Hello I'm going to apologize for this long post but I have to come here for your guy's help. I'm not a mechanic but I know quite a bit about the 5.8 Windsor from taking it apart so many times. I'm going to start this question all the way back from when I started this project with my truck so you guys have a better idea of where I'm at now. I have a 1995 F150 5.8 liter Windsor XLT. My truck was bogging and had no power under load I mean I could not make it up a hill so I went through the whole game of replacing everything under the sun until I finally read the codes with Subfords advise and sure enough I had to replace my fuel injectors. While replacing my fuel injectors, since I had to be upper manifold off, I cleaned and replaced all hoses vacuum hoses some sensors that were clearly not working anymore and painted and cleaned everything. I ran my vacuum hoses a bit differently this time around with advise from another ford website. I finally started my truck about a month after I started this project and everything worked fine. Actually the truck felt better than it has in over 10 years that I've owned it. I did replace the thermostat I replaced the temperature sensor the temperature sender I also replaced a few coolant hoses that seems weak. The lower hose that I replaced does have a spring in it. The crossover hose I made out of some extra hose that I had here in my shop but seemed to work just fine. The truck ran fine for about a week or so but the temp gauge did start to climb a bit. I can't put my finger on exactly when the situation started but all the sudden my temp gauge would go from 180 to 240 in the blink of an eye. I found that if I gun it a few times it will immediately drop back to normal and if I turn the truck off and back on the temp drops right back to 185. If I drive a little farther the same thing keeps happening over and over. You get the picture. Ive read many posts here and elsewhere and I've changed and checked almost everything. Last week I was convinced that this was a head gasket issue and was about to start pulling the heads off but now I'm starting to think maybe it's not. I flushed and back flush my cooling system several times and I've used everything from a 165 to a 205 thermostats. I'm not getting any codes for this. Also my truck idles perfectly. It does have a manifold leak but nothing too crazy. It also drives fine and hasn't gone into limp mode at all. Also, I did install an aftermarket temperature gauge because I wanted to see if this was an electrical issue and the temperature is going from 180 to 240 and straight back down again. After running the truck for a while I pop the hood and safely remove the cap from the radiator and the fluid is really not that hot, it's hot but definitely not boiling. I did burp the system about a hundred different ways but I'm not saying that I did it correctly any of the times, I do think the system is definitely burped though. Im not getting coolant in the oil and my overflow is good. It doesn't seem to be losing coolant either. I will not stop looking until I find an answer to this problem so if any of you have anything new or interesting to tell me or add or maybe has the same situation with their truck please, anything you have to say is good information to me. One more quick thing to add is that I did have to replace that metal crossover pipe that sits on top of the radiator shroud because it started to leak and I replace that with a hose of the same inside diameter but its not metal like the original.'m sure there's quite a few things I'm missing but this is what I'm remembering off the top of my head. If you've made it this far, thank you for reading my post in entirety and if (when) I (we) figure out a solution to this issue I will absolutely post in detail. I will try to attach a video that I took while driving if I can figure it out.
Best Regards,
Jameson
​​​

 

Where does the aftermarket temp sensor read from, and does it have its own sensor?

If you aim an IR temperature gun at the engine, does it jump around too?

Engine cold, start engine with radiator cap off. Does a stream of coolant flow into the radiator neck from that cross over tube?

Has the water pump ever been replaced?

 

I will take the temp with my gun tomorrow because the battery is no good. I will also check the crossover tube ( not sure if that's what it's called) to see what's going on there. Should there be coolant flowing into the radiator neck from the tube? The aftermarket temp sender replaced the original sender and screws into the head where the factory sender was. The pump has never been replaced but the one reason I haven't gone that route is because this issue arose only after I replaced my injectors and did all the work I described in my original post. I had no issues before I did the work. I guess this is also why I'm now thinking it's not a head gasket. Thank you for your reply and I will update you in the morning after I check the temp.
Best Regards,
Jameson

 

Have you checked the mechanical fan clutch?

Grab the fan when cold, and try turning it for resistance. Also, check for wobble on the shaft. Check for the same after the engine has reached operating temp.

Had to warranty mine out because it was doing the same thing, and the engine would only cool off when accelerating. It was only 4 months old. It was a Murray. So far replacement has been optimal.

Also, check the condition of the lower radiator hose. Had similar problem. Hose was a year old, but was collapsing when hot. It was weak and spongy feeling and appeared to bulge when hot. It was a Master Pro. Swapped it for a new Gates hose.

Swapped that out and also stopped having temperature swings.

Remember, NEW doesn't mean quality is very good or better than what was installed previously.

Give us a run down on your fan clutch, it's operation and the condition of the lower radiator hose.

 

Hello and thank you for getting back to me. As I stated above in my original message I knew I would forget a few things but let me just add that I did replace my fan clutch and observed my lower radiator hose when it's overheating and no hoses are collapsed. One strange thing I wanted to add too is that when the truck starts to overheat or when the temp starts to come down the blend doors start creaking, making a creaking noise. I only get heat on high because the resistor is bad but other than that I get very hot heat. I just took an infared temperature reading on my hoses and engine components, they are as follows:
● Upper radiator hose 140°F
● Lower radiator hose 115°F
● Block where sender is located 160°F
These reading were taken after driving for half an hour. The whole trip my temperature gauge was jumping from 180°F to 240°F. the first reading I took was when my temp gauge was at 240°F, so the numbers that I wrote here are when my actual temp gauge was reading 240°F. This is what led me to believe in the beginning that it's a head gasket issue with combustion gases displacing the coolant and the temp gauge actually taking a reading of the hot exhaust gases but I could be way off on that and I hope I am. You know how it goes when you're dealing with these issues for so long you start to lose track what you thought it was in the beginning. This is why I came here because my head is so full of ideas of what this could be. I'm not here trying to make it anything other than a head gasket because if it is I'll start tearing it apart but I just don't know. The fact that it didn't start happening until after I pulled the plenum off to replace the fuel injectors is what is keeping me from thinking it's a head gasket because my head gasket can't blow if the truck is sitting in the garage. Thank you for all the advice and ideas , everything hekps, any suggestion,anything. I can't figure out how to post a video here but if anybody has any suggestions of how to do that please let me know and I'll post a video.
Best Regards,
Jameson
​​​​

 

Everything is pointing to a gauge issue. Check the wire to the sender and change that temp sender again.

 

Thats what I'm thinking too. Too much pipe dope or thread sealer on the sender, giving intermittent or variable resistance to ground?

But I have never had the issue myself. Definitely check the fan clutch.

Keep in mind that the PCM uses one temp sensor and the gauges use another.

 

Jameson, we don't mind long posts, we need the info. But please break up the wall of words in the future, it makes it a lot easier to read.

Guys he's seen the same results with two independent gauges now, so it's not a gauge issue. I think there's no other reasonable hypothesis then that gases, combustion gasses or steam are displacing coolant. Things to check...

But first, please next time you get into the thermostat drill a small hole in it. Just a tiny whole in the area around the valve. This helps air escape from under the valve preventing an air pocket that could disrupt the operation of the valve. That said I don't think that's your issue cause it's been so consistent throughout all your parts changes.

1. This may be very rudimentary but the cooling system is under pressure correct? I see no mention of testing or replacing the radiator cap. Something as simple as a bad radiator cap can cause these exact symptoms. Usually there's also a loss of coolant but not always. The radiator cap is a pressure relief valve, and they do fail. You must maintain enough pressure in the coolant when hot to prevent the hot spots inside the block from boiling. If there isn't enough pressure the coolant in the block/heads can boil and create a steam pocket. Usually with a warn radiator cap you lose coolant slowly as well as usually little bits of steam make there way all the way out, but not always. There are testers for radiator caps, but it's really simple to check yourself without the tester, I do it by routine just about every time I open the hood. When it's warmed up try and squeeze the upper radiator hose, you should not be able to squeeze it much at all. If you do it often you'll get a good feel for the temp and hardness and be able to check most of your cooling system with just a squeeze.

All that said even if it looks good, as much as this is costing you, it may be worth while to go grab yourself like a 20lb cap. If increasing the pressure helps at least you learn something and have made progress.

2. Sadly you may have an issue where combustion gasses are leaking into the coolant. BUT don't start pulling it apart, there is a rather easy and cost effective tester to find out. But first there's other clues, mainly gasses in the radiator. If combustion gasses are making there way into the coolant they will make there way to the radiator and this can be noticed. It will appear as if it's always burping air, but in minor leaks this can be hard to notice. So there are testers like this https://www.amazon.com/Lisle-75500-C.../dp/B0007ZDRUI What they do is use a chemical to test for combustion gasses in any gasses that are in the radiator. You put the chemical in the tube like bong water and draw the gasses from the radiator through the chemical. It will change color if there are combustion gasses present.

3. The water pump was mentioned, while no specific reason to suspect the pump. It's easy enough to at least test to find out that it hasn't rotted away or fallen apart on the inside. Remove the radiator cap and rev the engine, the coolant level should rise.

 

Does the temp go up when sitting and down when moving, may be a air problem vs water problem.


That tester BruteFord talked about is awesome and it does work. When I was in the wrenching world I used one all the time.

 

Hello,
thank you so much for your long responses to my issue. I'm sorry that my wording is all broken up but I used the speak to text. I did try to drill a hole in the thermostat a few days ago and it made it worse. There was no coming down from the temperature spike it would just sit there at 230°F until I turned the vehicle off and back on again. my upper radiator hose is definitely firm everytime I turn the vehicle off. I did purchase a new 13 pound radiator cap but with the same result. I will purchase a 20 pound cap tomorrow and let you know how that goes. I also just ordered the tester to see if the combustion gases are entering the cooling system and I'll follow up with you and let you know how that goes. To answer your question plowboy the temperature goes up and down wether im moving or sitting still. One thing that may be coincidence that I've noticed is that the temp doesn't seem to spike nearly as bad when my heater is OFF. Probably coincidence. You've given me some things to check so I'll do that tomorrow and get back to you. Thank you so much.

 

Interesting, could it be that the temperature spikes coincide with the opening of the thermostat? Be easy enough to test, watch the relationship between the temperature of the upper radiator hose and the temp gauge.

 

Definitely a possibility. I will observe tomorrow and get back to you. Thanks again

 

Hello,
Sorry for not getting back to you yesterday but I've been crazy busy. This is going to sound pretty crazy and a lot of this may just be coincidence. Monday night i decided to replace my EGR tube, which I forgot to tell you guys was broken. I had ordered it about a month ago but just hadn't had time to replace it yet. While replacing my EGR tube I noticed that the smog pump was disconnected so I obviously reconnected it. The following morning on my way to the job site, which was about 30 mile trip, I didnt use the heat in my cab and left the **** in the "off" position and I had no issue with the temperature spiking. On my way back home from the job site I left the heat off until I got about two miles from my house then I turned it on "Hi Defrost". Within about a minute-and-a-half my temperature skyrocketed. So today I did the same thing but I drove even further with the same results. I haven't pressure test of the system yet just because I don't have the right tools and I haven't had the time but I will definitely do that this week. I just wanted to let you guys know where I'm at. Could be coincidence I don't know. I will continue to keep you updated. Thank you

 

Ok...here's what I think....

1. You have high electrical resistance in either the sender, or the wire, or somewhere else.
2. Where is the ground for the digital temperature gauge? If it's not a clean, shiny "Block" ground, it's gonna read all over the place.

What it tells me so far is that when you increase electrical load, the temp gauge(s) spike accordingly.

I had a similar problem. The sender on my 300 is located in the Cast iron block. I chased an over temp engine for years...turns out, the rust in the threads wad throwing my temp gauge off.
I also had a digital temperature gauge. The ground was wired to some ground, cant remember where. But when I increased electrical load, it would start to spike, along with the dummy dash gauge. Well, after finally moving the ground to the block and cleaning the threads of the block, (7 years), I finally got my exact temp reading and no more spikes.

Pull the sender from the intake manifold, clean the threads good on both the sender and the intake. Make sure your ground for the digital gauge is bolted to a good block ground. Shiny and bright.

 

Does this truck have air conditioning?

One thing many people forget is that your AC pump turns on when in defrost mode to help dry the air. This will heat the AC condenser.

If so, and if you think maybe the two are related disable your AC by unplugging the AC clutch. It's a two wire plug on the top front of the AC pump.