Burning Smell And Smoke - Cannot Find Cause

[NoahsArk117]

Alright so this is the most confused I've ever been when diagnosing a car problem. Two days ago I noticed a burning smell similar to what you would smell with overheated brakes or a overheated clutch. I would come to a stop light and as soon as I moved again the smell would hit me and then immediately dissappear as soon as I started moving again.

Naturally, I took the car home and immediately began inspecting the engine bay and exhaust for any abnormalities. I don't have a check engine light, all temps look great, driveability hasn't changed one bit, coolant level is steady and color is normal, oil level is good and color is medium to light brown. Engine looks normal, no signs of leaks or melting wire harnesses in sight. So I figured it may have been a piece of debris that got caught on the exhaust and later melted off.

Here is where things get really weird. Today on my way home from work I was doing a few freeway pulls. After I got off the freeway and to the intersection stoplight I noticed smoke coming from the front drivers side of the vehicle as well as the same strong burning smell that you would get with overheated brakes/clutch. I immediately drove to a safe area to pull over and shortly after I came to a stop the smoke stopped. The burning smell was incredibly strong and appeared to be coming from around the brake fluid reservoir. I figured maybe i was frying my clutch so I drove straight home and got to inspecting again.

I pulled into the garage and left the car running with the hood open and tried to pinpoint the location of the smell. This is the part that confuses me by far the most:

- The smell comes and goes every 3-5 minutes regardless of wheather I'm driving or parked.

- I traced the smell to the brake fluid reservoir, the fluid level is correct and the fluid looks normal.

- I left the car to idle for 20 minutes to see if the smell would dissappear but it did not. As mentioned above it comes and goes every 3-5 minutes.

If I was frying my clutch wouldn't I only notice it on heavy pulls? In this case the car can sit for 20 minutes in neutral and still produce the same smell without my driving at all. Aggressive driving seems to increase the intensity of the smell to point where there is visible smoke coming from the driver's side of the engine bay.

I would like to mention that I just had the ckutch replaced a month ago. I put a Exedy Mach 500 kit in and did the standard 750 mile break in period. I'm not sure if this could contribute.

Vehicle is a 16 GT with 70k miles.

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[AceS550]

It’s possible that brake fluid is leaking onto the exhaust manifold causing the smoke/smell. I would have someone hold the clutch pedal down and inspect for leaks.

 

[Mike Pfeifer]

There’s only a few things that will smell like that: brakes (stuck caliper), clutch, motor brushes (starter). I don’t think brake fluid on the manifold will have that distinct odor. Maybe you can get under the car and get your nose right up on the bell housing, if it’s the clutch it should be pretty obvious at that point. If it’s a caliper, you can hover (don’t actually touch) your hand over the wheel on each side and one will feel obviously hotter than the other. I doubt it’s the starter, I have only had one smell like that if there are other symptoms, like an incredibly slow and failed start. Burned control units can smell similar but are a little different - it’s a little “sweeter”. Are there any in the area under or near the brake master cylinder?

 

[I Bleed Ford Blue]

Do you have long tube headers by chance? They sell braided steel clutch lines because the plastic stock line can melt with LTH's and that may be your issue.

 

[NoahsArk117]

There’s only a few things that will smell like that: brakes (stuck caliper), clutch, motor brushes (starter). I don’t think brake fluid on the manifold will have that distinct odor. Maybe you can get under the car and get your nose right up on the bell housing, if it’s the clutch it should be pretty obvious at that point. If it’s a caliper, you can hover (don’t actually touch) your hand over the wheel on each side and one will feel obviously hotter than the other. I doubt it’s the starter, I have only had one smell like that if there are other symptoms, like an incredibly slow and failed start. Burned control units can smell similar but are a little different - it’s a little “sweeter”. Are there any in the area under or near the brake master cylinder?

So I just checked the valve cover bolts and the two near the firewall on the drivers side were finger loose. Just tightened them up and am going to see if that makes a difference. Will update when I gave results.

 

[NoahsArk117]

Do you have long tube headers by chance? They sell braided steel clutch lines because the plastic stock line can melt with LTH's and that may be your issue.

I still have the stock headers on right now, but my cats are starting to smell a little bit more than usual so I'm seeing them in my future so thank you for the tip.

 

[NoahsArk117]

There’s only a few things that will smell like that: brakes (stuck caliper), clutch, motor brushes (starter). I don’t think brake fluid on the manifold will have that distinct odor. Maybe you can get under the car and get your nose right up on the bell housing, if it’s the clutch it should be pretty obvious at that point. If it’s a caliper, you can hover (don’t actually touch) your hand over the wheel on each side and one will feel obviously hotter than the other. I doubt it’s the starter, I have only had one smell like that if there are other symptoms, like an incredibly slow and failed start. Burned control units can smell similar but are a little different - it’s a little “sweeter”. Are there any in the area under or near the brake master cylinder?

So I tightened the loose valve cover bolts and took it for a quick drive. Did quite a few pulls and I didn't smell anything. I'm not saying this is what resolved it but it's one possibility checked off the list for now.

 

[Cobra Jet]

If your valve covers have never been "TSB'd", that's most likely the issue. Ford cheaped out and left off valve cover bolts on the earlier 5.0's and quite a few M6G members had the leaky valve covers early on.

Ford eventually issued a TSB which was to install more bolts.

Here's all you need on that:
Thread containing the valve cover TSB:
https://www.mustang6g.com/forums/threads/valve-cover-leak.131014/#post-2705151

Instructions for L & R valve cover R&R:
https://www.mustang6g.com/forums/attachments/5-0-valve-cover-rh-pdf.401025/

https://www.mustang6g.com/forums/attachments/5-0-valve-cover-lh-pdf.401026/

 

[Shifting_Gears]

Check on the back of the brake reservoir, there is a feed tube to the clutch master cyl I believe. It is inherently not very securely fastened from the factory, so you could have brake fluid seeping out and onto the exhaust.

 

[silverbullet85]

Mine does the same thing, at a stop light I'll randomly smell something burning then see a puff of smoke from under the hood area on the drivers side, then it goes away. I'll check the clutch line and valve cover tomorrow

 

[NoahsArk117]

If your valve covers have never been "TSB'd", that's most likely the issue. Ford cheaped out and left off valve cover bolts on the earlier 5.0's and quite a few M6G members had the leaky valve covers early on.

Ford eventually issued a TSB which was to install more bolts.

Here's all you need on that:
Thread containing the valve cover TSB:
https://www.mustang6g.com/forums/threads/valve-cover-leak.131014/#post-2705151

Instructions for L & R valve cover R&R:
https://www.mustang6g.com/forums/attachments/5-0-valve-cover-rh-pdf.401025/

https://www.mustang6g.com/forums/attachments/5-0-valve-cover-lh-pdf.401026/

Thank you for this, will be heading to the dealer to get this fixed. In the meantime tightening the valve cover bolts seem to help quite a bit.

 

[NoahsArk117]

Mine does the same thing, at a stop light I'll randomly smell something burning then see a puff of smoke from under the hood area on the drivers side, then it goes away. I'll check the clutch line and valve cover tomorrow

I would check your drivers side valve cover bolts. Mine were loose to the point where I was able to turn them with my fingers.

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