gaz_gaz
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| posted on 22/3/14 at 07:04 AM |
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BMW and there infamous cracking manifolds
long and short of it is..
About a lifetime ago my 525d suddenly lost 10mpg, became really laggy and started to stink of fumes in the cabin when idling.
The give away signs of a cracked exhaust manifold. Google search confirmed I wasn't alone and that this was a common problem on cars reaching
the 90k mile mark
After nearly a year of putting it off, I decided it was time to do something about it
Out came the spanners and off came the knuckle skin but the end result was the exhaust manifold sat on the bench.
So that's where my boost and MPG has gone.
What gets me is that since I've had the car. I've had and repaired every single "common fault".
It was a well looked after FSH single owner car when I bought it.
Surely all these "common problems" should be remedied by BMW if there happening to almost every car?
I was thinking of writting to them but I feel it'll fall on deaf ears?
what do you guys think?
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mangogrooveworkshop
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| posted on 22/3/14 at 08:10 AM |
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My take is the hot cold cycles exceeded the design of the metallic form. Just replace and move on. Its lasted all this time. My theory is that theres
no flexi between the exhaust and this component. so all the movement on the exhaust has a lever action on a solid item that is bolted between two
moving items. Have you checked the rubber engine mounts for excessive movement. FWD cars then to break the exhaust under the engine if the mounts are
soft.
with old cars that we run we just sort and replace stuff that stops it moving forward. Worrying about long time design issues is for the birds. They
are in the business of making money..... and they are seldom interested beyond the first ownership phase Ie Ist owner or company car fleet ect.
So get the rods and weld it with a stick welder or cough for the new part .....or breakers unobtainum.
I just run what ever crap car i get cheap. As long as it starts and runs it gets driven to the edge of its economic life
The sevens however get the best as i hate breaking down in them.
[Edited on 22-3-14 by mangogrooveworkshop]
[Edited on 22-3-14 by mangogrooveworkshop]
[Edited on 22-3-14 by mangogrooveworkshop]
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MikeRJ
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| posted on 22/3/14 at 08:22 AM |
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I managed to repair a cracked cast manifold on my Fiat Coupe 20V turbo using a MIG. Not ideal, but it lasted a good 45k miles until I sold it.
I firstly cleaned it up and Vee'd the cracks with a angle grinder (used Dremel for difficult to reach bits). Then I got it as hot as I could in
an oven to start with, and then left a blow lamp pointed down the affected exhaust port to keep it as hot as possible whilst I welded it up.
Afterwards I covered it an old fire blanket to let it cool down slowly.
[Edited on 22/3/14 by MikeRJ]
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Peteff
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| posted on 22/3/14 at 08:34 AM |
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Honda 2.2 Accord had the same problem, they did a warranty recall on them up to 100,000 miles or so many years and they look a bitch to get at.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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adithorp
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| posted on 22/3/14 at 08:48 AM |
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Thats a huge crack...Oh hang on, it's just a HUGE PHOTO!
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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gaz_gaz
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| posted on 22/3/14 at 09:01 AM |
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the repair is straight forwardfor me.
I'm fitting a cast iron manifold from an e39 diesel which should rectify for good.
access is an absolute nightmare.
in there wisdom bmw designed the rocker cover and airfilter housing as 1 piece so you have to remove inlet manifold. injectors. egr pipework ect to
get propr access then a millon rocker cover bolts.
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Simon
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| posted on 22/3/14 at 09:47 AM |
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Yep, £150/hour. Simple really 
ATB
Simon
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snapper
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| posted on 22/3/14 at 10:06 AM |
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A flexi section in exhaust may help
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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MikeRJ
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| posted on 22/3/14 at 12:28 PM |
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quote:
Originally posted by snapper
A flexi section in exhaust may help
This is a purely thermal issue rather than stress induced from the engine moving around. There's a long and very rigid manifold, cast from a
non ductile material that gets heated to extreme temperatures and wants to expand in all directions, but it's rigidly clamped to an even stiffer
casting (the cylinder head) so very large stresses are generated. Micro cracks within the casting grow every time the manifold is heat cycled.
The longer the manifold the worse the problem, so five and six cylinder engines tend to suffer more than four pots.
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coyoteboy
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| posted on 24/3/14 at 07:09 PM |
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Seen the plastic intakemanis fail too.
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