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1992 Ford Bronco Thermostat and heat

Tiny
BRONCOLOVER
  • MEMBER
  • 1992 FORD BRONCO
  • V8
  • 4WD
  • AUTOMATIC
  • 217,100 MILES
What are the commom sypmtoms of a thermostat going bad? Also, my heater, on high never gets really warm, just lukewarm. I can leave my truck running for fifteen to twenty minutes and all but the upper radiator hose which stays cold and the outside heater core hose that only gets slightly warm to the touch and inside is maybe 65 degrees.

I live in wyoming and it's only getting colder here,
-30F wind chill last night and my truck doesn't have a garage to live in. I have a block heater but it's just gone out.

I've noticed coolant leaking out the thermostat housing and I'm wondering if that's because it's stuck. Not to mention coolant is coming out of the bottom of the water pump that I just replaced a few months ago.

Any help is appreciated. Thanks.

Also it's the 351 windsor if that makes any difference.
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Wednesday, January 23rd, 2008 AT 10:56 AM

17 Replies

Tiny
RASMATAZ
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Replace the thermostat now and for the leak at the water pumper if its coming from the mounting flange tighten it -if its at the weep hole-replace the water pump.
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Wednesday, January 23rd, 2008 AT 4:44 PM
Tiny
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Ok I will do that, also, my heater problem also includes a fan that hardly puts out. Like on low you can't hardly feel it and when it's on high it blows what you'd normally feel on low. Could this be a motor going out or what do you think?
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Thursday, January 24th, 2008 AT 7:58 AM
Tiny
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. Like on low you can't hardly feel it and when it's on high it blows what you'd normally feel on low. Could this be a motor going out or what do you think?

Try direct power to the blower motor if it blows higher, replace the blower resistor
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Thursday, January 24th, 2008 AT 12:43 PM
Tiny
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Ok, haven't had the chance to do the blower motor yet, gotta find it in my manual and engine, bear with me here.

As far as the thermostat, I got it replaced, put a new gasket and everything on it, but now my temp gauge goes from the N in normal to the R every time I push on the gas, and the check engine light comes on. Can you tell me where the connector is for the scanner? The autozone said they can only do 94's and later I think, and I want the excuse for my wife to let me just buy a scanner for it.

Thanks for your help.
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Friday, January 25th, 2008 AT 4:55 PM
Tiny
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Its under the dash see picture below


https://www.2carpros.com/forum/automotive_pictures/12900_IMG_0042_2.jpg

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Friday, January 25th, 2008 AT 8:07 PM
Tiny
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Don't mean to correct you but the connection for the diagnostic is on the drivers side fender towards the windshield.

Anyways, got the codes pulled and it gave me a 634 "MLP sensor voltage out of self-test range A/C on"?

And "173 HEGO Shows system always rich"

Is this part of the temperature issue or what do you think?
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Saturday, January 26th, 2008 AT 4:38 PM
Tiny
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I stand corrected-I gave you that bcuz yours was lil bit confusing-the best thing I could do is wait for you. Some of them are under the hood.

Enufff said- P0173 relates to an oxygen at Bank 2-sensor might not be switching get the fuel trimmings read out.

Also might want to check the engine coolant temperature sensor-this two are partners in crime on adjusting fuel demands.
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Saturday, January 26th, 2008 AT 6:32 PM
Tiny
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It's all good. Anyways back to the problem, I crawled under the truck to find my O2 sensor, assuming this is what you were referring to, and come to find out, when I had my exhaust done, headers, and full magnaflow 2.5" exhaust there is a connector on the bottom of the motor but no O2 in the exhaust. Could this be causing the error code?

If so, why would it be showing up now and not back when I got the work done? I figured it would be a bad temp sensor since it didn't start till after I replaced the thermostat so I was planning on replacing it anyways.
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Saturday, January 26th, 2008 AT 11:00 PM
Tiny
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Ok, I'm back. I just got done replacing the temp sensor, the one beside the a/c compressor on the intake manifold and no change. It still heats up when I rev the engine and falls. Though I have one question, is the coolant system supposed to build pressure? I only ask this because now my engine compartment is slightly cleaner with a greenish tint and so am I. Thank god it wasn't hot. :)

As far as the blower motor, I put direct power to it and there was no change, it came out like it was on high on all levels but I know that's cause it's full power and no relay. But it came out the same like before. Hope this helps.

Oh and the codes, do you have any idea what the 634 is for? I have no idea what the MLP is and I haven't used my a/c since July.
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Sunday, January 27th, 2008 AT 3:19 PM
Tiny
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From: broncolover
To: rasmataz
Posted: Sat Feb 02, 2008 1:24 am

Subject: Question for ya

Sorry to bother you, but I was just wondering if you would know or have anything that could show me the wiring for an o2 sensor for my bronco? I need to repair the harness and there's two white wires a black, and a grey wire and I don't know which white goes to the other. Thank you.

Been trying to verify your heated exhaust oxygen sensor and I'm coming up with different color wires-see below


https://www.2carpros.com/forum/automotive_pictures/12900_HEGO_1.jpg


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Saturday, February 2nd, 2008 AT 1:43 AM
Tiny
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Ya I went to check that out too, but it shows the other color wires which I'm gonna assume are the stock colors. This is a Bosch o2 sensor and it's black grey and white. The only thing I'm really concerned about is I've researched it as much as I can and I've found out that the white wires are for the heating element in the sensor and they're 12V, but it doesn't say anywhere which is positive and which is negative. I just don't want to mess anything up. Donation coming soon, I just need to wait for my paycheck. Thank you for your help.
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Saturday, February 2nd, 2008 AT 4:26 AM
Tiny
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See below how Heated Exhaust Oxygen Sensor is wired in -


https://www.2carpros.com/forum/automotive_pictures/12900_ox_1.jpg

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Saturday, February 2nd, 2008 AT 1:41 PM
Tiny
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Ok, I know you're only trying to help, and I'm sorry, but I have no idea what that is showing me. I see it says heated o2 sensor and ground symbols but that really doesn't show me which wires go where. I'm trying.
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Saturday, February 2nd, 2008 AT 4:33 PM
Tiny
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Hook the white wire that has power on the heater circuit the other wire should go back to the computer. Or trace the wires back to the computer and determine which is the ground between the two.
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Saturday, February 2nd, 2008 AT 8:55 PM
Tiny
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Pictures!


https://www.2carpros.com/forum/automotive_pictures/84549_1_1.jpg



That's the O2 sensor side. the grey and black wire have been taken care of, no problem there. Like I said it's the white ones that are giving me the problem.


https://www.2carpros.com/forum/automotive_pictures/84549_2_1.jpg



That's what I plug into the connector on the bottom of the engine. There are no markings of any kind on these two white wires, though they were connected to the ones on the O2 sensor, I cut them all because the solder I have is a butane torch that was melting the wires while I soldered the other and I was stupid enough not to mark them. I just need to know if it would matter if I hooked these to the ones coming out of the o2 sensor backwards or if I'm really lucky it would be like before I cut it and get it right. I just don't want to have wasted $50 to have to do this again.
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Saturday, February 2nd, 2008 AT 11:32 PM
Tiny
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Well after all this time and hassle I found it. Though it's not the exact same one for my truck, but it's the same design and the same simple answer.

* Since there is no polarity to the heaters, it is only important to match the color of the heater wires.

So I'll just finish wiring it and have it put in and hopefully that will solve the c.E.L. And the gas mileage. Thank you for your help I will be donating as soon as I get my paycheck. Thanks again!
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Saturday, February 2nd, 2008 AT 11:50 PM
Tiny
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That's why I gave you the diagram-the heater has a resistor so either way it would worked. I'm glad you sorted all out-Good Luck
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Sunday, February 3rd, 2008 AT 2:51 PM

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