How to block and jack up an engine

Question

I have failed engine mounts for my 2010 Mazda 3. I am reviewing the replacement process in the corresponding Haynes' manual which has a step-by-step process for the replacement on 2A-14. In the manual, they say to jack up the engine from the oil pan but place a block of wood under the jack. A few YouTube videos I checked suggested that you can use a block of wood to span the distance of the various components and jack directly to the engine block, especially when just jacking up a specific point to replace a mount.

Is it really the case that one can jack up this engine provided they block the engine off with a piece of wood. On one hand, I understand the pan material is frangible and can deform or crack so perhaps wood will distribute the load. On the other hand, it's not clear exactly how to use wood to jack directly from the engine block. The depth of the pans and filters is certainly greater than 1.5 inches, so do I stack multiple blocks or lay them on the short side? Isn't there a danger that the wood stack will tumble over?

Answer 1

Placing a piece of wood (usually a piece of 2x4" board) between the jack and the oil pan is exactly how I would lift an engine in your case. I use this method whenever I need to change a motor mount or have to remove a motor mount such as doing a timing belt on a 4-cylinder.

The thinking here is the board distributes the force on the oil pan from a very narrow point out to the entire dimensions of the board. This is very much akin to putting the engine on the ground on its oil pan if the engine was out of the car. The oil pan can support the weight without issue, it just can't do it if you put all of the pressure on a very small space. There is no issue with using the board and I suspect it is quite common amongst mechanics, especially considering they are suggesting the method in the repair manual.

As to how to actually use the block, place a single 2x4" length of wood (I'd probably use something at least 12" long, but not so long as it would interfere with other parts of the vehicle). Place it flat side to the oil pan, then put the jack underneath of it about center. Really, this isn't rocket science. The board just needs to be between the jack and the oil pan. Any piece of wood will do, whether a 2x4" or 2x8" or what have you. I wouldn't use plywood as it is not as structurally sound as 2x4/2x6/2x8 pieces of board.

Just for reference, here's a piece of 2x4 which I've used for MANY years doing exactly this kind of work:

As you can see it is beat to heck ... but guess what? It's still structurally sound. I would use it in a heartbeat to do the same job again.