[roastbeef]

I just took a look under the hood of my fiance's 335d. I wasn't really looking for anything, just some routine visual inspecting. Found what look like surface cracks on the driver's side engine mounts. Is this maybe just the surface corrosion, or is this a common part that fails?
I know on my m3, the motor mounts take a dump pretty quick with track use. This is a city car though, completely stock power.
Check out this potato cam pic.

[Yozh]

First time someone would have cracks like that. May wish to have a better close up picture. Could it be liquid marks from a spill?

[roastbeef]

Originally Posted by Yozh

First time someone would have cracks like that. May wish to have a better close up picture. Could it be liquid marks from a spill?

Not liquid. I didn't pick at it or anything, but they are definitely cracks.

[Yozh]

Very strange. But should easy to replace. Test the vacuum on that drivers mount and replace at the same time while you are at it.

[roastbeef]

Originally Posted by Yozh

Very strange. But should easy to replace. Test the vacuum on that drivers mount and replace at the same time while you are at it.

Vacuum? Like make sure it's not leaking that liquid?

[Hoooper]

Mine looked just like that, looked like casting imperfections. They were raised up ridges rather than depressions like cracks would be

[335stoner]

I would say casting imperfections also...

from the pic it looks like they are in the shape of circles which could be from where they poured the cast...(????pure guess????)

I would not worry about it by the looks.. if it were a line going from one side to the other I might consider replacement. I would say keep an eye on it maybe hit it with some brake clean and call it a day...

[BB_cuda]

Mark edges of imperfections with a sharpy. Look back later to verify "what if cracks" don't propagate past the marks. Just a quantitative way to gauge. I'll look at mine too.

[roastbeef]

Also, what's the deal with the open intake tube that sucks in hot air behind the turbo? Does it help flush the intake with cooler air (like an outflow)?

[BB_cuda]

I see same features in my driver's mount bracket. Road grime makes the casting lines look more like cracks. I wiped it down and doesn't looked cracked anymore. One of the lines was more inward as opposed to a protruding ridge. Just my two cents but something like that should be buffed down. Things like this are sites where cracks can better initiate from. I'm not a fracture guy though. Casting is very beefy so we shouldn't worry. Thanks OP for pointing this out. I will look heee when I check oil level.

[chenry]

Originally Posted by BB_cuda

I see same features in my driver's mount bracket. Road grime makes the casting lines look more like cracks. I wiped it down and doesn't looked cracked anymore. One of the lines was more inward as opposed to a protruding ridge. Just my two cents but something like that should be buffed down. Things like this are sites where cracks can better initiate from. I'm not a fracture guy though. Casting is very beefy so we shouldn't worry. Thanks OP for pointing this out. I will look heee when I check oil level.

My passenger one went out around 70k

[Hoooper]

Originally Posted by roastbeef

Also, what's the deal with the open intake tube that sucks in hot air behind the turbo? Does it help flush the intake with cooler air (like an outflow)?

That tube has, or should have, a spring closed valve on it. The theory is that if the filter or intake gets clogged it pulls the valve open and the maf detects the error based on the hotter air temp. It should be normally closed.

Originally Posted by chenry

My passenger one went out around 70k

The metal broke or the mount wore out?

[roastbeef]

Originally Posted by Hoooper

That tube has, or should have, a spring closed valve on it. The theory is that if the filter or intake gets clogged it pulls the valve open and the maf detects the error based on the hotter air temp. It should be normally closed.

is the valve inside of the tube? mine doesn't appear to have anything on it. is the valve inside of the tube or attached to the airbox?

[chenry]

Originally Posted by Hoooper

That tube has, or should have, a spring closed valve on it. The theory is that if the filter or intake gets clogged it pulls the valve open and the maf detects the error based on the hotter air temp. It should be normally closed.

The metal broke or the mount wore out?

Sorry couldn't tell you specifically I had some obvious indications (now that I look back)...took it to the dealer and it was fixed under my extended warranty

[Hoooper]

Originally Posted by roastbeef

is the valve inside of the tube? mine doesn't appear to have anything on it. is the valve inside of the tube or attached to the airbox?

It's on/in the box. If you pop the lid off you should see it

[335stoner]

Originally Posted by Hoooper

That tube has, or should have, a spring closed valve on it. The theory is that if the filter or intake gets clogged it pulls the valve open and the maf detects the error based on the hotter air temp. It should be normally closed.

I haven't had the air filter out of my car to peek at that valve, but it sounds like y'all are taking about the pre air warmer thing... I don't know what it is exactly called, it should be before the air filter itself not after. at least that is how I have seen it on my other cars???

I thought that that was a warm air path for when the car is cold that spring holds the flap open to allow the warmer exhaust air into the intake to help the motor warm up faster. then as the car reaches operating temps the hotter exhaust air lets the flap close and then it uses the air from the intake..??

[Hoooper]

Originally Posted by 335stoner

I haven't had the air filter out of my car to peek at that valve, but it sounds like y'all are taking about the pre air warmer thing... I don't know what it is exactly called, it should be before the air filter itself not after. at least that is how I have seen it on my other cars???

Yes, its on the pre-filter side of the intake.

Originally Posted by 335stoner

I thought that that was a warm air path for when the car is cold that spring holds the flap open to allow the warmer exhaust air into the intake to help the motor warm up faster. then as the car reaches operating temps the hotter exhaust air lets the flap close and then it uses the air from the intake..??

I dont know if thats the intent or not, but I do know of all the times Ive seen it, which is several, it has never been open.

[335stoner]

I also have never seen one open

I believe they work under thermal conditions. as cold air passes over the spring it causes it to compress, then as the box heat soaks it will relax and closes. so when the car is off it will always be closed to you don't get any extra critters living in your air box.

here is a video I found