Clunking sound after auto stop??

Danny Ramirez

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i hear and feel a clunking/ thump sound on the brake pedal whenever the engine auto-stops. Sometimes, I hear and feel this randomly when driving at slower speeds, or noteably when i stop at the top of my drive way to turn around in the morning.. I cant really pinpoint exactly what causes it. I am fairly certain it is NOT related to the suspension, since it seems to happen alot whenever i am fully stopped.

The best way i can describe it:: imagine if there was a one foot long piece of pipe with caps on both ends and a big metal ball bearing on the inside.. and it was strapped to the body of the truck right underneath the driver side floor pan. It is not really a hard thud or anything truly concerning, but is definately noticeable.

Again.. weight shift or road obstacle do not trigger it... it seems like something within the braking system.

Any ideas?

Thanks.

2019 Ranger STX FX4
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P. A. Schilke

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i hear and feel a clunking/ thump sound on the brake pedal whenever the engine auto-stops. Sometimes, I hear and feel this randomly when driving at slower speeds, or noteably when i stop at the top of my drive way to turn around in the morning.. I cant really pinpoint exactly what causes it. I am fairly certain it is NOT related to the suspension, since it seems to happen alot whenever i am fully stopped.

The best way i can describe it:: imagine if there was a one foot long piece of pipe with caps on both ends and a big metal ball bearing on the inside.. and it was strapped to the body of the truck right underneath the driver side floor pan. It is not really a hard thud or anything truly concerning, but is definately noticeable.

Again.. weight shift or road obstacle do not trigger it... it seems like something within the braking system.

Any ideas?

Thanks.

2019 Ranger STX FX4
Hi Danny,

I have read your post several times and do not understand what you are trying to say. I would like to help if possible, but need a more clearer understanding. My first thought is that the driveshaft slip splines are in a stick/slip and what you feel ias you stop is the splines stick and then slip abruptly, causing the clunk. This should be taken to the dealer and have it investigated, but removal of the driveshaft and lubing the slip yolk might help.

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired
 
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Danny Ramirez

Danny Ramirez

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Hi Danny,

I have read your post several times and do not understand what you are trying to say. I would like to help if possible, but need a more clearer understanding. My first thought is that the driveshaft slip splines are in a stick/slip and what you feel ias you stop is the splines stick and then slip abruptly, causing the clunk. This should be taken to the dealer and have it investigated, but removal of the driveshaft and lubing the slip yolk might help.

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired
Thanks for your help. It is actually a little hard to explain. I personally do not think it has anything to do with the main drive shaft, because i imagine if it slipped the way you explained, I would likely feel a thump in the rear end as well.

To me, this feels like something that happens automatically behind the firewall once auto-stop is engaged. Again, it doesnt only happen when the engine turns off, it happens sometimes when driving at low speeds. I just know that it will happen 100% of the time when the engine turns off with auto-stop.

I just want to stress that it most likely does not have anything to do with the suspension, because it happens when the truck is at a stand still.

My two best guesses are; 1. A component of the 4x4 system is slipping/shifting or 2. A compenent of the actaul brake pedal system is shifting once the truck stops.

I feel it in the brake pedal because it only happens when im dirivng slow or when i am stopped... my foot is always on the brake durring these situations. If i had to pin point the sound, I would sa right behind the firewall on the driver side.
 

P. A. Schilke

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Thanks for your help. It is actually a little hard to explain. I personally do not think it has anything to do with the main drive shaft, because i imagine if it slipped the way you explained, I would likely feel a thump in the rear end as well.

To me, this feels like something that happens automatically behind the firewall once auto-stop is engaged. Again, it doesnt only happen when the engine turns off, it happens sometimes when driving at low speeds. I just know that it will happen 100% of the time when the engine turns off with auto-stop.

I just want to stress that it most likely does not have anything to do with the suspension, because it happens when the truck is at a stand still.

My two best guesses are; 1. A component of the 4x4 system is slipping/shifting or 2. A compenent of the actaul brake pedal system is shifting once the truck stops.

I feel it in the brake pedal because it only happens when im dirivng slow or when i am stopped... my foot is always on the brake durring these situations. If i had to pin point the sound, I would sa right behind the firewall on the driver side.
Hi Danny,

If you can reproduce 100% of the time when auto stop is enabled, this should help track it down ,and the location as you described should help as well. I think the dealer service people need to be involved. You might be able to try this with another person in a deserted parking lot, have an observer standing there to the side of the vehicle with the hood open, Back the vehicle up and drive forward and time the stop when he/she is next to the open engine compartment. See if the observer hears the noise and an idea of direction. This is all done at a very slow speed!

Also, can you hold the brake down and set the parking brake too, and engage the transmission and rev the motor, then let up on the accelerator pedal abruptly. Does it clunk? Then try the same thing in reverse. Clunk? Have an observer listening with the hood open. If it is a loose attachment or if the engine moves excessively (loose engine mount?). Then try Reverse to Drive with the brakes applied...Clunk then. All this is done with the vehicle static.

All the above are things we do to find problems when in the field. In all cases, make sure the observer has his/her feet away from the tires, just in case.

Interesting Diagnostic...

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired
 

Skylais

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i hear and feel a clunking/ thump sound on the brake pedal whenever the engine auto-stops. Sometimes, I hear and feel this randomly when driving at slower speeds, or noteably when i stop at the top of my drive way to turn around in the morning.. I cant really pinpoint exactly what causes it. I am fairly certain it is NOT related to the suspension, since it seems to happen alot whenever i am fully stopped.

The best way i can describe it:: imagine if there was a one foot long piece of pipe with caps on both ends and a big metal ball bearing on the inside.. and it was strapped to the body of the truck right underneath the driver side floor pan. It is not really a hard thud or anything truly concerning, but is definately noticeable.

Again.. weight shift or road obstacle do not trigger it... it seems like something within the braking system.

Any ideas?

Thanks.

2019 Ranger STX FX4
I think i know what your talking about.. I have a similar thud and release of pressure on the brake system when auto-shut off occurs, but it all feels normal to me. I just assumed that its part of the the mechanics shutting off. I just assumed the thud was just the engine knocking off temporarily and the brake system. Don't ever feel at at any speed above idle though.
 


THLONE

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I bet you are using your left foot on the brake and right on the gas.
 

oubbascooba

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Mine does this as well. I bet it is part of the air circulation system moving the vents under the dash, as it lowers the blower etc. Happens to mine every stop as well. Brakes depresses slightly, and feel a small *clunk*. And no THLONE, i don't drive with two feet. I'll experiment today with my air system off and see if the clunk happens.
 

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After my time in the truck, I think it's

A). The engine rocking back/forth from compression after coming to a stop, or

B). ABS/Brakes locking in the braking force due to engine vacuum going away
 

calistangr

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I have beem having the same issue myself... when I accelerate from a stop or come to a quick stop it feels the motor mounts are loose.
 

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i hear and feel a clunking/ thump sound on the brake pedal whenever the engine auto-stops. Sometimes, I hear and feel this randomly when driving at slower speeds, or noteably when i stop at the top of my drive way to turn around in the morning.. I cant really pinpoint exactly what causes it. I am fairly certain it is NOT related to the suspension, since it seems to happen alot whenever i am fully stopped.

The best way i can describe it:: imagine if there was a one foot long piece of pipe with caps on both ends and a big metal ball bearing on the inside.. and it was strapped to the body of the truck right underneath the driver side floor pan. It is not really a hard thud or anything truly concerning, but is definately noticeable.

Again.. weight shift or road obstacle do not trigger it... it seems like something within the braking system.

Any ideas?

Thanks.

2019 Ranger STX FX4
Did you figure out what the cause was, im experiencing the same thing
 

Porpoise Hork

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@Danny Ramirez it sounds an awful lot like the splines on the slip yoke for the driveshaft are binding up and then releasing. This is a known issue with Ford's 2-piece driveshafts. Then the shaft splines bind up and then release it makes a very noticeable clunk much the same way as you describe. It's an easy fix and the dealer should take care of it under warranty. If this is the issue, the rubber dust boot on the drive shaft after the center bearing will need to be removed and the splines lubricated with PTFE lubricant and a new boot and clamp installed. If it's not under warranty you can buy the boot and clamp kit and do it yourself, but it does require a special clamp tool.
 
 



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