As with any work requiring the Car to be raised. Always ensure that it is well supported and cannot move.
NEVER work on a Car that is only supported by a Jack whether a mechanical or hydraulic type.
A Scimitar landing on you will definitely give you a sense of humour failure.
Note: All pictures below are expandable by clicking on image.
Exploded View of Front Suspension at bottom of page.
There is more information at the bottom of the page on things to check while doing this.
No information about a Scimitar would be complete without mention of the Trunnions. ( The suspension is the same as some of the Triumph TR series ). What are Trunnions ?. Basically they are what connects the Bottom Wishbone to the Vertical Link ( Upright ) on the Front Suspension. The bottom of the Vertical Link has a large Thread that screws into the Trunnion. The Trunnion is connected to the Bottom Wishbone by a large bolt, this bolt goes through one side of the Wishbone, through the Trunnion then through the other side of the Wishbone. It is a very simple design but has it's problems. Due to the fact that the Vertical Link screws into the Trunnion continuous lubrication is vital, ignore this at your peril as if there is not enough lubrication there will be excessive and rapid wear due to the weight of the Car at the corner being applied to the thread of the Vertical Link and the thread of the Trunnion. Not only will there be wear but the threads will become tight resulting in stiff steering ( There are other reasons for stiff steering ). If this is ignored the Bottom Wishbone will become detached from the Vertical Link due the excessive wear of the threads. When this happens the Road Wheel and Vertical Link goes upwards into the wheel arch and the Bottom Wishbone goes downwards into the road surface. You will be left with very little steering ( If any ) and hope your luck holds with any brake pipes not being damaged, you would not want this to happen at any time especially at speed and in traffic, imagine this happening at motorway speeds !. Nowadays this design would not be allowed on a Car as there is not a safety margin. Look at the Top Ball Joint attached to the Top of the Vertical Link, If excessive wear occurs here the worst that can happen is it becomes loose but will not become detached. To check wear in the Trunnions is not difficult but if they have been ignored for a long time they could give the impression that they are OK. Lifting the Car and applying leverage to the Trunnion will not always show any wear, you will need to get the weight of the Car off the ground but with the Road Wheel still resting on the road. What you are trying to do is prevent the weight of the Road Wheel applying sideways pressure to the Vertical Link and so "Taking Up" and wear. My advise is unless you are 100% sure that you know the history of the Car replace the Trunnions. Now what a nice easy comment that is, this is one area that you could have some real fun especially if there has been nothing done here for a while. The main problem is the bolt that goes through the Bottom Wishbone and Trunnion will likely be VERY tight. This is due to where the bolt goes through the Wishbones there is a steel insert in each side of the Wishbone. This results in the bolt becoming rusted to each insert, it is quite likely that this bolt will not become free from the inserts. Before starting have something to put things on ( Newspaper ) as it is not a good idea to put things like bearings etc direct onto the ground. To get at this area you will need to remove Road Wheel, Remove the Brake Pads by removing the small "R" clips that go through the pins that go through the Brake Pads, slide out the Pins then slide out the Brake Pads. If it has been sometime since the Brake pads have been removed they may need a good "wiggle" as they could well need to get passed the edge of the Brake Disc. Try pushing the Pads towards the Brake Caliper, this will push the Caliper Pistons inwards allowing more room to slide out the Brake Pads. NOTE: if you are pushing the Caliper Pistons inwards remove the cap from the Brake Master Cylinder and have a large rag ready below the Master Cylinder as when you push the Caliper Pistons in you will push brake fluid back to the Master Cylinder and it could overflow spilling fluid out of the Master Cylinder. You do not want to get Brake Fluid onto any paintwork as Brake Fluid is an excellent paint stripper. Now undo the nut that holds the backplate and two bolts that hold the Brake Caliper to the Vertical Link, ( There will be a plate behind the two bolts that will be bent over the flats of the bolts, these will need to be moved away from the bolts, they are there to prevent the bolts from becoming loose ).
Once these nuts/bolts have been removed there will be nothing holding the Brake Caliper so take care as there is a Brake pipe attached. You will need to move the backplate away from the Vertical Link, it will need a bit of a "wiggle" but try to get the lower part sorted first. Once the backplate is free you will now be able to move it complete with Brake Caliper and tie it out of the way. NOTE: the Brake Caliper will be attached to the backplate by the brake pipe and the whole assembly is attached to the Car by the flexible brake pipe so do not but any strain on this assembly. Once the Brake Caliper and backplate are out of the way remove the Brake Disc. This is done by removing the center cap and split pin then removing the nut.
Take care when you remove the nut as the Disc may try to fall off. Behind the Nut is a tapered bearing, Holding the bearing in place with the Disc pull it off the Stub Axle. Place this assembly on the Newspaper as you do not want any dirt or grit getting into the bearings. Now remove the Steering End Stop, you will not be able to unscrew the Trunnion from the Vertical Link with this End Stop in place.
Now the fun starts, removing the bolt that holds the Trunnion to the Bottom Wishbone. The first thing to try is to hope that penetrating oil will work. Use Plus-Gas as that is the best, WD40 is not a penetrating oil despite what is says on the tin. Give the area a good soaking in Plus-Gas every day for a week in the hope that it will soak in by the weekend. Take care not to get anything on the Brake Disc. The application of heat will not work here due to the inserts being in the rubber mounts. If you did release the inserts from the rubbers they would still be attached to the bolt and the inserts are bigger than the holes in the trunnions. Don't be fooled in thinking all is loose because the bolt turns, the inserts could well be still rusted to the bolt and twisting in the rubbers, the inserts are bigger that the hole in the Trunnion so will not slide out. There will be the temptation to use a big hammer, give it a try but if they are not going to shift after a couple of thumps you will be wasting your time as most of the impact of the hammer will be taken up by the rubber mounts flexing. There are now many options to try, Here is a few suggestions. Unbolt the Bottom Wishbone from the Chassis, unbolt the Shock Absorber / Spring plate from the Bottom Wishbone, you will now be able to separate the Bottom Wishbone and one side will come off the bolt. This assumes that you have removed the nut. If this nut will not come off there is no option but to cut it off, Hacksaw or Angle Grinder. ( Note: if you are going to replace the Trunnions order two new bolts. These bolts normally come as a kit with all the washers, spacers etc ). Assuming that you have removed the nut and parted the Bottom wishbone you should now be able to attack the insert that is rusted onto the bolt then slide off the Trunnion and get the bolt out through the other side of the Wishbone. Another option is to slide a hacksaw blade between the Trunnion and Wishbone and cut through the bolt, make yourself comfy if you are going to do it this way as the bolt will take a lot of effort to cut through. There are many ways to remove the bolt, I will leave you to your own ideas, once the bolt has been removed you will now be able to unscrew the trunnion,
As all the good books say reassembly is the reverse of the above and this is true. You may want to replace the rubber mounts when doing this and some suggest fitting grease nipples to the Bottom Wishbone to ensure that grease can be injected into this area. I have fitted stainless steel inserts so the bolt will not rust to the stainless inserts. Make sure that you replace the seals that are fitted between the top of the Trunnion and the Vertical Link. This will ensure that water etc does not get into the Trunnion to Vertical Link threads. When assembling make sure that there is plenty of grease in the Trunnion and inserts. Screw Trunnion onto Vertical Link, Trunnions are Left and Right Handed. You will not be able to fit the wrong Trunnion to the wrong Vertical Link as the threads are different. The Trunnions should be marked with a L or R for left or right. When fitting the Trunnions screw then up as far as possible then back to align with the wishbone. Take care that you have not put to much grease into the Trunnion as it may not screw in as far as required. Once fitted with the bolt in place you can now inject as much grease as possible until it starts to ooze out of the Trunnion to Vertical Link seal. There is a grove in the Trunnion to allow grease to get at the threads,
There are many opinions what type of grease to use. Some say use a light grease mixed with oil, some say mixing with oil not required. This is one of those question you could ask 10 different Scimitar owners and get 11 different answers. I use a normal Moly grease and apply it with a grease gun every 1000 miles, it's not difficult to do and only takes 10 minutes.
There is a potential problem with Trunnions as supplied nowadays. The bottom of the Trunnion has a plate that is held in place by the main body of the Trunnion being pressed over it so holding it in place. When grease is injected into the Trunnion it can force this end plate away from the main body.
Sorry for poor picture.
I am unsure if this happened to Trunnions years ago but it is not a good idea to have the bottom of the Trunnion open as water etc will get in. Before fitting the Trunnion it is a good idea to solder over the end so ensuring the end plate stays in place. In the words of Monty Python I hope I am not "stating the bleeding obvious" but a blow torch will be required to do this soldering, a Soldering Iron will not be able to supply enough heat to do this.
Reassembly is a reverse of the above. Once the Trunnions, bolts etc fitted it's now time to fit the discs. Give the Disc Hub Bearings a good grease. One idea is to remove the bearings and give them a good clean and apply new grease. When fitting the Disc do not tighten the hub nut yet, just enough to hold the Disc in place. Now fit the Brake Caliper and backplate. Remember to take care as it is still attached to the Brake Pipe. Loosely fit the bolts and the nut ensuring that the locking plate for the Caliper bolts is fitted and the correct way round. It has a cutout along one edge, this cutout should be towards the Caliper or you will not get both bolts to fit. Now fit the Brake Pads, retaining pins and "R" clips. The reason for not tightening the Disc hub nut or Caliper Bolts is to allow you to "wiggle" both the Brake Disc and Caliper so helping the Brake Pads to be fitted. Once the Brake Pads are fitted tighten the Caliper Bolts and Disc Hub nut, not too tight with the Disc hub nut yet. Remember to bend the Caliper Locking Plate around the bolts. Give the Disc a few turns then press the brake pedal a few times to align the pads etc. Check the fluid level in the Brake Master Cylinder. With the Center Hub nut cover still removed fit the Road Wheel, once fitted you need to tighten the Hub Nut. This needs to be tightened to remove play from the Hub Taper bearings but not so much as to be to tight. Spin the Wheel as you are tightening the nut, there will be a point where tightness/drag will be apparent, once this point is reached turn the nut back until it frees but check by holding the top and bottom of the road wheel and pushing and pulling the Wheel check for play in the bearings, it will be obvious. What you are trying to achieve is no play but no tightness, there will be a point between the two just take your time until you get the feel of it.
Once you are happy it is now time to fit a split pin through the Hub Nut and then refit the center cap and tighten and torque the Road Wheel nuts. Go for a drive and when safe to do so check the Brakes, give them a good shove to make sure all OK. Best to check when safe than find out there is a problem later.
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The above is my explanation on how to replace the Trunnions. As you are doing this it is a good idea to check other things. When all disassembled check the tightness of the nut that holds the Stub Axle to the Vertical Link. If this is loose apart from the obvious dangers it will give you the impression that the Wheel Bearings are loose when you try to adjust with the Hub Nut. Also when all disassembled check the bolts that hold the Steering Arm to the Vertical Link. Other things to check is the condition of the Steering Rack Gaiters and the Top Ball joint. The question of what type of fluid to use in the Brake Master Cylinder is a common subject. There are many who say that they use silicon fluid without any problem. One of the problems with using normal fluid is the fluid absorbs moisture and so can corrode the bores of the Master Cylinder, Rear wheel Cylinders and Front Calipers. This is not a problem if the fluid is replaced every year, using silicon Brake fluid eliminates this problem as it does not absorb moisture. The problem with silicon fluid is it can swell the rubbers in the Master Cylinder, Rear Wheel Cylinders and Calipers. I have contacted the manufacturers who categorically advise against the use of silicon fluid in this type of system. There will be some who say they use silicon without any problems and there are others who advise against it, my thoughts are I do not use silicon fluid as I do not like any doubts when it comes to the brakes. I have given this information for you to make you own decision. I am going to take the advise of the manufacturers who in my opinion know best. To me it's not a big job to replace the fluid every year.
I hope the above has helped as the Trunnions are a very safety critical area that should not be ignored.
Good Luck. Don Kennedy