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W110/W111/W108/W109/113 front subframe mounts

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This advise is related to all W110, W111, W112, W108, W109 &W113 chassis cars. 

Lifting a W110, W111, W108 or W109 chassis vehicle on a 2 post hoist can lead to failure of the front suspension cross member mounts. When you lift the car with the front wheels hanging in space the entire weight of the engine/transmission and front suspension is supported by the front subframe mounts (sometimes called tower mounts), the front shocks and the flat spring at the front of the cross member. The pressure this puts on the subframe mounts can tear the rubber away from the steel with the result being that almost all the weight winds up being put on the shocks and flat spring..

The other potential disaster for cars with a fan shroud is that if you start the engine with it on a two post hoist the fan can fowl on the shroud as the engine will drop anything up to 3-4cms. 

To gain a better understanding of how this a problem, try lifting your car on a 2 post hoist just a little bit (without the front wheels leaving the ground) and look at how much the mounts stretch. 

The pictures below show good (or new) mounts in green and bad ones in red. They then go onto show how we solve the problem in our workshop. The solution is rather simple. 

1) With the vehicle sitting on the ground, weight supported on the front subframe, remove the bolts that attach the subframe mount to the subframe. These are accessed on the  l/h side of a RHD vehicle by removing the battery. 

2) Place a 100mm x 80mm x 8mm steel plate with a 13mm hole drilled in the centre over the four bolt heads for the bolts that hold the subframe mount to the body.

3) Place a 130mm M12 high tensile bolt though the plate and screw it into the subframe. Tighten the bolt until the mount is just being compressed, you will have to look under the guard to see this. 

4) Lift the car on a two post hoist. The weight of the front subframe and engine is now suspended on the bolts. The vehicle can be driven on a limited basis with these mounts in place, but obviously common sense should be observed.

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Broken mount - new mount
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Green good, red broken
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Broken mount
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Subframe mount about to tear
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Subframe lock
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M12 bolt
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Lock installed
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W109 300SEL 6.3 on a two post hoist.