My 1989 320i has developed an engine knocking/ tapping noise. The noise occurs at about 1000rpm under light and hard acceleration. it does not happen at idle for anywhere above 1100rpm regardless of how hard I accelerate. The noise seems to be coming from the front of the engine near either the first inlet or something else around there. The noise is like a metallic rattle, possibly like a valve being knocked around due to a mistimed explosion, or just a piece of metal rattling.
The noise is still there after servicing and after a fuel injector cleaner put in the fuel tank.
Any suggestions on what this is? Is it timing or value clearances or a stuffed engine and time to transplant a 325?
engine knock / tap at low revs advice sought
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Grrrmachine
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Simplest thing to do is to get the rocker cover off and have a look at the valve train - about ten M8 nuts and a jubilee clip is what's holding it on.
Inside, I wouldn't be surprised to see a broken rocker arm. However, if all is good there you might be "lucky" and find that it's a broken exhaust stud. The engine won't be toast, but it's a royal PITA to fix.
Inside, I wouldn't be surprised to see a broken rocker arm. However, if all is good there you might be "lucky" and find that it's a broken exhaust stud. The engine won't be toast, but it's a royal PITA to fix.
'89 325i Touring | Touring Resto Thread | In-Dash Screen install
Good news, there is not broken rocker arm.
Bad news, there is a broken exhaust manifold stud. Even better news I managed to slip on a nut over the 1mm of thread that was protruding and tighten it nicely. Very quickly followed by more bad news as I tried to make sure the bolt next to it was tight and it snapped off with only light torque applied.
I used the search engine a bit and came across stories of removing the head, welding and other stuff that requires talent and time.
But then I came across a post from Brianmooooore in 2005. It suggested taking the manifold off and removing all the studs by using two nuts tightened against eachother and inserting new studs. Sounds fairly simple even for a chump like me.
Is it that easy?
Isn’t there just some magic glue I can shove on to make the problem go away?
Bad news, there is a broken exhaust manifold stud. Even better news I managed to slip on a nut over the 1mm of thread that was protruding and tighten it nicely. Very quickly followed by more bad news as I tried to make sure the bolt next to it was tight and it snapped off with only light torque applied.
I used the search engine a bit and came across stories of removing the head, welding and other stuff that requires talent and time.
But then I came across a post from Brianmooooore in 2005. It suggested taking the manifold off and removing all the studs by using two nuts tightened against eachother and inserting new studs. Sounds fairly simple even for a chump like me.
Is it that easy?
Isn’t there just some magic glue I can shove on to make the problem go away?
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daimlerman
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The good news is that this is at the front of the engine,where access is a little easier than at,say,number 6!
Two nuts locked together may well work,but soak the broken stud in penetrating oil(WD40 or similar)overnight first.
Next stage is to attempt to weld a nut over the remains of the stud,the heat generated by welding helps to loosen the corrosion as well as allowing a slightly bigger tool to be used.
The last hope is to drill the bloody thing out....
Two nuts locked together may well work,but soak the broken stud in penetrating oil(WD40 or similar)overnight first.
Next stage is to attempt to weld a nut over the remains of the stud,the heat generated by welding helps to loosen the corrosion as well as allowing a slightly bigger tool to be used.
The last hope is to drill the bloody thing out....
Youth is wasted on the young.
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Grrrmachine
- E30 Zone Wiki / Team Member
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Get yourself one of these - costs about a fiver:
and it runs on lighter fluid (available in special pressurised cans). As Daimlerman says, the day before, or even for the whole week prior to removing the offending manifold, soak each and every exhaust stud and nut in penetrating oil. Give them all a dose every evening.
Then when you come to remove the manifold, get each nut undone, even if it means breaking them. Once you've got access to the studs, wind on two nuts as per Brianmoooore's method. Then use your butane torch (pictured) to get the stud properly hot - it won't glow cherry red, but a minute of flame will make it toasty. Then try and crack the stud off using the two nuts.
It may also be worth investing in a die set to clean up the threads on the broken studs prior to removing them:
and it runs on lighter fluid (available in special pressurised cans). As Daimlerman says, the day before, or even for the whole week prior to removing the offending manifold, soak each and every exhaust stud and nut in penetrating oil. Give them all a dose every evening.
Then when you come to remove the manifold, get each nut undone, even if it means breaking them. Once you've got access to the studs, wind on two nuts as per Brianmoooore's method. Then use your butane torch (pictured) to get the stud properly hot - it won't glow cherry red, but a minute of flame will make it toasty. Then try and crack the stud off using the two nuts.
It may also be worth investing in a die set to clean up the threads on the broken studs prior to removing them:
'89 325i Touring | Touring Resto Thread | In-Dash Screen install