Subframe replacement
PART TWO: Rob Hawkins returns to Retro Sports Cars to follow Chris Flanagan removing and refitting the rear subframe from an MGF.
After removing the front subframe on the MGF/TF, this month we remove the rear.
In the previous issue of CM, we followed the removal and replacement of a front subframe on an MG TF. This time, we’re looking at a rear subframe on an MGF and showing how Chris Flanagan of Retro Sports Cars removes and refits it.
Overhauling the rear subframe, including having it blasted and powdercoated, doesn’t appear to be as important as it is for the front subframe, which is more prone to corrosion. However, there are a number of jobs that can be completed with the rear subframe removed, such as renewing the subframe mounts, the brake lines that are routed up the engine bulkhead (which are prone to corrosion), the gearchange mechanism for a manual gearbox and the clutch (including the clutch arm that can seize). We’ve also discovered other potential problems can be identified and fixed, such as stress fractures in the bodywork, especially if uprated suspension bushes have been fitted, which can result in cracks around the mounting points for the rear subframe and its suspension dampers.
The work involved in removing the rear subframe is more involved than the front subframe because there’s an engine and gearbox attached to it. While we’ve shown a two-post ramp being used to complete this work, we have heard of owners completing this job using a large trolley jack and tall axle stands. However, this is heavy work, so safety is critical and if you intend to have a go, ensure there are people available to help and you are confident with what’s involved.
The ECU is located 3 on the nearside of the engine bay, and Chris recommended it’s detached and removed along with several other engine loomrelated plugs. The wiring will remain attached to the vehicle when the engine is removed with the rear subframe.
The gearbox oil has
4 to be drained because the driveshafts have to be removed. On the five-speed manual PG1 gearbox and the CVT shown here, there is a drain plug on the base.
The PG1 needs 2.2 litres of MTF94, filled via the filler plug. The CVT takes 4.5 litres of ATF filled via the dipstick.
The exhaust system was removed 5 to avoid fouling the rear bodywork. Using a blowtorch, Chris heated up the three 13mm nuts that secure the silencer to the mid-pipe before attempting to undo them. He also detached the silencer’s straps and unhooked the rubber hangers.
The mid-pipe and flexi-section can be removed to avoid them being damaged when 6 the engine and subframe are removed (they are the lowest point if left attached). Chris removed four 13mm nuts that secure the end of the mid-pipe to the downpipe/manifold.
The coolant needs to be drained and 7 the two coolant hoses were detached from the two steel pipes routed underneath the MGF/TF. Inside the engine bay, close to the bulkhead, another coolant hose was detached. This ensures they are free when removing the subframe.
The front-to-rear Hydragas pipes had 8 already been depressurised, so they were disconnected from underneath by undoing their connections with open-ended 17mm spanners. The rearmost pipes remain attached to the rear subframe.
The live cable between the battery and
9 starter motor needs to be disconnected from the engine side to ensure it’s not dragged out and damaged when removing the rear subframe. We had already detached it when removing the front subframe, but now it was detached from the engine bay.