Friday, May 26, 2017

MGB - engine mounts

One of the first things I noticed that needed to be addressed when I bought the little British car was the condition of the engine mounts. "How?" you may ask. I intended to replace the alternator belt and couldn't because the engine was sitting so low in the engine compartment there wasn't enough room between the bottom pulley and the front beam to fit a belt. Today's post covers the fun of replacing the engine mounts without removing the engine from the engine compartment.

virtually 0 clearance
This seems obvious, but there's more to the story than just the rubber mounts. They are sold individually, but they're not expensive. The originals are around 10$US, but there are upgraded versions for 13$US. If you're going through the trouble, it's worth the $6.

The mounts attach to the frame of the MBG onto mount points which are welded on, one per side. These have a vertical slot in the center for the body-side bolt on the rubber mount. The other side of the rubber mount attaches to an engine mount bracket. With the age of these cars, the bracket often has issues hidden behind the rubber mount. My passenger-side bracket was both bent and cracked. Neat. These were $6 a piece. So cheap. Crazy cheap compared to modern cars or even the old bus.

Last, you'll need fasteners. Those old nuts, bolts and washers are as old as the car, and probably more rusty. These old British cars have lots of different metals in them, increasing their tendency to rust. So, get stainless if you can or zinc-coated if you can't. Plain steel will rust again. All of the nuts and bolts fit a 1/2" spanner except the nuts which fit inside those welded-on mount points on the frame and the lower bolt on the bracket. Those are 9/16". To replace the mounts and the brackets, I got 8 1/2" nuts with matching lock washers and 4 bolts, each just 3/4" long. These are all fine thread. I also replaced the bolts on the bottom of the mounting brackets. They need to be 3/4" long. I tried longer bolts but they bottomed out.

bent bracket on right
Similar to most of the other projects I've done on this car, the tool list grows as fasteners get harder to reach or harder to remove. PB Blaster (or a like product from the WD40 folks) is critical. 1/2", 9/16" sockets and wrench. Spanners in the same size plus a breaker bar. Floor jack and a small piece of wood 2x4. With all that hardware, the single most important tool is your patience. I kept running out and having to go looking for more.

Process Out Prep
I read a bunch of different opinions before I started. While the mounts are usually replaced when the engine comes out, it isn't required. Some have found that removing the steering isn't necessary. Not me. I couldn't have imagined this with the steering still in place. See, the steering column runs straight through the welded on frame mount on the driver side, making it all the more difficult to address the nut contained within. Some folks have taken a cheap spanner and ground it down thinner to fit between the column and the mount. Fortunately, I still had my steering unit out, so this was academic for me. My advice: remove the steering rack. See how in (MGB-steering rack).

On the passenger side, the alternator blocks easy access to the mount. This is very easy to remove, and you already have the right tools: 1/2" socket to loosen the belt and then a couple 1/2" spanners to remove the mounts on the top. Don't forget to unplug the 2 wires on the back. And, just like that the alternator is out and you can easily see the mounts.

Once you have clearance to get at the mounts by removing the steering rack and alternator, you're pretty much ready to go. Jack up the front end and put it on stands so you can easily get after it from above and below. Then, put that block of wood on top of your floor jack and set the jack under the rear edge of your oil pan, where it meets the transmission. This is it's strongest point. Raise the jack until the weight of the engine is mostly removed from the mounts, and is instead on the jack/wood combo.

Process Out
Pick a side. To stretch my patience, I would do a little on one side until I grew frustrated and then moved to the other side. Start with the nuts which hold the rubber mount to the bracket. These are the easiest to get to. The bolt closest to the driver doesn't have a bolt head on it so it could free-spin on you. Yes, that's frustrating, but with some pressure applied with a screwdriver between the free-spinner and the engine block, I was able to get the nut off. Next, get after the nut that is semi-captured within the frame-side mount. A spanner can only move about 1" up/down at a time, and then you need to flip it over or use the box-end to move it another inch. This tests patience. Once the nuts are removed, raise the engine until you are able to free the mount from the bracket and frame mount. I also leveraged my breaker bar as a lever to tilt the engine a little bit so I didn't have to raise it as much.
right (p-side) replaced

With the rubber mounts off, remove the bolts holding the brackets to the front of the engine. Last, remove the bolts on the bottom of the brackets. This last bolt is very hard to get to until after the rubber mounts are gone, and even then it is partially obstructed by the sides of the bracket. Patience. Once the bolt is loose, I was able to spin the bracket off by hand, not bothering with anything other than a socket on the bolthead to keep it moving with the bracket.

Process In
The install is the reverse, but it was advice like that which inspired this blog all those eyars years ago, so I'm going to run through it. Start with the bolts for the bracket. Don't torque it down, just get it threaded on and then shift to the smaller bolts which attach the bracket to the front of the engine. The bolts go in from rear to front. While this may not look as clean, the rubber mount will dig into the end of the bolt sticking rearward if you don't do it that way. Yes, I did this first. Once the bracket is loosely attached, torque down the smaller bolts and then the large one. If you do it in the other order, the bolts in the front part of the bracket can get hung up on a slight misalignment and you'll have to do it over. Yes, I did this too. :)

With the brackets in, re-raise the engine so you can fit a rubber mount in. I did the driver side first, but I don't think it matters. The driver-side bracket has that one weird bolt that doesn't have a head. I found something that would work at the hardware store, but needed to bore out the hole in the bracket to get it to sit deep enough so the bracket would align properly on install. Crazy. Once that is solved, plop the driver-side mount onto that bolt and shift it into position such that the frame-side bolt is in the vertical slot. Short sentence; could be a long effort. I used the breaker bar as a lever to help that last little bit of space to slip the frame-side bolt into the slot. Get the lock washers and nuts onto the bolts. I found gravity to be a terrible partner in this, causing the frame-side nut to fall off the bolt and down into the nowhereland of garage floor multiple times. Patience. Once the nuts are threaded on, tighten as far as you can without tools. Remember how hard it was to get the spanner in that frame mount during removal? Yeah, just as hard on install.

left (d-side) replaced
Once you have the nuts threaded on as far as you can by hand, give them a couple of runs with a spanner and then lower the engine so the jack is no longer holding any weight. I tried to shake the engine a little bit on its way down to make sure it settled, but it didn't seem like the engine moved at all. Just the same, its a good idea. Once all the weight is on the mounts, finish the tightening with a spanner.

Finish up by re-installing the alternator, and the steering rack. Lower the car off the stands, clean your hands and your tools.

This job was a bear, but the engine sits at least an inch higher than it was. Between the bent and cracked bracket and the twisted / flattened mounts, this job was long overdue. While the engine won't run any better, I'd like to believe that any vibrations will be greatly reduced and the drive train is now aligned like it should have been coming out of the factory.

As always, thanks for following along. For my American friends, have a pleasant Memorial Day weekend. I greatly miss the old Hornings Hootenanny which used to fill my Memorial Day and am left unsure what to do with my 3 days this year. Maybe I'll pull out the welder...

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