SUB-FRAME Replacement of the rear sub-frame is occasioned more often by corrosion damage than accident damage, as this appears to be the Achilles Heel on these models. Repair, in terms of 'plating' the affected areas, should only be regarded as a temporary measure as replacement of the sub-frame is the only real answer.
Removal 1. Disconnect the battery leads and remove the battery. The non-earth lead (positive or negative, dependent on the age of the car) to the front of the car will have to be released from the luggage compartment to allow it to clear the sub-frame when it is removed. This is best accomplished either by cutting the terminal off the end of the battery lead and fitting a new screw-clamp type one on reassembly, or by making the hole in the luggage compartment floor big enough to allow the existing terminal to be pushed through. If the floor panel is pulled back carefully to minimise the amount of tearing, it can be easily pushed back on reassembly and the tear sealed with a suitable body sealer.
2. On Hydrolastic models, the Hydrolastic suspension system on both sides of the car should be depressurised before the car is jacked up. However, remember that the ride height of the car will drop as the system pressure is released and it may then be difficult to get a jack underneath the rear.
3. Jack up the rear of the car to a suitable working height, bearing in mind that sufficient clearance should be left to lower the sub-frame. Support the rear end of the car securely on stands at the jacking points at the rear ends of the sill panels. Remove both road wheels.
4. Detach the complete exhaust system and remove it from under the car.
5. At each rear brake assembly, remove the clevis pin and disconnect the handbrake cable from the lever at the backplate. Also detach the cable from the abutment bracket at the backplate. At the handbrake cable sector on the underside of the radius arm, lever back the flange at the sector corners where it retains the cable and release the cable from the sector. Pull the cable through the subframe towards the centre of the car and detach it from the guide plate at the centre of the sub-frame.
6. Disconnect the main brake pipe from the brake pressure regulating valve on the sub-frame. Fit a suitable plug in the valve and cap the pipe end to prevent loss of fluid and the ingress of dirt (and stop brake fluid dripping onto you!).
7. Support each radius arm in turn and remove the shock absorber ('dry' suspension) or disconnect the helper spring from the radius arm (Hydrolastic suspension). On 'dry' suspension models, leave the fuel tank in its removed position as access to the sub-frame rear nearside mounting bolts will be required later on.
8. On models with the fuel pump mounted on the rear sub-frame, disconnect the fuel pipes and detach the pump, together with its mounting bracket from the sub-frame. Plug the fuel pipe from the tank to prevent loss of fuel.
9. On Hydrolastic models, disconnect the Hydrolastic pipes from the valve assemblies at the sub-frame rear crossmember. Take great care when releasing the pipe unions as these pipes are easily crushed if excessive force is used. If the pipes are corroded, the unions may break off and new pipes will have to be fitted on reassembly.
10. Support the sub-frame on wooden blocks, or something similar, at the brake drums and the sub-frame front crossmember. A wooden plank about 36 inches long, bearing on the sub-frame sidemembers will also do.
11. Where fitted, remove the end finishers from the rear ends of the sill panels. The finisher is merely a piece of trim and is secured in position by screws - these will probably shear off when unscrewed. On reassembly the finishers can be left off as on the later models.
12. The four sub-frame mounting blocks can now be unbolted from the body. The mountings are located at each comer of the sub-frame and a fair bit of poking with a screwdriver may be required to uncover the securing bolts from the accumulated road dirt.
The two bolts at the front mountings go forward into tapped holes in the crosspanel on the body, whereas the rear mountings are secured by bolts and nuts through the floor panel on saloon models, or merely bolts into tapped holes on Estate, Van and Pick-up models and . On saloon models the rear mounting bolts are accessible from inside the luggage compartment, but the fuel tank will have to be displaced to gain access to the near-side bolts. These rear mounting bolts can be sheared off if seized, or at worst drilled out from inside the boot, but if the front ones shear they must be drilled out and the hole retapped to size.
13. Carefully lower the sub-frame assembly out of position, or lift the rear of the car up to clear the sub-frame. It may be necessary to lever the mountings clear of their body locations to release the sub-frame.
Installation Installation is mainly a reversal of the removal procedure, noting the various points mentioned during removal.
If the either of the Hydrolastic pipes is corroded or was damaged during sub-frame removal, it should be replaced as detailed later in this section, before the subframe is installed.
When installation is completed, bleed the braking system as detailed in the BRAKES section.
On Hydrolastic models, evacuate and repressurise the Hydrolastic suspension system as detailed later in this section.
Replacement If a new sub-frame is being fitted, all the components should be transferred from the old unit. This should be done systematically, and it is recommended that the sequence of removing the parts from the existing subframe be noted down to facilitate their reassembly to the new unit. A few points of note when building up the new sub-frame assembly are given below:
a) Renew any brake pipes or hoses which appear in any way defective. When fitting a new brake pipe, use the old pipe as a template for bending the new pipe.
b) Mark the locations of all clips, brackets, etc., on the new sub-frame with paint, using the old sub-frame for reference.
c) Check that the hole for the radius arm pivot shaft in the new sub-frame has sufficient clearance for the shaft to fit in easily. It may be necessary to relieve the hole with a round file.
d) Check that the threads in the bolt holes for the pivot shaft support bracket are clear and not clogged with paint by screwing in the bolts prior to assembling them properly.
e) Change over the parts of one radius arm assembly first so that the position and location of the components can be compared.
f) If the radius arm pivot shaft bearings are worn, they should be renewed before assembling the radius arm assembly to the new sub-frame.
g) On models with Hydrolastic suspension, do not forget to change over the radius arm bump stops from the subframe front crossmember. Each is secured by a nut and bolt.
h) On models with Hydrolastic suspension, it may be necessary to saw up old sub-frame in order to release the Hydrolastic valve connector assemblies from the subframe rear crossmember, if the retaining nuts are seized. It should then be possible to slacken off nuts with the assemblies secure in a vice. A spark plug socket spanner fits these nuts.
i) When changing over the Hydrolastic displacer unit, ensure that the plastic sleeves at the hose apertures are also changed over. These are secured by three cross-head screws.