MGExp

MG Midget Forum

Mid - high rpm rattle / grinding noise

Moss Motors
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor

Topic List Forum List Newer Older Start New Topic
Mid - high rpm rattle / grinding noise
#1
kurtk Kurt K
Flanders, NJ, USA   USA
Sign in to contact
1973 MG Midget MkIII
72 midget, has a rattle/grinding noise that kicks in at 3500rpm. Video linked:

https://youtube.com/shorts/Z1qLKy6cBQA?si=8_WyZBbCq1C1zHrx

Does this sound like something mechanical? (Excess valve play, bearings, not enough advance, etc) I have done a full tune up. It runs great, just this noise I’m worried about causing damage as I am unable to locate any externally vibrating elements.

Reply
Was this post helpful or interesting?
Yes No Thank
. Become a Supporting Member to hide this ad & support a small business
Re: Mid - high rpm rattle / grinding noise
#2
Wellkevi01 Avatar
Wellkevi01 Gold Member Kevin Wells
Midland, MI, USA   USA
Sign in to contact
1978 MG Midget MkIV
Kinda hard to tell from the video, but could it be an exhaust leak? It seems to stop right when you clutch in and the load on the engine subsides while you shift. It then seems to come back when you release the clutch and continue accelerating.

And it sounds like you have straight cut gears in the gearbox?

Reply
Was this post helpful or interesting?
Yes No Thank
Re: Mid - high rpm rattle / grinding noise
#3
AN5L8016 Avatar
AN5L8016 Mark Haynes
Nederland, CO, USA   USA
Sign in to contact
1958 Austin-Healey Bugeye Sprite "Bertie"
If it disappears when you depress the clutch, then you may have a loose throw-out bearing rattling on the pressure plate


'58 Bugeye
'05 Mini Cooper S

Reply
Was this post helpful or interesting?
Yes No Thank
. Become a Supporting Member to hide this ad & support a small business
Re: Mid - high rpm rattle / grinding noise
#4
gg71 Silver Member Greg Grohoski
Austin, TX, USA   USA
Sign in to contact
1973 MG Midget
I must be going deaf, but I don't hear any rattle.

The gear whine is normal for the ribcase transmissions.

Reply
Was this post helpful or interesting?
Yes No Thank
  LorenFL thanked gg71 for this post
Re: Mid - high rpm rattle / grinding noise
#5
refisk Rick Fisk
Frankenmuth, MI, USA   USA
Sign in to contact
Same here, I couldn't hear anything unusual. But I have 75 year old ears. lol

In reply to # 4789053 by gg71 I must be going deaf, but I don't hear any rattle.

The gear whine is normal for the ribcase transmissions.

Reply
Was this post helpful or interesting?
Yes No Thank
Re: Mid - high rpm rattle / grinding noise
#6
kurtk Kurt K
Flanders, NJ, USA   USA
Sign in to contact
1973 MG Midget MkIII
Could be, i'll take a look. I had an exhaust leak on another car a few years back and it was noticeable through the entire rpm range. This noise only starts at 3500 rpm. I'm aware of the first gear whine, that's not what I'm referring to (I think)

In reply to # 4789018 by Wellkevi01 Kinda hard to tell from the video, but could it be an exhaust leak? It seems to stop right when you clutch in and the load on the engine subsides while you shift. It then seems to come back when you release the clutch and continue accelerating.

And it sounds like you have straight cut gears in the gearbox?

The noise is there regardless of clutch pressed or not. It does get a bit quieter under less load (coasting) but it's still there.

In reply to a post by AN5L8016 If it disappears when you depress the clutch, then you may have a loose throw-out bearing rattling on the pressure plate

Definitely harder to hear on film than in person. If you listen closely, as soon as that tachometer hits 3500 rpm the noise kicks in. It's a high pitched rattle/grinding noise.

Reply
Was this post helpful or interesting?
Yes No Thank
Re: Mid - high rpm rattle / grinding noise
#7
robjohn Bob Johnson
Sacramento, CA, USA   USA
Sign in to contact
1971 MG Midget MkIII "The Red Car"
Kurt,
Since it appears the RPM is the common factor, you may want to look at the body frame clearance of the vertical part of the exhaust pipe where it make the 90 degree turn to head back under the car. There may be a harmonic vibration at that exact RPM that will make it vibrate against the frame. It may be you have a weak/broken motor mount which is why it seems to change under load.

Bob

'71 Midget


"For those who have defended it; FREEDOM has a meaning the protected will never understand."



Edited 1 time(s). Last edit at 2024-04-26 10:38 AM by robjohn.

Reply
Was this post helpful or interesting?
Yes No Thank
Re: Mid - high rpm rattle / grinding noise
#8
Bluey Avatar
Bluey Paul Crombach
LEIDSCHENDAM, Netherlands   NLD
Sign in to contact
1964 MG Midget MkII
Could also be the gearstick anti rattle.
Have you tried gently holding the gearstick to see if the noise goes away? (btw don't do this as a permanent solution as you will wear gearbox internals).
Could be the anti rattle parts in your gearshift assembly are worn.

Reply
Was this post helpful or interesting?
Yes No Thank
Re: Mid - high rpm rattle / grinding noise
#9
kurtk Kurt K
Flanders, NJ, USA   USA
Sign in to contact
1973 MG Midget MkIII
Here is another look at the rattle. Definitely some vibration coming from the engine. when I hold the air filters, I can feel it vibrate when this noise kicks in.

https://youtube.com/shorts/JZtMWXBbevw?si=Wg9ppOq_3lIBq8Hm

The exhaust is not hitting the frame where it turns 90, and I tried holding the shift nob, no change. Like I said now that I looked at it in the engine, definitely something vibrating in there.

I can't located the exact spot of the noise, what would be the first thing to wear that could cause this vibration? Only 27k miles. Potentially a timing issue? I only checked static timing.

Reply
Was this post helpful or interesting?
Yes No Thank
Re: Mid - high rpm rattle / grinding noise
#10
gg71 Silver Member Greg Grohoski
Austin, TX, USA   USA
Sign in to contact
1973 MG Midget
So it seems more like a knock than a rattle to me, if that’s the noise you’re referring to.

Reply
Was this post helpful or interesting?
Yes No Thank
Re: Mid - high rpm rattle / grinding noise
#11
westfield7 Michael Wooten
Greenville, SC, USA   USA
Sign in to contact
1983 Westfield Seven "Green Car"
The dipstick seems to rise out of its “home”. Could it be rattling against the oil feed pipe?

Reply
Was this post helpful or interesting?
Yes No Thank
Re: Mid - high rpm rattle / grinding noise
#12
SJC Avatar
SJC Stuart Cole
Dorking, Surrey, UK   GBR
Sign in to contact
1970 MG Midget
How about getting a friend to work the accelerator whilst you listen at the end of a long screwdriver to points on the block/head? take care to stay away from anything moving, but should at least identify the area of the noise.
Have you considered the engine/gearbox mounts ?
Stuart

Reply
Was this post helpful or interesting?
Yes No Thank
Topic List Forum List Newer Older Start New Topic

To reply or ask your own question:

or

Registration is FREE and takes less than a minute

Forums  

Having trouble posting or changing forum settings?
Read the Forum Help (FAQ) or contact the webmaster





Join The Club
Sign in to ask questions, share photos, and access all website features
Forum List
MGB & GT MG Midget Buy, Sell & Trade Vendor Market MG Performance MG Engine Swaps Factory Correct MGA MGC MG Magnette 1100 & 1300 T-Series & Prewar EV Conversion Modern MG MG Motorsports Events & Meetup MG 2024 Katy Texas Other Vehicles Off Topic Clubs Archived
Your Cars
1979 MG MGB
Chris B   USA
1979 MGB
Text Size
Larger Smaller
Reset Save