A Mounting Problem - Diagnosing & Replacing 240 Engine Mounts
Broken, oil soaked or worn motor mounts are a common problem we see. It's amazing how often people will have a bad motor mount and not even notice it. This might be attributed to the fact that this is because a bad mount creeps up on you over time almost imperceptibly. We have seen more than one engine ruined for want of a motor mount. If the passenger side mount should let go, the oil filter can be punctured and dump out the crankcase oil in short order. The driver side mount often fails early in it's life leaving the passenger side mount to perform double duty, a role it is incapable of performing for very long. On most Volvos the passenger side mounts are exposed to high heat from the exhaust manifold, oil contamination from leaky cam cover gaskets and repeated oil soakings when the oil filter is changed.
Volvo motor mounts are made to break away in the event of severe frontal impact and allow the engine to be pushed back and underneath the car for safety. Their job is to hold the engine in place and to provide important vibration damping. If you have never changed the motor mounts, inspect them soon. Look for excessive bulging caused by oil contamination, which softens the mount to the point that it can no longer control engine movement. Also look for signs of broken mounts where the vulcanized metal plates have broken away from the rubber portion of the mount.
While you’re at it, inspect the transmission mount for the same failures. Broken motor mounts increase the loads on the transmission mount. When transmission mounts fail they can make shifting gears difficult if not impossible. They can also get soft and sag until the shifter drops down. This is more apparent with a manual transmission than an automatic. There are two styles of transmission mounts found in the 200 series, round and square. The round style can be upgraded by using the B30 engine mount which has the same configuration but is heavier duty than the OEM transmission mount.
One of the symptoms of worn or broken motor mounts is that the engine moves around a lot, causing the shifter to rock back and forth at idle or when shifting. In any case, the engine will rock excessively under throttle, which will speed the decline of any failing motor mount. On any Volvo you may be able to see engine mount problems from above if you brace yourself against a solid part of the engine and rock it from side to side (engine off!). Movement of more than 1/4” usually means there’s a problem. You can also see excess movement when the engine is running if you open the throttle.
You can best see a broken mount from underneath. Note that sometimes a mount can look perfectly good, but in actuality it is broken in half, so it’s smart to jack the motor up a bit to confirm that the mount is still in one piece. On my cars, I try to remember to look them over at oil change time. Sheared mounts can be hard to detect on an engine that is stationary, but soggy oil soaked ones that have allowed the metal plate to dig into the rubber are easier to identify. I have seen at least one occasion where movement of the engine would cause wires to loosen at the coil and cause the engine to die when shifted into reverse; Talk about a puzzler!
I have also heard harrowing tales of high performance engines breaking free of their mounts under heavy load and causing massive damage. Once you have found a bad mount, it is wise to replace it as soon as possible. This is a relatively easy job for a do-it-yourselfer to accomplish, but it must be undertaken with care, as the weight of the engine must be lifted off the mounts. You can use a hoist to lift and support the engine or use a jack and a block of wood under the oil pan. In either case, we recommend using a block of wood between the oil pan and the cross member for extra support (don't forget to remove this block before letting the engine down!). A set of drive on ramps will work well for this job, otherwise, jack the car up and support it well on jack stands. Be sure you choose a firm, preferably paved surface for this, as I have seen jack stands cut into fairly solid ground and allow a vehicle to tip over. Any good manual will guide you through the steps necessary to renew your motor mounts.
When replacing 240 mounts, here are a few tips from my experience:
1.My Haynes 240 manual suggests that the power steering hose will have to be unbolted and set aside, but I have not found this to be essential.
2.Be sure to disconnect the battery, as it is all too easy to bump into the alternator or starter hot lead with shocking results.
3.In general it is much quicker to leave the bracket bolted to the engine and use a thin walled 17mm socket to remove the nut that holds the mount to the bracket.
4.If you do remove the brackets from the engine block, be sure not to over torque the bolts when you replace them. Over tightened bolts could shear and allow the engine to fall over onto the oil filter with disastrous consequences.
5.As with any project, be sure to get all threaded fasteners started before tightening any of them down all the way. This will allow everything to go back into place more easily.
If you plan to change the transmission mount, do so after the motor mounts are back in place so that the engine and tranny have some support when you drop the transmission crossmember. Support the gearbox well and remove the crossmember to install the mount.
Naturally, in the words of Haynes "Refitting is the reverse of removal."