I have a 1999 F-150 w/ the 4.6L Engine. From what I have gathered I have the "Romeo" engine (VIN designation "W") installed in the truck. I have only had the truck for 4 days now and I was noticing two things -

1. A few seconds after starting the engine, there is a series of about 4 or 5 chimes repeated 4 times. I have been able to determine that either the "Service Engine Soon" light is burned out or broken.

2. The engine coolant temperature gauge on the instrument cluster always reads halfway between Hot and Cold. From the moment the key is turned (even if you don't start the engine) until it is turned off the gauge always reads the same. I assumed it to be a faulty coolant temperature sending unit, so I purchased one from the dealership (~ $11.00). When I went to replace the sending unit - I could not find the one on the engine. The Haynes manual says it is supposed to be on the "left front of the intake manifold", but there is nothing there but a metal plug. I can't even find the wires that connect to the sending unit. Is it possible that the sending unit is under/behind the alternator? I ask because I noticed two sets of wires going to something under there that I cannot see without removing the alternator.

I apologize for the long post, but if anyone could help me out, I would greatly appreciate it.

Thanks,
-J.T.

P.S. - I was able to connect a scanner to the truck to check for any codes and the only one I found was P1401 (DPFE Circuit High), so I have already replaced the DPFE sensor.

 

Welcome.

The gauges on these trucks are mostly fake. They are connected to the idiot lights.

Are you sure you are looking at the correct gauge? The temp gauge is real however it is highly dampened so it doesn't move erradically. But it will move up slowly as the engine heats up. The Alt and Oil gauges will move right to the middle even with the engine off.

To test your check engine light just turn the key to just before start and all the lights will light up and stay lit until you start the engine. This is the test outlined in the owners manual. There should be two check engine lights, one red and one yellow.

Follow your uper radiator hose towards the engine, where it connects you should find the temp gauge sending unit as well as the temp sending unit for the PCM.

 

hcmq,

I was checking to make sure that all the idiot lights were working when I realized that the "Check Engine Soon" light was not coming on when I turned the key to the "on" position without starting the car. It took me a while to find where in the instrument cluster it was supposed to be, but I verified several times that it would not come on. My next step here is to remove the instrument cluster and replace the bulb in that position.

The coolant temperature gauge immediately goes to the midway point even when the engine is completely cold. It does not gradually move from cold to normal as the engine warms up. I have used a friends scanner to confirm this because we watched the coolant temperature go from 70 degrees to 180+ degrees on the scanner while the gauge reported the same position the entire time.

Following the upper radiator hose to the engine leads me to the thermostat. It is located to the right (looking at the engine from the front of the truck) of the alternator. The only wires I found in that immediate area where for the front spark plug and the front injector. There are two other sets of wires running past the thermostat housing and under the alternator - could that be where the sending unit is located?

Thanks,
-J.T.

P.S. - I don't have an owner's manual for the truck yet, but I have ordered one from Helm along with the shop manuals.

 

On my wifes '96 Cougar...with a 4.6, I'm told there are three temp sensors;
1 for the gauge,
1 for the fan, and
1 for the brain box.

I can see two of them easily...
1 is on the passenger's side of the engine, on top of the front water passage of the intake manifold, and
1 is next to the thermostat, on the engine side, again on top.

I was told that the third one is either on the radiator somewhere, or on a cylinder head.

A mechanic said that they each have a different color plastic connector, and either two or three wires.

Which is which? Got me!
Hope this helps.

MR

 

Sorry...Double post for some reason.

 

Welcome to F150 Online.

My truck's gauges behave differently than those in HCMQ's truck.

If I turn the key on, without starting my truck, the fuel and battery gauges are the only ones that move.

Once I start the truck, the oil pressure gauge moves up immediately, and as the truck warms up the temperature gauge moves up as well.

I would suspect that there are three possible problems with your truck: Either the gauge itself is malfunctioning, the temperature sending unit is bad, or the wiring to the sending unit has a ground on it.

According to my Haynes manual, the sending unit for the gauge is at the left front of the intake manifold, screwed straight down from the top.

Good luck and keep us posted.

 

B-Man,

My gauges (fuel and battery) function that same as yours if I only move the key to the "on" position. However, my water temperature gauge goes to the midway position at the same time.


My oil pressure gauge functions normally when the truck is turned on.

I have double and triple checked my Haynes manual as well and still have not been able to successfully locate the coolant temperature sending unit. All I have found so far is that there are two holes in the intake manifold to the left of the alternator (passenger side), both holes are capped off. To the right of the alternator (driver's side) all I can find is the thermostat housing and the main coolant hose from the radiator to the engine.

I am totally at a loss at this point...

 

The chimesyou are hearing might be the SRS Supplemental Restraint System or air bags trying to tell you that it has a problem but the light is not working. Have a mechanic with a proper scan tool check it out. While he is at it he can command the the HEC to show various temps to test the Instrument cluster. BTW I believe the 99 + trucks use the Cylinder Head Temp to control the guage. It is screwed into the Cylinder Head behind the Alternator on the Driver side head.

Regards

Jean Marc Chartier

 

JMC,

Thanks - you have been the first one to respond about the chiming. I'll take your advice and have it checked.

I was beginning to suspect that the sending unit was under/behind the alternator, but I did not want to remove everything just to find out I was wrong.

Thanks again for you help.
-J.T.

 

Well I got the alternator out of the way and went to change the sending unit this evening only to find out that the connector and the part that I received from the dealership do not match. It is too late to call the parts department and have them double check the part, so it will have to wait until tomorrow.

Just as a sanity check, can anyone who has a 99 F-150 with the 4.6L V8, check to see if they have anything mounted on the passenger side of the intake manifold (directly on the top front portion left of the alternator). If you have two bolts/caps there (possibly with dark red thread sealer around the threads going into the manifold), please let me know one way or the other.

Thanks,
-J.T.