I know a gun board is probably the wrong place to ask but....

My 89 Ford Bronco 5.8 is running on the cold side. Temp gauge goes up to the lowest portion of the guage and stays there, no matter what. Only during the hottest days of summer (110) go up to the normal range. I replaced the thermostat with no improvement. While doing so, I noticed the water pump had an outlet routed back into the pump, maybe allowing water to bypass the thermostat????? Would this cause it to run terminally cold? Ive had the truck for a year and dont know if someone jerry rigged the coolant routes. Anyone have any ideas?

I think that the outlet routed back to the water pump was done to bypass the heater core, more than likely due to a leak.

Try replacing the sending unit. Dunno 'bout that hose routed back into the H2O pump though, how big is it? Can you post a pic? Did it used to run hotter? Maybee that'd just the way it is?

Heater works fine.

Hose is about 3/4 in hose, similar caliber to that of heater hose. No pics to post, going for gold plan.

Better too cold than to hot.
The loop is likly as ARkie said, leaky heater core.
If that truck came with a 'Tow Package' this could be normal.
(put 1000lb in the back for a while and see if it runs warmer. [}:)])

SSD

Check here:
[url]http://www.ford-trucks.com[/url]

If your heater works, you should have 2 3/4" hoses going to the firewall, one send and one return from the heater core.  There should be some type of valve in one of the lines to shut down water flow to the heater core when the heater is not on. (I'm more familiar with chevys than fords)  if there is not a valve, water will run thru the heater core all the time and work as a secondary radiator.  On a chevy, the valve looks like a disk about 1 1/2" to 2" in diameter with a small vacuum hose going to it.  When your climate control is set to heat, vacuum is applied to the valve to open it, no vacuum it is closed.

HOLD EVERYTHING.  You said you have heat?  Good heat?  The kind that could defrost a windshield?  Can you lay your hand on the top of the motor after driving a few miles (either the plenum or the vavle covers)?

Do not rule out a faulty temperature sending unit.  This can be checked by jumping it with the key in the "ON" position.  If you still get nothing on the guage it could be the gauge.  

How many ports are on the water pump not including the two integral ports that mate against the block?

An interesting note is that a buddy of mine has a '97 Ford F350 Powerstroke Wrecker and the Temp gauge never even gets to the "N" portion of the guage's range where the word "NORMAL" appears.  Now that I think of it, I have never seen a Ford with a temp needle that cycles past the "O" in "NORMAL", except when over heating.

If I confused you, here is a concrete way to see if your motor is reaching operating temp.  With the motor COLD, remove the radiator cap.  Start the engine and let it run for about 20 minutes.  (YOU WILL LOSE SOME COOLANT)  After about 20 minutes, put a thermomitor needle in the coolant through the open radiator neck.  If the temp is well under 180 degress, you have issues...you probably have to address the bypass on the water pump.  

My feeling however, is that if you have good heat from the heater core, your motor is reaching operating temp, and the problem is with the temp sending unit, the temp guage, or the wiring between the two.

I'm pretty sure I can solve this mess for you.  If you have any questions on this post, feel free to email me at [email protected], as I may not be able to find this thread at a later date.

Edited to mention, I have no idea what the bypass hose on your water pump is going from or going to.  A picture would help.  The pump may fit your block, but is the wrong application for you vehicle, which would explain extra/unecessary outlets/inlets.

Not bad info for free...

I used to have some fords around that year. The short hose on the water pump is to bypass the thermostat - ran from the pump to just above the thermostat on mine. A couple of my rigs always seemed to run cold so I used to use an old trick of my dad's - put a piece of cardboard in front of the heater in the winter. Had ~ 1 1/2" or 2" holes about every 8-10" apart in the cardboard. That helped it warm up quicker in the winter.

Now, that being said, follow the other advice and check out the sending unit. That is probably where the discrepancy lies if you are getting good heat from the core.

NMSight

Actually, this being winter and all, it sounds like it is working just fine.

We do "the cardboard trick" up here when it gets really cold.

110 degree normal temp for a hot area in the summer is actually running pretty cool!

Now if there IS something wrong, [red]replace the thermostat[/red] with a QUALITY part...195 degree model. Chances are, that will give you more heat. Anything else is gauge or sending-unit related.

If you got good heat, I would definately have to agree with sending unit /wire/ gauge  A temp sending unit should be relitively cheap and easy to replace.

OK, what you need to do is get that thing up to about 70mph and then violently turn the wheel causing the vehicle to go into a roll.  Then sue Ford for 300 million dollars.  Buy a new truck. [:D]  Worked for one person so far.

BTW, soundsd like a bad sending unit/guage.  Don't worry about it.