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#1
  This topic is about my 1968 MG MGC GT
jsrivard Avatar
jsrivard Silver Member Joel Rivard
Ramstein, Rheinland-Pfalz, Germany   DEU
1968 MG MGC GT "Maggie"
Well, you take a 49year old car on a 1094 mile journey averaging 65mph on the highway and your bound to run into problems, right? On the bright side I did average ~28mpg on the highway. Sorry in advance for the long post...

For those in attendance my car was the one up on jacks being serviced by the fine fellows from the RAC, thanks to them for that, and to Mick for informing me on their vast range of services (see picture below).

1. The reason for the RAC help.... I'm getting air in my brake lines somehow. I believe it is either the master cylinder is faulty or the brake line fitting coming out of the master is letting air in. When I pump the brake pedal and release it I can see tiny air bubbles coming up from the bottom of the reservoir. Over the 500mi one way trip, the level in the reservoir increased until when I got to the event it was overflowing. To me, this says that air is getting in but no fluid is leaking out so the air is displacing fluid in the lines and causing the reservoir to back up but I can not see anything leaking out anywhere. The RAC guys bled the brakes and it was working well afterward but on the journey home the same thing happened and the brakes got progressively spongier (is that a word?). I tried to tighten up the line fitting on the MC and got a 16th of a turn out of it. I'll try to bleed the brakes again and see if that sorted it. Otherwise I think I'm at the replace the MC step. I think I'm there anyway as I have to dismantle the entire thing to work out the bubbling paint issue I now have below the MC.

2. When I accelerate hard and the RPM's get up ~over 3k there is a clattering noise from the shift lever. Sounds like a washer or something metal is lose where the shifter meets the transmission. I've tried to take the boot off and look in there for anything obvious but nothing stood out. Anyone else hear of this/know what it is?

3. My speedo stopped working about half way through the trip. It has always kind of jumped around but now it hangs at about 10mph and goes no further. The odometer works normally. If I knock on the face with my hand the speedo will jump up about 5mph at a time until it is reading the actual speed but then it will get stuck again. Is this the cable or a bad gauge? Do the odometer and speedo work off different cables?

4. Is it normal for there to be a bit of torque steer with the MGC? When cruising on the highway and push the throttle down, she tends to pull right and then when I let off I need to steer a bit right to counter the tenancy to drift back to the left. It's not drastic but noticeable I've driven FWD cars that were much worse.

Thanks all, the event was excellent and I am very glad I made the trip. Wish I could have been there all 4 days.



Cheers,
Joel

MGC Life Blog: https://mgc.is-great.net/
MGC "how-to's" available on YouTube: https://www.youtube.com/channel/UCDMf5tRcUOG0ueyizruhv5w/

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J Baz Avatar
J Baz Silver Member Jerard Basmagy
Middletown, New Jersey, USA   USA
4. Is it normal for there to be a bit of torque steer with the MGC? When cruising on the highway and push the throttle down, she tends to pull right and then when I let off I need to steer a bit right to counter the tenancy to drift back to the left. It's not drastic but noticeable I've driven FWD cars that were much worse.

Since B's and C's share the same rear suspension set up I recommend you check the rear spring u-bolts and pads. I experience the same effect with a B once, it pulled to the right on hard acceleration then back to the left when I released the gas. I found that the U bolts were loose after a rebuild. Once I tightened them up the torque steer went away.

Best of luck sorting things out.



jb

Too soon we get old, too late we get smart!



Edited 1 time(s). Last edit at 2017-06-14 04:11 AM by J Baz.

jsrivard Avatar
jsrivard Silver Member Joel Rivard
Ramstein, Rheinland-Pfalz, Germany   DEU
1968 MG MGC GT "Maggie"
Thanks Jerard, I'll take a closer look at the nuts on there. I did just rebuild the rear suspension. I installed with nylock nuts. The shop manual specifies one nut to tighten the u-bolts and another to lock that nut in place which should be flush at the bottom with the bolt. I just tightened the nylock nuts enough so that another nut would fit on the exposed bit of bolt but didn't measure anything and there is no prescribed torque spec that I could find. I could tighten them more but I feel that would just serve to compress the poly spring pads. The nylock nuts have not backed off any that I can tell but I'll check again.



Cheers,
Joel

MGC Life Blog: https://mgc.is-great.net/
MGC "how-to's" available on YouTube: https://www.youtube.com/channel/UCDMf5tRcUOG0ueyizruhv5w/

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J Baz Avatar
J Baz Silver Member Jerard Basmagy
Middletown, New Jersey, USA   USA
Let me know if it helps.
jb



jb

Too soon we get old, too late we get smart!

PFT-000 Bruce Ibbotson
Brisbane, Australia   AUS
1968 MG MGC GT "The Truck"
1968 MG MGC GT "The Truck"
Joel,

The gear lever rattle in the MGC gearbox seems to be a common problem when under full power, this is very annoying in third gear. I decided it was gear lever resonance after I fitted a nice UK made leather gear knob. At 6,000 rpm in 3rd there was a very loud bang. I shut down and after stopping found the shattered remains of the new gear knob all over the passenger seat. This proved my assumption and I decided to raise the resonant frequency of the lever by shortening it, after which the lever was quiet under all conditions. When I find the photos & procedure I will post them.

A friend in the UK had the exact same problem with his MGC and followed my idea to find the lever was quiet after he did this simple modification. My box is quiet under all conditions the lever throw is shorter so the shift is a little stiffer.

Bruce.

PFT-000 Bruce Ibbotson
Brisbane, Australia   AUS
1968 MG MGC GT "The Truck"
1968 MG MGC GT "The Truck"
Joel,

I cannot locate the article in PDF format, I did find an email with photos which I don't know how to put on this Forum so I have emailed the email with 2 photos directly to you. In my car I have a 1972/3 MGB centre console and I put the vinyl cover over the rubber boot and this vinyl cover sits just under the bottom of the gear knob. I cannot find this photo either, I am having a very BAD computer day. I hate computers.

Bruce.

jsrivard Avatar
jsrivard Silver Member Joel Rivard
Ramstein, Rheinland-Pfalz, Germany   DEU
1968 MG MGC GT "Maggie"
Bruce, Thanks, I received your email. It doesn't only happen under full throttle but really anything over 1/2 throttle acceleration. Here's a video of the sound to see if it is the same thing you are describing.





Cheers,
Joel

MGC Life Blog: https://mgc.is-great.net/
MGC "how-to's" available on YouTube: https://www.youtube.com/channel/UCDMf5tRcUOG0ueyizruhv5w/

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jsrivard Avatar
jsrivard Silver Member Joel Rivard
Ramstein, Rheinland-Pfalz, Germany   DEU
1968 MG MGC GT "Maggie"
And here's a video of the speedometer problem. Hopefully someone recognized this from experience so I can avoid hunting and pecking at solutions. Thanks all.





Cheers,
Joel

MGC Life Blog: https://mgc.is-great.net/
MGC "how-to's" available on YouTube: https://www.youtube.com/channel/UCDMf5tRcUOG0ueyizruhv5w/

PFT-000 Bruce Ibbotson
Brisbane, Australia   AUS
1968 MG MGC GT "The Truck"
1968 MG MGC GT "The Truck"
Joel,

That is not nearly as bad as in my car or Bill's MGC in the UK. From memory I never noticed the rattle until I fully insulated the car for Air Conditioning. In our Sub Tropical climate all windows were fully open almost all the time which would have masked the rattle. It was the exploded gear knob that brought it to attention. I ended up with the threaded shaft and the nasty chrome nut with sharp chrome dags on the hexagon. I had to wrap a handkerchief around the lever to drive home and refit the factory knob.

You could try pushing a 75 mm piece of 12.7 mm ID trailer vacuum hose down the shaft, to reduce the vibrations, later MGB gear levers had a rubber coupled lever because of this problem, if you can find one it would fix it. All modern cars have this rubber coupled arrangement for the gear lever. I think general wear in the gear selector linkages makes this resonance obvious, even replacing the Nylon split bushes does not help.

Bruce.

PFT-000 Bruce Ibbotson
Brisbane, Australia   AUS
1968 MG MGC GT "The Truck"
1968 MG MGC GT "The Truck"
Joel,

I have given up trying to find the article I wrote about this problem so I will start again here for Forum readers:

The gear lever (shift lever) rattle in 3rd and other gears under power is caused by resonance periods in the lever or harmonics of the main resonance. To raise the resonant frequency I simply cut 7/8" (.875"winking smiley of the threaded section off (soft steel), then after checking the depth of thread in the Black Spherical knob drilled out the knob 1/64" bit at a time until I could screw the knob down to cover the chrome section completely hiding the non plated ugly threaded section. I pushed a piece of trailer vacuum hose (very thick walls with robust construction) 3" (75 mm) long by 1/2" (12,7 mm ID) fully down the lever to just clear the mounting plate and fit inside the rubber boot. To secure the knob I wound PTFE tape around the thread (as a plumber does with fittings) and refitted the knob. This worked a treat. No noise or rattle at all in any gear at any power. The knob does not move in use with the PTFE tape wound around the thread, don't over do it.

Photos attached.

Bruce.


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PFT-000 Bruce Ibbotson
Brisbane, Australia   AUS
1968 MG MGC GT "The Truck"
1968 MG MGC GT "The Truck"
Joel,

The problem is in the Speedo head itself, I had my Speedo rebuilt years ago because of a + & - 10 mph variation around the correct reading. The shaft was found to be slightly bent causing binding and the Speedo had to be remagnitised and calibrated. This reduced the fluctuations to + & - 2 mph around the correct reading at lower speeds it read constant readings above 60 mph. The Speedo Cable was the main cause of this.

I fitted a replacement cable (made in Germany) and the Speed reading settled down, do NOT lubricate the inner spiral cable.
The cable inner rusts and fills up with crud over time lubricating it actually makes it worse. It was explained to me that the inner cable works like a long thin torsion bar and over time the strands start to act like a spring with a new cable required to solve the problem.


There is not much on my car that I have not had to dismantle and fix over the decades, An MGC/GT is a work in progress retirement hobby for us who do all their own repairs.

Bruce.

Tim Moore Avatar
Scotland, UK   GBR
1947 Rover 16 "Reggie"
1969 MG MGC GT
Joel,

Saw you all at Chateau Impney, like us you drove a huge round trip to be there, indeed well worth the effort.

Specifically on your speedometer,

Trip meter and speedo work off same drive cable.

Have never stripped an MGA B or C speedo gauge but...had a similar issue with a jaeger gauge on our 1947 Rover 16 years ago. Problem was small mirror face inside gauge which interprets cable revolutions was oily and causing intermittent or sticking needle. Cleaning this mirror carefully, with lint free cloth and a little white spirit solved my problem....The drive cable can emit oil over the years into the inside back face of the speedometer.

So suggest if no one knows otherwise you remove gauge remove glass face and rear cover to see if similar exists within.

Gauges are relatively easy to locate from suppliers or ebay as you know so if any significant issue in yours prevents repair.

The C even though you had those four issues during your epic, the brakes being the most worrying, did you proud. Well done.

Tim

jsrivard Avatar
jsrivard Silver Member Joel Rivard
Ramstein, Rheinland-Pfalz, Germany   DEU
1968 MG MGC GT "Maggie"
So Bruce, if I understand you correct I need a new Speedo gauge or rebuild but also need (or at least should) replace the cable since I'm taking it apart, which will eliminate/limit the oscillations? I've seen Nisonger recommended on here before for rebuild, I'm guessing they are a good place to send it?

Thanks so much.



Cheers,
Joel

MGC Life Blog: https://mgc.is-great.net/
MGC "how-to's" available on YouTube: https://www.youtube.com/channel/UCDMf5tRcUOG0ueyizruhv5w/

jsrivard Avatar
jsrivard Silver Member Joel Rivard
Ramstein, Rheinland-Pfalz, Germany   DEU
1968 MG MGC GT "Maggie"
Tim, thanks for the info on the speedo. To be fair to the old girl, the speedo was a bit dodgy prior to the trip as was the shift lever rattle. It's just you have a lot of time to stare at the imperfections on a long drive such as this and now I have renewed energy (especially seeing all the fine examples at the event) to make her perfect whereas before I was willing to live with the little niggles to keep her on the road.



Cheers,
Joel

MGC Life Blog: https://mgc.is-great.net/
MGC "how-to's" available on YouTube: https://www.youtube.com/channel/UCDMf5tRcUOG0ueyizruhv5w/

PFT-000 Bruce Ibbotson
Brisbane, Australia   AUS
1968 MG MGC GT "The Truck"
1968 MG MGC GT "The Truck"
Joel,

The Smith's Speedo is a primitive instrument (El-Cheapo) totally unlike the quality Jaeger Unit used on high end cars.

I would send the Speedo head to some well known established Instrument Repairer and I would certainly replace the cable, Tim is correct oil and muck travel up the cable over time and get into the Speedo head starting the problems with fluctuations and incorrect readings. Time is not on the side of Smith's Tacho's & Speedo's. I have had both of these rebuilt and calibrated. In my Tacho I replaced the cheap & archaic open element potentiometer with a high quality minature potentiometer [from a Broadcast Audio Console] mounted into the case so Ican adjust the Tacho reading while driving the car. My Tacho is set to the Car's actual speed with my HUD GPS Speedo necessary with my 3.64:1 FORD diff and 185R65 tyres.

Bruce.

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