Head gasket question/cooling problem
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Elder User
Joined: Feb 2003
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From: Winnipeg Canada
Head gasket question/cooling problem
I'm having a cooling problem, temp is always fluctuating. Headgasket isnt blown, no signs on the plugs, no smoke out the back, fluid isnt missing. Thermostat was changed twice, but the problem still persists. I was thinking that maybe the head gasket was done before I bought it (I'm going to phone the previous owner tomorrow, but I thought I'd ask my question anyways) Anyways my question is, could the head gasket(s) be on backwards or something? It was just a thought that came to mind because I've heard that on 302's that when they go on backwards everything lines up except for a couple water holes that are slightly off, so maybe that could be the case. Although if that could be the problem, it will still be a bill that I'm not looking forward to.
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Joined: Dec 2004
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From: Churchville MD Harford co
Who says the head gasket isnt blown?
small head gasket leaks wont cause smoke or water in the oil
it can leak just enough to air lock the thermostat and overheat
check your oil cap and pcv valve for white goo
does the heat stop working when the temp gauge is high?
small head gasket leaks wont cause smoke or water in the oil
it can leak just enough to air lock the thermostat and overheat
check your oil cap and pcv valve for white goo
does the heat stop working when the temp gauge is high?
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Elder User
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From: Winnipeg Canada
It doesnt overheat. Gets up to halfway on the gauge then once I start driving it will go back down to the line above Cold. Will continue to do that while driving. I said it's not blown just by people saying check this and that, and it's not it, so I'm sure its not blown. I also had a new cap on there, but it did the same thing. Heat is always steady once the truck has warmed up, even when the gauge moves. What is the white goo? I'll look tomorrow.
Check engine light is on and it was codes P0133 and P0153, slow circuit response for o2 sensors.
Check engine light is on and it was codes P0133 and P0153, slow circuit response for o2 sensors.
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From: South Texas
I had the same problem on my 91 4.0. Changed the thermostat several times, different manufacturers, temp ranges and no help.
Now you are going to think I am crazy by what I suggest, but hang on a minute. As previously stated, most likely cause is air in the system.
My problem was a stopped up heater core that would not let water bypass the thermostat. If yours has a heater control water valve, make sure it is bypassing the water when shut off, if not, check that sufficient water is actually flowing in the heater core. Easy check is to re-route the heater hoses temporarily to totally bypass the heater core and valve. If this stops, (or diminishes the fluctuations) then find out which one of the 2 is the real culprit.
Could save you from pulling the heads.
Codes you have COULD be indication of antifreeze damaging the O2 sensors or just plain old age, but I would not replace them until you rule out headgasket leak.
Dialtone
Now you are going to think I am crazy by what I suggest, but hang on a minute. As previously stated, most likely cause is air in the system.
My problem was a stopped up heater core that would not let water bypass the thermostat. If yours has a heater control water valve, make sure it is bypassing the water when shut off, if not, check that sufficient water is actually flowing in the heater core. Easy check is to re-route the heater hoses temporarily to totally bypass the heater core and valve. If this stops, (or diminishes the fluctuations) then find out which one of the 2 is the real culprit.
Could save you from pulling the heads.
Codes you have COULD be indication of antifreeze damaging the O2 sensors or just plain old age, but I would not replace them until you rule out headgasket leak.
Dialtone
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Elder User
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From: Winnipeg Canada
Dialtone, guess what I just did today, turned off the heat and guess what, temp fluctuations went away. What a coincidence that you would post this and I tried it out myself. So if its a plugged up heater core, can I just flush it out or is it time for a new one?
Elder User
Joined: Aug 2001
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From: South Texas
OK, now figure out if the water control valve (if present) is bypassing in the "off" position, or the heater core is (partially, or fully) stopped up in the 'on' position. I found that flushing was not effective due to the core design. Once it stops up, the only real fix is to replace it. My 91 was cheap and easy, but you never gave us your details so cannot help much more with a cost esitmate. By your codes, I suspect yours is 96 or newer year (OBD-II) codes. Check Autozone web site for core cost for your year.
Dialtone
Dialtone
Last edited by Dialtone; Jan 1, 2006 at 11:23 AM.
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From: Winnipeg Canada
So today I was tinkering around with the engine bay...saw something leaking coolant that probably shouldnt be. Also, is this that water control valve??? Everytime you move the actuator it squirts out coolant a little
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Joined: May 2002
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From: Phoenix
So it looks like a couple of things. A clogged heater core and now a leaky flow control valve. Likely that the clogged flow caused the leak. A couple new components and you should be good to go.
Without the cause/effect you identified by turning the heater on and off and also finding this coolant leak, if there were no other symptoms, I'd be inclined to believe the engine coolant temp sensor was bad. But know that you can control the temp fluctuation, you need to look more at the heating circuit.
Let us know the final results.
Without the cause/effect you identified by turning the heater on and off and also finding this coolant leak, if there were no other symptoms, I'd be inclined to believe the engine coolant temp sensor was bad. But know that you can control the temp fluctuation, you need to look more at the heating circuit.
Let us know the final results.
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From: Phoenix
How to change a heater core? Hope you like being inverted on your back under the dash. Get a decent repair manual and it should be fairly straight forward. Make sure you get all the clips off the heater core/AC condensor housing box or you might crack it.
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