another 'what's knocking?' thread.....

[jack_kemp]

Morning everyone,

Just a quick question, I've just got my 172 cup, and it's making a knocking noise...

It only happens at high rpm in 1st and 2nd gear, but on all road surfaces, cornering or straight. It sounds like an exhaust knocking, but it's difficult to tell where it's coming from when inside the car.

I've checked the underside of the car for any obvious signs that something is knocking but I can't find anything.

Anyone had this problem?

 

[jack_kemp]

Forgot to add.... I've checked the engine and gearbox mounts.... it's neither of these.

 

[Will.]

Exhaust mount maybe? They are w**k.

 

[jack_kemp]

Exhaust mount maybe? They are w**k.

Haven't checked those.... will do tomorrow. It has a k-tec stealth system so i guess the increased pipe diameter makes it prone to knocking too.

 

[Curtis!]

Your whole f**king car probably!

 

[jack_kemp]

Your whole f**king car probably!

Oh yeah..... :S
Maybe it's the guy I've trapped in the boot....

 

[Damo_Sport]

Dogbone mount?

 

[jack_kemp]

Dogbone mount?

I've had a look, and it doesn't visibly look broken, but I'm running out of ideas so I think I'll get the k-tec uprated ones anyway.

 

[Budgie]

If it's at high revs in first and second, i'd bet pretty much anything on engine mounts.

Check they're all tight, but it's most likely the dogbone.

 

[Damo_Sport]

It wont look broken.. It will just be all squishy and crap... dogbones are easy to replace and cheap to buy

 

[quik99]

It will be your engine mounts, just done mine on my car because i had exactly the same problem! the mounts didnt look bad at all but after replacing the dogbone bushes with powerflex ones and doing the lower gearbox mount its made a HUGE difference! still need to do the two upper mounts then it will be perfect

 

[daddycool]

the knocking is the manifold hitting the subframe. have a look down the back of your engine and you will see the manifold just above the subframe, try and get a finger between the joint and the subframe- bet you can't!!

replacing the dogbone bush won't necessarily fix it. i actually got this problem AFTER i replaced the dogbone bush (for a powerflex one). check to make sure the lower bolt (viewable from under the arch with the wheel off) of the upper gearbox mount (under the battery) is tight as these can work lose. after that, its upto you what you replace first. search for exhaust knocking, it's a relatively common problem.

 

[daddycool]

It will be your engine mounts, just done mine on my car because i had exactly the same problem! the mounts didnt look bad at all but after replacing the dogbone bushes with powerflex ones and doing the lower gearbox mount its made a HUGE difference! still need to do the two upper mounts then it will be perfect

interesting that you got good results from replacing the lower gearbox mount. many say not to bother replacing this, but i might look into it if you got positive results.

 

[quik99]

interesting that you got good results from replacing the lower gearbox mount. many say not to bother replacing this, but i might look into it if you got positive results.

Yeah its made a big difference, i still get a tiny bit of knocking if really booting it in second at about 5k revs but its not as bad as it was. I put this down to the upper gearbox and engine mount needing to be replaced. The original mounts on my car where either very worn or they are built like crap because im not convinced that replacing with just standard mounts would cure the manifold knocking!