Car Shaking and Vibrating Violently All of a Sudden
Idling extremely rough
Lately, my car has been doing it's own thing, such as squealing and shaking and all sorts of things we all love to hear. The vibrations and shaking just started recently, in a parking lot. When I put the car into reverse it made a loud clunking noise and there on started to vibrate and shake. The shaking was only at idle and in any gear except reverse. This is really enough evidence of a mount failure and needs to be replaced.
Initial thought was the rear mount is bad but because of the difficulty in changing it out I decided with other options which wasn't much. Misfires causes vibrations too, but there wasn't any check engine light, and no hesitation. The shaking and vibrations would go away when revving above 1500 rpm, this kept pointing back at the rear mount, but denial was on full. I decided to crawl under to check and found the mount in two pieces. The fluid within it was all over the undercarriage of the engine and transmission, I was not able to continue to deny the mount any further.
Replacing the rear mount
Replacing the rear mount was a bit easier than I had expected for a 99 v6 Accord, I heard and read about people complaining how difficult it was. Just undo the bolts for the mount to the frame from the top and then the bolts from the mount to the engine from underneath. From up top I had to remove the coolant hose for the heater core and cap both ends to prevent contaminants, this gave enough room to maneuver both piece of the mount out. Do this while keeping a jack under the engine oil pan, best to use a piece of wood to distribute the weight of the engine and prevent damaging the pan.
The worse part is trying to remove the vacuum hose from under the mount, but connecting it back was worse than removing it. The car uses a hydraulic mount so the hose has to be reconnected otherwise you'll experience a vacuum leak, it can be capped off if not in use, but it'll need to be replaced with a solid or non-hydraulic mount.
Rear mount set used
Results from changing the mount
I have three cars and never really used oem mounts as they are very expensive, and to my surprise the aftermarket mounts lasted just as long as the oem. The brand didn't seem to matter if it's installed correctly, the one I had just installed was negatively commented on amazon. Most comments were of negative results right after install. If a mount is installed improperly it will act like a broken mount, there are many reasons for a mount to feel wrong if it's installed incorrectly or broken. The mount is a cushion between the engine and the frame of the car, it holds the engine from bouncing around. If the mount is locked in tightly and properly whether it's hydraulic or not, the car should feel better. Unless you're swapping out a perfectly good mount thinking it was bad, or misjudged a good mount for a bad one.
The transmission should run a bit smoother if it's a mount issue, since a busted mount may put tension between the engine and the transmission. Also, keep in mind that both engine and transmission have mounts which need to be changed whenever they go bad, there are no schedule maintainance as some people may think. Learn to feel your car, listen to it, the noises that a car makes or any machine is telling a story.
The durability of the mounts on the engine and transmission depends on how the driver handles the car. Things like flooring the gas or stopping on a dime is stressful on both the engine and transmissions,
There are some temp fixes to a wrecked mount, people have known to silicone or J-B Weld the mount back together. Some goes as far as to removing the mount to repair, if you can remove it just replace it, any aftermarket mount is better than a broken one. Cheaping out on something which can in turn cause engine or transmission problems is not worth it.
If you need to repair it during a trip, it's fine but most repairs or bandaids are meant to be use for short term. Just as those products marketed to stop leak, majority of them can't stop anything more than a few drops here and there. Some stop leak end up patching up passages that are created for fluid flow, another reason I try to avoid those products.
Temp fixes are meant to be short term, it's meant to deal with the situation until you can get it fixed properly. I have seen people weld together a suspension just to realize it wasn't working after months of preparing and welding. Some things are just too important to leave unattended to.
Self replacement or bring it to a mechanic
Doing any type of work depends on how comfortable you are, but I also believe it's a learning process. I decide to do most things with the car myself, partially because I can see what is being done and it's cost effective. I just enjoy breaking and fixing things. Changing mounts takes a bit of work, and keep in mind that there are torque specs for a reason. I would've recorded the fix but my camera was missing it's battery and I didn't have my charger. Hope this helps in changing the mount.