Go Back   F150online Forums > Powertrain & Mechanical > V8 Engines
Sign in using an external account
Register Forgot Password?
Register Photos Vin Decoder FAQ Members Search Today's Posts Mark Forums Read Vendor DirectoryGarage

Welcome to F150Online Forums!
Welcome to F150Online.com.

You are currently viewing our forums as a guest, which gives you limited access to view most discussions and access our other features. By joining our community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join the F150Online Forums community today!





Reply
 
 
 
 
Thread Tools Search this Thread Display Modes
  #1  
Old 06-28-2006, 08:58 AM
Member
Garage is empty, add now
 
Join Date: Jul 2005
Location: Richmond, Virginia
Vehicle: 1994 Ford F150
Posts: 31
1994 F150 4.9L 300 Temperature Gauge

I've had my '94 since it was new and put over 140,000 miles on it (5 speed manual transmission (M5OD)). For the first ten years or so the temp. gauge always stayed between 5 - 10% of the "NORMAL" range - actually below the N in NORMAL. The ambient temperature never mattered and the A/C on or off seemed to have no effect. During the past two years, or so, the gauge has crept up and now usually the needle sits over the O or R - about 40% of the range.

Over the years I have replaced the radiator (due to a leak at the aluminum/plastic interface), upper and lower rad. hoses (as a precaution, not a failure), coolant (water) pump (due to a leak at the shaft seal), thermostat (when the water pump was replaced - not due to a failure) and the drive (fan) belt (every 40k miles or so, never due to a failure). I've replaced the coolant six or seven times (approx. every two years) with 50/50 to 60/40 Prestone and distilled water but I've never used any of those "flush" products. It always comes out looking just like it went in - clean and translucent green. When I replaced the water pump I could see into the engine to the first cyclinder (I could put my fist in there) and the cast iron looked brand new - no scale, corrosion, etc.

What are your thoughts on the temp. increase? Real or instrument error? If corrosion on an electrical connection increases resistance in the circuit would that give a higher or lower reading. If real, what should I check or replace.

Great forum. Any thoughts appreciated.

Last edited by mradclif; 06-28-2006 at 09:00 AM.
Reply With Quote
  #2  
Old 06-28-2006, 11:04 AM
Senior Member
Garage is empty, add now
 
Join Date: May 2006
Location: British Columbia
Vehicle: 1992 Ford F-150
Posts: 268
Are you still using the same type of fuel? If you were running a different octane, that might make the truck run hotter (not sure which direction that'd work in) - are you using hotter plugs maybe?

Your temps are still well within range though, I have an older 92 I bought cheap and so am working my way through its issues and it has gone over halfway at times uphill on a hot day with the ac running - I'm going to switch over to an electric fan for better mileage/power etc...

As an engine wears, it may run differently, but personally I like your theory of the gauge or the sender unit altering with age, I'm not sure how sender units work, but as you observed, corrosion, age etc can result in increased resistance which might account for it.

You didn't mention the health of your heater core but everything sounds good, I suppose you could try a full-on flush and see what that does. personally I'd try to read the temps with a high accuracy thermometer and compare it with what's accepted as factory standard temp (anyone?) and continue to keep an eye on it...being as vigilant as you are, you're bound to catch any issues early.
Reply With Quote
  #3  
Old 06-28-2006, 01:19 PM
Senior Member
Garage is empty, add now
 
Join Date: Dec 2004
Location: Dover AFB DE / Harrisburg PA
Vehicle: 11 FULLsize ole' Ford rigs
Posts: 4,927
Send a message via AIM to adrianspeeder Send a message via MSN to adrianspeeder Send a message via Yahoo to adrianspeeder
Trouble is the gauge is nothing more than an idiot light with a needle. Heck even the oil pressure gauge is designed not to move. Add an actual water temp gauge if your wondering about it.

Adrianspeeder
__________________
Reply With Quote
  #4  
Old 06-28-2006, 05:31 PM
Senior Member
2010 Ford F-150
 
Join Date: Jul 2005
Vehicle: 2010 Ford F150
Posts: 183
Try replacing the sending unit.
Reply With Quote
  #5  
Old 07-01-2006, 02:39 AM
Senior Member
Garage is empty, add now
 
Join Date: Sep 1999
Location: Ventura, California
Vehicle: 1995 Ford F150
Posts: 3,083
Quote:
Originally Posted by adrianspeeder
Trouble is the gauge is nothing more than an idiot light with a needle. Heck even the oil pressure gauge is designed not to move. Add an actual water temp gauge if your wondering about it.

Adrianspeeder

Are you sure about that? The '92-up trucks I've seen had functioning water temp gauges. I know my '95 does.



Quote:
Originally Posted by mradclif
I've replaced the coolant six or seven times (approx. every two years) with 50/50 to 60/40 Prestone and distilled water but I've never used any of those "flush" products.
Coolant actually retains more heat than water does. Running a 60/40 mix might have something to do with it. Regardless, the only way to know for sure is to verify the actual temps, either with an infrared temp gun or an aftermarket gauge.
__________________
Webmaster:
Rice Haters Club

My F-150 Gallery



'95 Eddie Bauer F-150 SC SB / 4.9L / 5spd / 3.55 LS / K&N FIPK w/ Ram Air / JET / Crane / Taylor / Comp Cams / Edelbrock RPM / Hurst / Add-A-Leaf / Bilstein / Bridgestone Dueler A/T Revo 31x10.5R15's / Auto Meter Sport Comp Vac, Volt, Water, Oil & Fuel PSI / K.C. / Optima Yellow / Alpine / Apple / Toshiba / Boston Acoustics / Polk / Bazooka / And more...
Reply With Quote
  #6  
Old 07-01-2006, 03:06 AM
Senior Member
Garage is empty, add now
 
Join Date: May 2006
Location: British Columbia
Vehicle: 1992 Ford F-150
Posts: 268
My Ford Telstar factory manual had a procedure for verifying the performance of the gauge, basically, a resistance substitution wheel so you could vary the current input and see how it deflected the needle.

My temp gauge always stuck to the same spot regardless, it would shift slightly if I turned on the heater. I suspected the gauge wasn't working properly and tested it, and it passed. Then some time later, my thermostat jammed shut, and suddenly the temp gauge shot up impressively.

Ok, it's a bit more than an idiot light, but it seems far from accurate. Are we surprised?
Reply With Quote
  #7  
Old 07-01-2006, 04:59 AM
Senior Member
Garage is empty, add now
 
Join Date: Sep 1999
Location: Ventura, California
Vehicle: 1995 Ford F150
Posts: 3,083
Quote:
Originally Posted by pjb999@yahoo.co
Ok, it's a bit more than an idiot light, but it seems far from accurate. Are we surprised?
True. That's why I don't rely on mine.

Click the image to open in full size.
__________________
Webmaster:
Rice Haters Club

My F-150 Gallery



'95 Eddie Bauer F-150 SC SB / 4.9L / 5spd / 3.55 LS / K&N FIPK w/ Ram Air / JET / Crane / Taylor / Comp Cams / Edelbrock RPM / Hurst / Add-A-Leaf / Bilstein / Bridgestone Dueler A/T Revo 31x10.5R15's / Auto Meter Sport Comp Vac, Volt, Water, Oil & Fuel PSI / K.C. / Optima Yellow / Alpine / Apple / Toshiba / Boston Acoustics / Polk / Bazooka / And more...
Reply With Quote
  #8  
Old 07-06-2006, 07:49 PM
Junior Member
Garage is empty, add now
 
Join Date: Jul 2006
Location: NJ
Vehicle: 2002 Ford F150
Posts: 3
I had a 92 4.9L and had the same problem. Turned out to be the sending unit. I replaced it and temp gauge started reading correctly again.
Reply With Quote
  #9  
Old 07-07-2006, 03:02 AM
Senior Member
Garage is empty, add now
 
Join Date: May 2006
Location: British Columbia
Vehicle: 1992 Ford F-150
Posts: 268
A good point - a temp gauge is only going to be as accurate as the sending unit.
Reply With Quote
Old 07-07-2006, 03:02 AM


 
 
 
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


All times are GMT -4. The time now is 05:47 AM.


 
This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford is a registered trademark of the Ford Motor Company
Contact Us Advertising Privacy Statement Terms of Service Jobs Forum Text Archives
Emails & Contact Details