it unclogs and the same cycle over and over.

It has to be something loose flying around in the water jacket of the engine that's obstructing coolant flow. That's the only thing that really makes sense to me at this point.

 

[agzaretzka]

I'm curious. Does the water temp stay consistent if you run without the thermostat?

 

[PHL Flash]

I did change the cap last month, with no noticable change. Symtoms remained. As for removing the thermostat, the weather has again turned cold in NJ, so that is a project that will have to wait a couple months. Someone suggested changing the clutch fan, that a sticking clutch fan could cause these symtoms. So I am thinking of changing that as it is the original. Thanks for all your ideas.

 

[Eneurb]

I'm curious. Does the water temp stay consistent if you run without the thermostat?

Be careful if you are going to run without a thermostat. Without the restriction in the system, coolant can flow to quickly to effectively transfer heat. IMHO.

 

[TN_Explorer]

Something to try

I have a coworker who recently had a very similar problem with a Probe. To cut to the punch line, the Haynes manual shows the toggle valve at the top, which he had been doing. This puts the bulb that controls the thermostat at the bottom. It turns out (in the Probe anyway) this puts the bulb close to the head and at the bottom of the flow. The result was a thermostat that stayed open most of the time, but that fluctuated wildly.

He cured the problem by turning the thermostat 45 degrees to move the bulb into the cooler water flow, and it stopped the fluctuating. Don't know if it will help, but as much as you've been through, it couldn't hurt to try it.

-- Good luck!

We all want to know what this finally turns out to be!

 

[vrytired]

Be careful if you are going to run without a thermostat. Without the restriction in the system, coolant can flow to quickly to effectively transfer heat. IMHO.

wtf??

i understand that its your opinion but thats just dumb

Q = M x C x Delta T


laws of thermodynamics say that faster flow = better cooling

 

[Eneurb]

Dumb is such a harsh word... heat up the burner on your stove... red hot... then quickly run your right hand over it... now take your left hand and place it on the burner and don't move it. Which hand is burnt more???

 

[sabatosh]

I'll vouch for that, the water moving at a higher current won't slowly cool off in the rad or pick up heat in the motor. It does sound like the thermostat isn't sitting right, that's similar to the water jacket ports being intermittently clogged with some debris. But I don't know physically the problem to look at possibilities to determine why it's behaving as such and is defective. But the irregular flow has to be caused by something clogged obviously in the only thing that could be since the heater core hoses and rad are new. The thermo or something in the water jacket...by some odd means...I don't know what could be in there.

 

[msmyth]

I'm having the same problem in my 92. Changed the engine a year ago, ever since the guage has been rising and falling. No change in heat output though. Everything's new. Radiator, t-stat, water pump, fan clutch. Not loosing any coolant. Everyone I talk to is totally at a loss. Somebody....help!

 

[rustbeltlife]

There can be a blown head gasket, and still have no coolant loss. We see this occasionally at our shop. Our best tool to detect this is our radiator pressure tester.