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I need some serious guru assistance before I do something drastic.
I have a 93 F-250. 7.5L gas, manual trans
When I bought the truck it had been sitting for several years, but only had 130k, started right up and ran strong. I did typical tuneup stuff after I
bought it; plugs, wires, cap and rotor, filters and fluids and brake pads/shoes.
When the weather started to cool last winter I noticed the truck wasn’t getting up to operating temperature. Not typically an issue 460’s are known to have. I don’t know why I had the feeling, but my suspicion was confirmed when I pulled the thermostat housing off. The thermostat had been gutted. I’m guessing by the now-deceased son of the original owner. Original owner “never took anything off that damn truck”… The air pump had also been removed when I bought the truck. Beyond the missing air pump, a head unit, brake controller, alloy wheels and bilstein shocks the truck is entirely stock.
I went ahead and flushed the cooling system and put new coolant in with a 195 degree thermostat. The heat worked great and I thought things were good.
The first time I did the brakes I followed the advice most give. After taking the brake drums off I left one side intact to reference. Somebody before me had not taken that same advice and swapped the star screws from their correct orientation. That and deteriorating brake lines made my life interesting on several occasions with the brakes alternating between working great, not working at all and completely locking up. At this point I’ve replaced everything BUT the original hard lines and believe I am past my brake problems. I bought a gallon of brake fluid and once I had clear, fresh brake fluid at all the bleeders I just started over and kept going until the jug was empty.
I noticed that the temp gauge showed pretty high temps several of the times I found myself on the side of the road trying to get the brakes unlocked. That didn’t seem too out of place, seeing as trying to drive through locked-on brakes will obviously make the engine work harder.
However, now that the brakes are almost totally new and no longer giving me trouble, I still periodically watch the temp gauge climb very fast towards the high end of the scale. Turning the heat on, if it wasn’t already, appears to help… sometimes. Sometimes not. I know better than to let the needle hit the red, the gauge will climb fast towards it, and stop halfway between the “L” of normal and end of the normal scale.
As soon as the temp gauge levels out at its highest point it drops right back to the “O” in normal. This has happened driving at speed on the highway, as well as in stop and go traffic.
Now the idle is fluctuating along with the temp gauge. Idle goes up, temp gauge reading goes up, then they both come down. Annoying when it happens once in a while, but it’s getting far worse and more frequent.
Now to the strangest part of all. I did something incredibly stupid a few weeks ago… When the temp gauge started creeping up and the idle got higher, I pulled off the road, opened the hood, stuck my hand on a just hotter than warm radiator cap and said screw it. The only thing about this truck that seemed close to being too hot was the temperature gauge.
I turned the radiator cap, bare-handed, the first click and heard pressure release. Turning it the rest of the way and no geyser, no trip to the ER… just an engine as not hot as everything but the temp gauge indicated.
Maybe the sensor is going bad? After a bit of research I found out that for a few years Ford used two coolant temp sensors, one sends info to the gauge, the other to the ECU. My local NAPA had both in stock, so I figured why not, do both.
The problem is still happening.
To be honest, it’s getting worse. This condition is happening more frequently, the elevated idle is getting higher and the temp gauge is pushing closer and closer to the red.
Last week I made sure to have my laser thermometer with me, it’s gotten hot early this year and I really don’t want the truck ACTUALLY overheating. I trust my nose, but not completely. That’s why there’s a temp gauge, right?
Well, irrespective of what that gauge tells my eyes, the thermometer supports what my nose is telling me, the truck isn’t actually even hot. All my senses agree that the idle is more or less what the tach says though…
As much as I really hate just throwing parts at a problem, there are only so many things giving inputs to the injection system and sensors are cheap, whereas melted down engines and 10mpg (on their best day) engines that idle at 1500 rpm periodically are not. Not with $4/gallon gas.
So this weekend I decided to first, just clean the engine and compartment, as I would be replacing the IAC and TPS, in hopes they would help my problems. As of tonight every vacuum line is brand new as well. I also pulled out the intake air charge sensor it had a fair amount of oily crap built up and it, but my NAPA didn’t have that one in stock, so I just cleaned it up and stuck I back in.
And still, getting off at my exit to go home, the temp gauge is nearing the red and the idle is up. Then it goes down. New for today are the two no longer working in total harmony. I’ve seen the idle go up while the temp gauge needle stays at its happy place covering.
I guess I’m glad I didn’t make things worse today, but I would really like to fix this problem.
A few pictures:
As I parked
Idle is climbing
Temp gauge follows.
Pop the hood and have a look. It’s dark and the laser point of the thermometer didn’t show up as well as I had hoped:
188 degrees at the filler neck
187 degrees on the upper radiator hose
212 on the metal of the thermostat housing.
I can tell that the thermostat opens around “R” on the temp gauge, so I assume that’s 190-195 degrees or so. I imagine the end of the normal scale to be 230-235 degrees and the start of the red to be 240-250? Somewhere in there?
I’m not super worried that I’m actually overheating now, but I would like to have a temp gauge I can somewhat trust before summer rolls around.
The erratic and high idle is definitely something I want to not happen, especially as it isn’t just an idle issue. When this condition occurs at speed, while much less noticeable, it does affect the truck driving. On the interstate holding 70, it’s barely noticeable. In traffic it is much more noticeable. So far it hasn’t happened in crawling traffic during rush hour, but there’s a big difference between *ACTUALLY* idling along, just keeping the engine from stalling to trying the same when the engine is idling at 1500rpm.
Occasionally the check engine light will come on in tandem with the temp gauge creeping up. It seems the light coming on is more likely to happen when I’m driving at speed. I’ve been reading up on pulling codes from the EEC and plan to make that happen this week. I’m not sure what, if anything, I’ll learn from that as I’m not sure if any codes get stored unless the light stays on.
I really like the truck overall, good thing as there’s no way I’d be able to sell it with whatever is going on right now.
how is your alternator connections, grounds everywhere, and hows your belt tension/condition and tensioner behavior while running(plus you have a manually tensioned alt yes?)
I do not believe the alternator is manually tensioned. Too dark at the moment to check, but I will see.
None of any connectors I’ve pulled chasing this issue have shown anything concerning to me.
Voltmeter in the dash notwithstanding, my Fluke multimeter says the alternator might be a *little* hot I believe it was putting out almost 14.6 V.
As far as belt running, I neglected to add that new belts were part of my initial tuneup work. I didn’t replace either idler, as they both ran smooth.
All of the grounds are present, with nothing to indicate an issue there. I do like your line of questioning as I fully believe I have a “ghost in the machine” electrical problem.
Cautious optimism here, but I’m hoping it’ll be the forum for the win.
I got a chance to pop the hood on the truck earlier this evening and look closer at the grounds. I’m not sure where Ford originally ran the engine grounding strap. I’m certain it’s position on the firewall is correct, just as much as I’m certain it didn’t run to the air-pump mounting bracket atop. Yep… that’s where it was… under a just more than finger-tight bolt, on the painted bracket.
That bracket attaches to an exhaust stud and intake stud, both double-nutted. I loosened the second nut on the intake side and unfortunately found that the corresponding exhaust stud was broken. I’m guessing the PO’s son made an attempt to remove the bracket when he ditched the air pump and either broke said stud or started it down the road to breaking, in any case, THAT will remain a problem for future Jeremy. I wire-brushed the stud, put a dab of dielectric grease on the threads and used the nut to hold the engine ground down. Because the fender was replaced I figured there would be no harm in running another wire from that engine grounding spot on the firewall up the the ground by the battery on the passenger fender. Driving home afterwards things seemed much happier. Nice lopey idle, never higher than an indicated 1000 rpm. I took several opportunities to pull off and just sit with the engine idling twice on the drive and didn’t get any the the issues I’ve been seeing.
So… cautious optimism, as “I did it three times” seems to be my story where this truck is concerned thanks to the brakes. Hopefully this thread can end here.
