1994 302 running cold

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DonLawson84

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The last couple months my 94 bronco has been running below normal operating temp (usually in the center gap before the N in normal) and taking a while to get there.

Thermostat was less than a year old, I replaced it any way. Old stat looked fine, installed new and still running cool. It is installed the correct direction and seated properly.

The thermostat used to open around the M and run temp down to about N.

Either I'm crazy or there is another passage to circulate the coolant

 

Rons beast

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Hey Don,

You may be witnessing aging of the gauge and sending unit. There is no reasonable reason why your engine will run cooler if all the other circumstances are the same.

Have you cleaned the engine bay and rad?

Are the fan and shroud the same?

is the ambient temperature cooler that normal?

have you changed exhaust?

If the answer to all those are no, then its most likely the result of 25 year old components getting "tired"

You can always get a temp reading with an infrared temp gun. (they are pretty cheep now)  and be happy it isn't running too hot.

The gauge is not built to be accurate but rather an indicator of a range of acceptable temps.

Good Luck 

 

Seabronc

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Where do you live?  It is normal for the coolant temperature to run lower in the winter.Where you see the gauge leveling out is not the point at which the tstat opens. The point at which it levels out is above the opening temp of the tstat. That temperature is controlled by the efficiency of your cooling system, mainly the radiator and air flow through the radiator.  If it was running hotter than normal I would be concerned.  If the heater wasn't working well I would be concerned about the circulation of water to the heater.

:)>-

 

miesk5

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Yo Don,

As Ron & Fred advised.

Following by Ford for a 96, but same for your 94:

Engine Does Not Reach Normal Operating Temperature @ http://www.diesel-dave.com/vehic/manual/stj/stj33013.htm#c

Damaged thermostat.

Cooling fan.

GO to Pinpoint Test C.

CHECK FOR FROZEN FAN CLUTCH

Perform fan clutch test as outlined in Component Tests.

Did fan clutch pass test?

Yes GO to C2.

No REPLACE fan clutch. REFER to Cooling Fan Blade and Fan Clutch in the Removal and Installation portion of this section. miesk5 note, this requires a specific type of Strobe Light & Tachometer. Our local radiator repair shop does this test. See test @ http://www.diesel-dave.com/vehic/manual/stj/stj33014.htm#fccmp330

C2 CHECK THERMOSTAT OPERATION

Remove water thermostat and check opening temperature as outlined in this section.

Does water thermostat begin to open and become fully open at temperatures in the specifications at the end of this section?

Yes REINSTALL water thermostat and CHECK temperature gauge operation as outlined in Section 13-01. @ http://www.diesel-dave.com/vehic/manual/stj/stjd1018.htm#extract_1379 miesk5 note, requires 74 ohm & 7.9 ohm resistor.

No REPLACE thermostat.

A simpler test is to; "...Pull the R/Wh wire straight off the sender & ground it to the block, intake, or head. Then turn the key to RUN. If the needle pegs, replace the sender. If not, diagnose the circuit. Also, read this caption: TSB 95-13-02 Erratic Temperature Sender - Factory temperature senders with a date code before 2774 are known to be defective. The code is stamped into the side of the hex. The format is the Julian date + the last digit of the year, so that's the 277th day of 1994. So 0085 is good; 1934 is bad; 3034 is good; 2765 is good; 3582 is bad. The sender should test at 74 Ohms cold; 9.7 Ohms hot. If you're having trouble with your temp gauge, try to read the date off the sender before any other diagnosis. A new sender from NAPA is under $10..." by Stephen miesk5 note, price ismost likely higher now.

Sender Location Diagram by Gacknar (The Mall-Crawler, Jeremy, "Big grey megga beast") @

http://web.archive.org/web/20130522155833/http://www.supermotors.net/getfile/265237/original/GT-40%20lower%20intake.JPG

Sender Installation Location pic in a 93

Source: by spivster (Joe S) @ http://www.supermotors.net/registry/6944/23369

 
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DonLawson84

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There is nothing that was done that would have started the change. Just started noticing it out of nowhere.

Ambient temperature plays almost no role in where the gauge will rise to.

After reading your replys and running possible causes, I am thinking you are right with the sending unit or gauge issue.

Thank you, I will use your troubleshooting guide to try and figure it out, hopefully sometime soon

 

Seabronc

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There is nothing that was done that would have started the change. Just started noticing it out of nowhere.

Ambient temperature plays almost no role in where the gauge will rise to.

After reading your replys and running possible causes, I am thinking you are right with the sending unit or gauge issue.

Thank you, I will use your troubleshooting guide to try and figure it out, hopefully sometime soon
Ambient temperature defiantly has an effect on it.  That is why in some cases the airflow through the radiator has to be restricted.  Mine always run cooler in the Winter than in the Warmer months.

Sure it could be some other problem, but you will have to figure that out.  If you are not having cab heating problems, I wouldn't worry about it.

:)>-

 
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DonLawson84

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Last night I did not have time to trouble shoot and poke around. But I did open the hood, pull the connector from the temp sending unit then reconnect it and this morning the gauge is reading more accurate temperature (was on the N my entire commute)

I found rockauto has the connector with pigtails, I am going to order that and sending unit. Thank you for your help

 

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