I get a rumble through the truck when I stop.
01-29-2018, 11:28 AM
#171
Senior Member
To me it still feels as the truck is about to stall. FORD didn't find a thing wrong with the truck so I'm just going to live with it.
01-29-2018, 02:19 PM
#172
Senior Member
01-29-2018, 02:49 PM
#173
Senior Member
01-29-2018, 09:28 PM
#175
Senior Member
Maybe one of these days a Ford Engineer, or a tech even, will have this solved and may share it with us one day. Hopefully just something to look back on as something we dealt with, not something that became an issue down the road. I try to ignore it for now since it doesn't seem as pronounced nowadays. But, I'm sure I'll "feeling" for it again once summer rolls around.
I like your theory DignifiedDevin. Right now, it seems like the most solid one.
I like your theory DignifiedDevin. Right now, it seems like the most solid one.
01-29-2018, 10:03 PM
#176
Senior Member
Sorry CeeDee,
I got the full report back from the dealer over the last visit, and they decided to replace the fuel tank. This did not fix the problem but the rumble is also not as bad. It's now much harder for me to replicate the issue as well. The problem now is, I don't know if it was the fuel tank, or something else like maybe something was loose that the mechanic may have tightened when installing the new tank.
So my newest possible theory is with the design of the fuel tank. There is a front "pocket" in the tank (which I marked with the arrow in the picture provided) and from all I've seen in pictures, there is no vent line back to the main section of the tank to give relief when fuel is fills that area and is then removed. Most old tanks that had a pocket like this had vent lines to not cause a vacuum effect. Now under normal conditions I can see that with such a small pocket there would be no need for a vent line, but because this only happens when I come to a stop and only when fuel is 3/4 full, I can see this creating a vacuum and forcing air to push by the fuel to fill that void. That air forcing itself back would create that same turbulence effect you get when you flip a quart of oil over to quickly.
Kinda makes sense no?
I got the full report back from the dealer over the last visit, and they decided to replace the fuel tank. This did not fix the problem but the rumble is also not as bad. It's now much harder for me to replicate the issue as well. The problem now is, I don't know if it was the fuel tank, or something else like maybe something was loose that the mechanic may have tightened when installing the new tank.
So my newest possible theory is with the design of the fuel tank. There is a front "pocket" in the tank (which I marked with the arrow in the picture provided) and from all I've seen in pictures, there is no vent line back to the main section of the tank to give relief when fuel is fills that area and is then removed. Most old tanks that had a pocket like this had vent lines to not cause a vacuum effect. Now under normal conditions I can see that with such a small pocket there would be no need for a vent line, but because this only happens when I come to a stop and only when fuel is 3/4 full, I can see this creating a vacuum and forcing air to push by the fuel to fill that void. That air forcing itself back would create that same turbulence effect you get when you flip a quart of oil over to quickly.
Kinda makes sense no?
01-29-2018, 11:26 PM
#177
Dignified Member
Thread Starter
NoI'm suggesting in theory that it is possible that the tank design is flawed. I along with all the Ford mechanics have agreed that the sound and vibration that is made, does not come from normal fuel slosh.
Have you ever taken a quart of oil and flipped it over quickly? there is a suction or vacuum effect when this happens. the plastic quart looks like its breathing in and out rapidly. the container is fighting atmospheric pressure, a little air gets in and the container expands, a little oil comes out and the container contracts. I believe that this might be happening in the fuel tank where there is no vent relief.
Its a simple check by Ford.
Find a truck that has this issue, drop the tank, install a vent line from the front of the tank to the center of the tank, and see if it still does it.
01-30-2018, 10:09 AM
#178
Senior Member
Truck details in sig....
I don't know if this is related or not. I've always felt the brake to gas "clunk" that feels like a sloppy drive line. Recently, I've come to notice a sound that I would say is coming from the rear. I don't feel it as a shudder, but I could see the progression of it becoming one. I'm late to this thread, so hang with me.
1) Fuel tank slosh. I think in the diagram you're seeing the molded wells that give structural rigidity to the the plastic tank. I also don't think it could be fuel slosh. It just wouldn't oscillate that fast. But the vent theory is interesting. If the thank has pressure and it opens/closes quickly it could cause a drum like vibration in the tank. After all, the tank is plastic. Then it could cause a pressure feedback. Valve open and the pressure drops, valve closes, pressure spikes, valve opens, and repeat.....(think of ripping a fart). If this were true, it wouldn't happen on a completely full tank. As for the vacuum effect, I think it would be one big bump and not a shudder. Think about it. A 5 gallon fuel can doesn't dance around like it's possessed in the bed of your truck every time you stop. But stress relieving on the tank straps could be translating back through the chassis.
2) My problem is more sound. There's a few things going on. To describe it, when you're completely stopped, you can slowly let off the brakes and you can get a sound from the brakes that they're sticking and skipping on the rotors. That's the same kind of sound this is, coming to a stop is a slower oscillation and more magnified. With what others are describing, I wonder if this isn't just the first symptoms.
3) I do have an observation that I think is valuable to this thread. In trying to diagnose my issue, I had the radio off and watched my dash as I came to a stop at different pressures/speeds. Everyone drives different, so I'll say it happens the most at my "normal" stop. My RPMs never changed. But as I came to a stop, my transmission was in 3rd and as soon as I was stopped it changed to 1st. Right as that happened is when I heard my sound. If I had to guess, it's that drive line slop. For the sake of describing it, I'll say positive and negative load. When you're on the gas, the drive line is positive loaded. Engine braking negative loading. When I come to a stop, and it does the 3rd to 1st shift, it sounds like it's bouncing 2-4 times between positive and neutral loading. Basically a third of the normal slop clunk, and rapidly. I'm going to try a manual shift down to 1st before I'm stopped. What's difficult for me is trying to stop normally when I'm trying to recreate. That manual shift might not be the only conditional.
4) Greasing the slip yolk. What about drilling it and putting a zerk in?
I don't know if this is related or not. I've always felt the brake to gas "clunk" that feels like a sloppy drive line. Recently, I've come to notice a sound that I would say is coming from the rear. I don't feel it as a shudder, but I could see the progression of it becoming one. I'm late to this thread, so hang with me.
1) Fuel tank slosh. I think in the diagram you're seeing the molded wells that give structural rigidity to the the plastic tank. I also don't think it could be fuel slosh. It just wouldn't oscillate that fast. But the vent theory is interesting. If the thank has pressure and it opens/closes quickly it could cause a drum like vibration in the tank. After all, the tank is plastic. Then it could cause a pressure feedback. Valve open and the pressure drops, valve closes, pressure spikes, valve opens, and repeat.....(think of ripping a fart). If this were true, it wouldn't happen on a completely full tank. As for the vacuum effect, I think it would be one big bump and not a shudder. Think about it. A 5 gallon fuel can doesn't dance around like it's possessed in the bed of your truck every time you stop. But stress relieving on the tank straps could be translating back through the chassis.
2) My problem is more sound. There's a few things going on. To describe it, when you're completely stopped, you can slowly let off the brakes and you can get a sound from the brakes that they're sticking and skipping on the rotors. That's the same kind of sound this is, coming to a stop is a slower oscillation and more magnified. With what others are describing, I wonder if this isn't just the first symptoms.
3) I do have an observation that I think is valuable to this thread. In trying to diagnose my issue, I had the radio off and watched my dash as I came to a stop at different pressures/speeds. Everyone drives different, so I'll say it happens the most at my "normal" stop. My RPMs never changed. But as I came to a stop, my transmission was in 3rd and as soon as I was stopped it changed to 1st. Right as that happened is when I heard my sound. If I had to guess, it's that drive line slop. For the sake of describing it, I'll say positive and negative load. When you're on the gas, the drive line is positive loaded. Engine braking negative loading. When I come to a stop, and it does the 3rd to 1st shift, it sounds like it's bouncing 2-4 times between positive and neutral loading. Basically a third of the normal slop clunk, and rapidly. I'm going to try a manual shift down to 1st before I'm stopped. What's difficult for me is trying to stop normally when I'm trying to recreate. That manual shift might not be the only conditional.
4) Greasing the slip yolk. What about drilling it and putting a zerk in?
Last edited by TheGeek; 01-30-2018 at 10:11 AM.
01-30-2018, 12:46 PM
#179
Amazing after 18 pages of describing fuel slosh, no one thinks thats it. Fuel slosh doesnt have to just be the truck rocking back and forth. After stopping the fuel may move back and forth heavily once or twice. It would take a second to happen, probably happen once, and stop, only happen above a certain fuel level, goes away when stopping very slowly. Which is exactly what you guys are describing. And with the odd geometry of the tank, it could easily bounce off surfaces and cause a shutter feeling. You guys see that this is all describing the motion of fuel with inertia in a tank right?
01-30-2018, 01:09 PM
#180
Dignified Member
Thread Starter
Amazing after 18 pages of describing fuel slosh, no one thinks thats it. Fuel slosh doesnt have to just be the truck rocking back and forth. After stopping the fuel may move back and forth heavily once or twice. It would take a second to happen, probably happen once, and stop, only happen above a certain fuel level, goes away when stopping very slowly. Which is exactly what you guys are describing. And with the odd geometry of the tank, it could easily bounce off surfaces and cause a shutter feeling. You guys see that this is all describing the motion of fuel with inertia in a tank right?