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DIY: Replacing Engine Mounts

Does your engine bounce around under in the engine compartment? Do you see the cooling fan cutting a hole into the hood? Was that bump you just went over your engine falling out? Maybe you'd better read this before it does.
» Engine Mounts 101
» What?!? Leaking Silicone?
» Electronic-Hydraulic Mounts

What?!?!? Leaking Silicone?
Hydraulic engine mounts are round and have a metal shell. While it is possible for them to leak internally, it is more likely that they will leak externally. Surface cracks are normal and almost always harmless, but if you run your fingers around them and pick up some thick, black goo, you have a leaking hydraulic engine mount. As with any other type of engine mount, replacement is the only option.

In some cases you can get aftermarket solid rubber engine mounts as a replacement to save money. They won't be as smooth as the hydraulic mounts, but they will do the job. If you plan on keeping the vehicle for any length of time, I would recommend putting in the hydraulic engine mount.

Typical Hydraulic Engine Mount

Replacing The Engine Mounts
The engine end and transmission end engine mounts can be replaced separately, if one is bad and the other is good, I would recommend replacing both. Generally if one is bad, the other is not too far behind. If the front or rear engine mount is bad, you need to replace both. If you have a forward facing engine, you need to replace both the left and right engine mounts.

Place a hydraulic floor jack under the engine. If you have to place it under the oil pan, make sure you put a block of wood between the jack and oil pan. Spraying the engine mount nuts and bolts will make removing them easier. Most of the time you just removing the nuts and bolts and raising the engine a bit is all that's needed to remove the old engine mounts. If you have to raise the engine a significant amount, then you may stress and break another engine mount. Check the other mounts and loosen if they look like they will be damaged.

A lot of engine mounts have studs that go through the mounting holes on the frame. Make sure that it is aligned precisely with the hole before you lower the engine. On some engines you will have to work from the top and the bottom of the engine to get all the nuts and bolts started. Sometimes you will need a helper to move the engine around with the pry bar to get a bolt started. If the mounting hole the stud goes through is slotted, let the engine down and tighten the nuts finger tight. Start and run the engine at idle for a couple of minutes to let the engine settle down and then tighten the nuts to specification.

"Dog Bone" And Shock Absorber Type Struts
Some engines use a shock absorber type mount for vertical control. It is usually mounted to the top side of the engine and the bottom bolts to the cross member. Checking this type of engine mount is the same as a suspension shock absorber. Disconnect one end and push it in and out. If it is loose, rough, leaks or has no resistance, it needs to be replaced.

Many engines use a "Dog Bone" strut or two. They are usually mounted at the top of the engine, on the right side, and connects to the radiator support. Sometimes there is one mounted on the front, belt end, of the engine to help out the front engine mount. Sometimes you will find one on the left side, between the engine and firewall, at the bottom center of the engine. If you don't see one on first inspection, look again, it may be buried.

There are rubber bushings in the ends of the dog bone. If they are cracked, broken or distorted, replace the whole dog bone. The bushings can't be replaced separately. When you take a dog bone out, the engine will shift forward so you, or a helper, will need to shift the engine back to get the dog bone in and the bolts started.

Some higher quality dog bone struts have electronic hydraulic controls. These dog bones have hydraulic chambers, almost the same as the struts and shocks for the suspension, so vibration dampening is done hydraulically instead of cushioning by rubber bushings. There is really no difference in feel, it's said that the hydraulic dog bones last a lot longer.

They look a bit complicated, but they are easy to test. Start the engine and turn the A/C on. With the engine idling, disconnect the connector at the solenoid valve. If the engine starts shaking, or the shaking increases, it's working. If it doesn't start to shake, the next thing to do is disconnect the vacuum line at the dog bone to make sure there is vacuum present. If there is, connect a hand vacuum pump to the vacuum nipple on the dog bone and apply vacuum. If it doesn't move, it's no good.

» Part 1       » Part 2       » Part 3
Additional Information provided courtesy of and Warranty Direct
© 2000-2007 Vincent T. Ciulla

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