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MG MGB Technical - Broken/torn engine mount? - 80 LE

I'm fairly certain I posted about this a couple of months ago, so I finally got around to looking at it more closely.

To start off, the engine shakes quite a bit. So much so, in fact, that my OE ZS single carb can hit the hood and has put an outward "ding" on the hood!

I believe someone suggested that the DS mount might be torn, which is logical since that is the side hitting the hood. Upon inspection of the mount, I noticed that one of the two bolts connecting the front (radiator) side of the mount was missing and that it appears be cracked, I thought this was it for sure.

However, once started, I rev'd the motor from the carb linkage to observe and found that mount is not torn at all and is also not pivoting on the single bolt described above. The crack is not separating either.

Could this issue possibly be linked to a mount further down the drive train?

My shifter moves quite a bit when I let off the throttle in the lower gears at a higher (~2500) RPM. Considering the engine/transmission are connected, I don't think this narrows us down very much.

Thanks in advance for your suggestions!
Jeff Grant

The metal bracket between the engine and the round rubber mounts on 77 and later cars do crack, although it takes it's time to work right along the bend. If the gear lever tilts to the right when accelerating then the left-hand engine mount *is* parting. If it tilts forward then it will be the gearbox mounts. I can imagine the carb hitting the bonnet with a broken engine mount, less so with a broken gearbox mount.
Paul Hunt

Thanks Paul. I'll have to check that movement next time I can actually drive it.
Jeff Grant

I checked the movement and the shifter does go from right to left (I believe right when on the throttle, left when off).

I can't see any tears though in the mounts from under the hood.

Considering the horror story I've heard about changing the mount on the rack side, I'd hate to try and change it when it's not an issue.
Jeff Grant

It's sounding like a broken mount, although the lever will always move like this even when the mounts are good, it's just that it moves a lot more when the left side is broken.
Paul Hunt

PS. If the engine is too high on the front mounts then *normal* movement could cause engine parts to hit the bonnet/hood. The studs in the rubber mounts fit in slots, and there are various spacers and locating plates to make sure the engine is in the correct position. This should be with the studs very nearly but not quite at the bottom of the slots. The locating plates should stop them being too high, but if they are fitted round the wrong way, plus too many spacers, it will allow the engine to be installed higher than it should be.
Paul Hunt

Jeff: If you indeed need to replace the engine mount, you may as well do both sides.. From personal experience, if one side fails the other is not too far behind. Yes, the drivers side is not pleasant AT ALL. You can remove it OK, however, getting the nut to thread back on is not an easy task. Some have done it. In most cases you will need to drop the steering rack. The passenger side is more accommodating especially to us driveway mechanics.

Let us know how you fare up.

It would be great if someone would redesign the mounts so one could run the bolt and base of the mount to the car's "frame flange" then attach the mount to the top of the bolt base. Just a re-engineeering idea.

cheers

Gary :>{D
79 mgb
gnhansen

Jeff, the mount could easily be broken but not look like it. I recently changed the mounts on my '76 B and found that on the D/S mount the metal flange that attaches to the engine had separated from the rubber, but it was impossible to tell with the weight of the engine sitting on it.

As far as the carb hitting the bonnet, I'm not sure how much clearance there is underneath, but I can picture a scenario where continuous operation could cause the engine to twist a little more than just revving it with the bonnet open.

Replacing the mounts is a pain, especially with the engine in situ. I've heard that you can jack it up and do it. Of course, with the RB cars, it's best to remove the steering rack to change the D/S mount. I tried buying a very slim bicycle wrench, as recommended by Paul, among others, but it really was too difficult and I felt like I was starting to round off the edges of the nuts. So I pulled the rack. It's not hard, and it was the first time I had done it.

Dan D
Dan DiBiase

Thanks all for your responses. This might turn into a winter project as it's getting chilly here already and one of my climate cables is broken.

Long term effects of broken mounts? Do I need to worry about the engine falling out or flipping in the bay?
Jeff Grant

Jeff: In my case the weight of the engine broke the "good" mount after the passenger side mount had failed. In the end the crankshaft pulley cut a groove in the front crossmember. In short I could no longer drive the car. Also in my case, it was time to pull the engine for a rebuild, etc. So in the end both mounts were replaced as well as the clutch and many other ancillary items.

cheers

Gary :>D
79 mgb
gnhansen

Put a jack under the oil pan. Use a some wood to spread the load. Jack up gently and se if the engine rises. It will tell you if the mount is broken.

Steve
Steve

Good idea Steve. I'll have to try that.
Jeff Grant

This thread was discussed between 10/09/2008 and 23/09/2008

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