by Pat Goss
A common complaint that we see in my repair shop is my engine vibrates when I’m sitting at a traffic light what can I do?
Well, we start talking to the client and invariably they tell us well I went to another shop and they did a tune up and that didn’t help anything. Well, first the word tune-up should put you on notice that hey, something’s not right because tune-ups really don’t exist anymore. Anyway, that’s a whole different story.
Alright, engine mounts are a common cause of this and how would you go about checking them? Well, you power brake the car, that’s the most basic way to do it, and what means is you hold the brake, put it in drive and accelerate very gently the car doesn’t move, but somebody is out here with the hood open watching the engine to see if it lifts up then you do the same thing in reverse. If the engine lifts up and bumps back down, well you probably have bad engine mounts. Thing of it is, if you have any questions whatsoever about power braking, how to do it or anything, make sure you take it to a professional, don’t try it yourself because it’s dangerous.
Another thing you can do is you can look at the underside of the hood. If you see marks where it’s rubbed clean on the underside of the hood, well you may have bad engine mounts and the engine is lifting up and hitting the underside of the hood. Now another one that we use, which is very effective we take a floor jack and a 2X6, put it under the oil pan of the car, and then at like 1/16th of an inch at a time raise the engine up while this vibration is going on and somebody is sitting in the car. So if the vibration does away, then you do a very thorough inspection of the engine mounts and expect that you will have one or more bad mounts.
Alright, but then the mounts themselves. You see, we have two mounts here, look pretty similar. This one of course you can tell has some age and use on it, looking pretty ragged around the edges, obviously bad. This one on the other hand looks pretty good. Now this is a common problem that we find. This was purchased off of the internet, cheapest guy in town and it is cheap. Now the problem with it is it vibrates as bad as this worn out one because the rubber is not the right compound, it’s hard as a rock. It’s just like bolting the engine to the chassis of the car, and that means that the vibrations, the normal vibrations of the engine are transmitted inside, and that’s what engine mounts are supposed to prevent.
So if you have to buy engine mounts, make sure they’re good quality. Make sure the diagnosis is correct, because some of them have vacuum motors in them, some of them have electric motors in them, some of them are oil filled, there’s all kinds of them and some of them are very expensive so you want to be right the first time.
And if you have a question or a comment drop me a line right here at MotorWeek.