C43 - how much should engine move on mounts?

[braddo]

When revving a C43, how much should the engine visibly move/rock? Is a certain amount normal or might it indicate a worn engine mount?

My car has developed an exhaust leak around where the manifold joins the rest of the system. When I was looking under the car and pressing the accelerator pedal I was surprised to see the exhaust system moving around.

I don't want to get the exhaust fixed if there is another issue leading to fracturing in the exhaust. On the other hand, the exhaust looks pretty old and crusty so it could just be a case of wearing out.

Thanks!

 

[grober]

V8's produce a lot of torque so a bit of rocking is to be expected--- however a big engine like that will eventually knock its engine mounts out. Quite often the exhaust ends up acting as an engine stay with the results you have experienced. The only way to judge would be to see a C43 with fairly new mounts to compare visually

 

[martyz]

If you can rock it sideways with the engine off quite easily,your mounts need attention.

 

[braddo]

If you can rock it sideways with the engine off quite easily,your mounts need attention.

Do you mean to rock it by hand, or with some sort of lever?

I know the engine should rock to a certain degree under throttle, but is indeed difficult to gauge without another car to compare with!

 

[joecash]

age and mileage would help - as Martyz has said If you can rock it sideways with the engine switched off quite easily,your mounts may well need attention. In good condition the engine should move a small amount but not very much unless you are the "world's strongest man" type. Engine and gearbox mounts do "age" however

 

[braddo]

It's a 1998 C43 and on 99k miles.

 

[BlackC55]

If you can rock it sideways with the engine off quite easily,your mounts need attention.

Quite the opposite actually. if you cant rock the engine side to side the mounts need replacing. They loose their fluid and go hard hence the firmness in rocking it by hand. If they move a lot when running then the mounts are shot too.

 

[balge]

If you watch the engine when it's started up it will give a you good idea of the state of the mounts, if it jumps a long way and rattles around looking like it's nearly hitting stuff the mounts are going or gone.
Didn't bother trying to rock my straight six, bet the V8 is pretty heavy...

This is the idea

mercedes 300d start up - YouTube

 

[kth286]

There should be a spec measurement for the distance between mount body and frame - at least there is in the workshop manual for my 104 engine E class.

I would need to look it up, but 13 mm 'rings a bell'.

So, in my case, if I could not get a bolt head (with 13 mm head - across flats) in the gap; the mount will have sunk too low, and need changing.

Ask one of the techs to find the spec for your car.

 

[braddo]

Sorry for the late reply here but I tried moving the engine by hand today. Pressing on the front corner of the valve cover on each side, the engine would flex a small, consistent amount on each side - let's say a 5-8mm deflection (watching the top of the engine compared to the firewall)?

When starting the engine (from cold) the engine flex was about the same as the 300D youtube video posted above.

I'll see if I can find a 13mm object to check the engine-mount-to-body distance and if it's much different, I'll try to find out from MB tech (a dealer service department?) what the measurement should be.

I get the feeling the mounts are OK. There is certainly no noise from them.

The leaky exhaust is a bit farty but it does add a bit of old-school note to the exhaust so I haven't felt an urgent need to get it looked at.

Thanks for the replies.

 

[Abdul]

Is it possible to get stiffer engine/gearbox mounts for these cars?

 

[grober]

Is it possible to get stiffer engine/gearbox mounts for these cars?

That would defeat the purpose as they are really designed to prevent engine vibration from being transmitted to the body/chassis.Of course if they get worn or sag that's exactly what they will be inclined to do.

 

[guydewdney]

they are easy to change (if you have a lift / pit) and are cheap. Oner of mie was shot (split) so I chaged both. about 50 quid and an hour iirc.

 

[andy27168]

Not sure of the mileage on your car but my mounts lasted about 120-125k miles, I replaced the engine mounts with new ones when I did my 55 conversion, and one thing I noticed when going over speed humps was that the car seemed a LOT smoother especially when coming off of the humps, which I would put down to the mounts being replaced.
Either way if you have no record of the mounts ever being replaced and the fact the 43 is nearly 15 years old my recommendation would be to replace both (always replace in pairs), especially as you have some doubts to their condition, also replace the gearbox mount as well.

 

[kth286]

Is it possible to get stiffer engine/gearbox mounts for these cars?

AS grober, you would not want to do that with a road car.

The Merc engine is in effect 'literally floating on oil'; and that's partly what gives the Merc such good refinement.

 

[Abdul]

AS grober, you would not want to do that with a road car.

The Merc engine is in effect 'literally floating on oil'; and that's partly what gives the Merc such good refinement.

Ah fair play. During my VW days uprated mounts often made a positive difference to the feel of the cars. The obvious trade off is vibration but I didn't find it intolerable.