mini love - part 21

The Mini has not been running well the last week. It all started when it hit a big pothole when we went grocery shopping at the other side of town.

While trying to get around some distracted driver I took a lane change that is legally permitted. I had to complete the maneuver quite quickly. I knew that lane has very rough pavement but I didn't expect a new pothole. The speed was around 40 mph when the Mini left front and then left rear wheels hit the pothole. It was the worst of any that I had ever experienced. The suspension bottomed out and the struts hit the bump stops. Immediately my heart sunk because those are very expensive wheels that are no longer available. If I could I would buy one extra as spare for accident like this. I was quite sure one or both wheels are bent from such violet pot hole encounter at speed. When we got onto the highway I could sense something does not ride right with the Mini. There were subtle vibration that I was sure not there that morning on the outbound trip.

Arrived home I immediately inspected the wheels. There was no visible damage to the wheel to the naked eyes. Next I put the Mini up on jack stands for more thorough check. I hand spun the wheels and again saw no excessive runout of the wheels.

Next is to examine the wheels more closely, with a machinist's dial gauge. All wheels, however perfect, have certain amount of runouts, laterally as well as longitudinally. Since I have no know figures I have to rely on my own intuitions.

checking the rim runouts with a machinist's dial gauge

I compare the deviations of the front to that of the rear and they are quite comparable. Since the front took the blunt of the impact I would expect it to be worst. It was a very hot day and I thought the wheels are probably fine.

The weather was extremely hot and sunny for the next few days. I drove the Mini a few times and it was quite clear it rode badly. The dash and glovebox rattles worst than ever. There is this vibration on the steering wheel that I was sure not there before. The vibration is not the shimmy kind caused by the wheels. It felt as if the alignment is off kind of vibration. I am quite in tune with how well should all my vehicles drive and I can definitely tell something is badly wrong. May be the alignment on the left side was badly compromised from hitting the pot hole. I could not sleep well a couple of nights thinking some thing bad had happen to the Mini, and it may never ride right as before hitting the pot hole.

A few days later the weather cooled. This time I want to to get to the bottom of the problem. Again I checked the wheels with the dial gauge, but this time I checked also the right side wheels. All the runout figures are very comparable - so the wheels are fine.

Next I check the runouts at the tire threads. I use a block of wood to provide a stationery reference. I have been doing this since high school days and I have a pretty good idea how much runouts would begin to cause a noticeable ride impact. All tires have runouts laterally as well as longitudinally, and they are larger than those of the rims. All these tires are very new and have only 1/2 of a track day use on them.

check across the width of the thread while spinning the wheel by hand

I also check the laterally runout

another view so you can see how I do this

All four wheels are quite good, and are within my experience that would begin to adversely affect the ride quality as well as steering shimmy.

Next is to check for front strut damage, including the strut tower. The left tower does not look any different from the right side.

left (driver) side tower

right (passenger) side tower

Next I remove the left front strut assembly to check for damage to the strut or the top camber plate.

The 3/8" thick camber plate has a very slight bent. It is so slight that can be detected only with a straightedge. I carefully restored the flatness with a ballpeen hammer. Obvious so far nothing I found can be linked to the deteriorated ride and increased in vibration and interior rattles. What could it be? I took the Mini off the jack stand and went for more test drives. My test drives confirm that it ride badly and the rattles is not my imagination or loose items in the glovebox. I know the Mini never have dash rattles this bad. I was also very sure that the steering wheel vibration is new, as the Mini was silky smooth and vibration free after the recent performance upgrades. It was so smooth that I knew it rode better than when it was brand new back in 2004.

That afternoon, I went out and look at the Mini with a glass of wine in hand. As it was the first time too I felt a slight hesitation when accelerate somewhat hard. Coincidentally that occur on a first day of high humidity (about 85% RH). I popped the bonnet to just look at the ignition cables. They are original so are now 13 years old. I have always been very careful with ignition cables when replacing spark plugs to not cause any stress on the wire jackets and the rubber boots. I looked for signs of high tension leak around the jackets and the rubber boots. There are some accumulation of dust particles near the boots by the coil pack. I deem they are normal from the high tension voltage as no insulation is perfect. Still I think it is time that I should order a set of cables by NGK. They are quite inexpensive.

As I proceed to do a visual run over of the engine compartment I spotted something. The bolt that withstrain the right side engine mount from fore/aft movement is loose! The bolt has worked itself out by about 5 mm. I figure when I recently replace it with a new OEM mount, I must have neglected to torque it properly as my mind was preoccupied with the other bolts that requires much higher torque. I am very glad of happen to spot this oversight of mine and caught it before the bolt falls out completely.

 I torqued up the bolt using my guestimate based on it is a 16mm bolt.

Actually before I caught this loose bolt, I have inspected the lower engine mount (MINI maunal call it engine mount damper).  On one side the rubber gourmet has some slight tear but I know they are good for awhile. I have one order and is on the way.

the engine mount damper has slight tear/crack on the gourmet on this side

the other side has no tear

So how much ride impact did this loose bolt on the engine mount has? Only a test drive can tell.

Wow! All the bad ride quality is gone. Totally disappeared too are interior vibrations and rattles. No more steering wheel vibration or shimmy. The Mini rides as silky smooth as immediately after the performance upgrade. That evening when the traffic lighten up, I took the Mini out for a spirited drive, with hard cornering, wide open throttle accelerations, and hard braking with heel and toe downshifts. The difference is astounding, all because of a loosen secondary bolt on the right side engine mount. The Mini and I are both very thrilled.

I know very well that my choice to stay with the factory OEM hydraulic engine mount is a sound decision. I know that my decision to stay with the factory OEM engine mount damper is also a sound judgement, as with my decision with the Irish Engineering fixed camber plates which has rubber damping.

a smooth riding Mini is a happy Mini

Update - 2017.09.11:
Today I was just browsing some photos. I realize the line and notch on the rubber bushing of the lower engine mount damper look like tears, but are in fact how they look even new.


here is a photo for a new one being sold

here is my photo which I thought there is a crack line and a small tear on the edge

Now I am going to have a spare one when it arrives and I paid only half price for one.