[Aussiblue]

The NB Fairlane (for those who don't know the NB story for the purpose of this exercise think NA with MPEFI 6 and 4 speed auto and a few NC parts) has developed steering wheel shimmy (vibration in the steering on braking) but only when the car is hot and the there are high ambient temperatures.

For example I just did a long 40 km drive in the relative cool of the evening finished off with several consecutive heavy braking application but there was no shimmy. However, on a hot summer day after the car gets hot (say 10 km) the shimmy appears with all use of the brakes. I have yet to check the front disk runout to see if they are warped but I suspect not as I cannot feels any pulsations through the brake pedal and the discs aren't that old. I have also had warped disks before and it felt different. Nonetheless, when I get a moment I will get out the dial indicator and check.

The suspension seems OK; I can't see any obvious faults, all is tight and it tracks well. I have just replaced the Super Pro poly bushing rack mounts as the rack has kept coming loose and the old bushes had hardened considerably over the new ones. The shimmy was there before I did this and I thought that was the cause. My wife who usually drives the car thinks the shimmy was there all the time until I replaced the mounts (i.e it wasn't temperature dependent).

The steering gear fluid is at the correct level but I think I might try flushing it and adjusting the pad/damper in the rack as well. Anyone come across a similar problem or can suggest the cause?

 

[Aussiblue]

I have found the cause. The universal joint in the intermediate steering column shaft gets loose when hot. I guess that is why they have the heat shield that fits over it and I also guess I am now off to buy a new intermediate shaft. Adjusting the rack pad tightened up the steering considerably and made the source more obvious; when hot the knock can now be induced by simply swinging the steering wheel gently from left to right a few centimetres. Lifting the bonnet while doing this (gently rocking the steering wheels back and forth when the engine was hot) made it easy to hear where the noise was coming from and grabbing and shaking the intermediate shaft confirmed it was loose.

 

[Zoltan]

'Tis good to hear the solution was found. Was it an expensive exercise? I wonder how I would find out whether I need any new bushes/joints etc for the front-end of my NA? To date, (210,000kms) the front tyre wear is always even, and if there ever is a steering wheel wobble, a prompt wheel balance always fixes it.

 

[Aussiblue]

No not expensive just my time.

 

[Aussiblue]

Well I didn't fit the new intermediate shaft as the one I bought didn't fit (the perils of a prototype). Anyway other things occupied me and it stayed as was until recently when I had to fit a new head gasket. After fitting the new head gasket the problem mysteriously vanished. Why; I don't know but I have several hypothesis:

a) moving the power steering reservoir to one side while replacing the head gasket removed a blockage or air bubble or something from the power steering system;
b) the new exhaust gasket is more effective in deflecting heat from that intermediate shaft.
c) the motor has moved on it mounts in some way while pulling the head moving in further away from the steering system.

None very convincing theories and I guess I should just be grateful and forget it.

 

[Aussiblue]

I can't think the just newly leaking head gasket could cause it unless coolant was creating steam in the crankcase that was entering the brake booster via the vacuum hose; but nah that not a known symptom.