Is it normal for a MacPherson strut top mount to have a ton of slack?

[rcx132]

My wife's Astra 2003 has had a knocking sound coming from somewhere around the suspension. I had a search for the problem and noticed that the MacPherson struts have 4mm of slack at the top where they connect to the "towers" on the body. The nuts were fully done up so I assumed the rubber mounts must have worn and caused the slack/gap. I replaced the entire top mounts on both struts and now there's an even bigger gap! Wierd. I may need to find an Astra forum and ask what could be going on.

The third photo shows the whole new top mounts I fitted.

 

[Munkul]

That's normal. The top cap is only there to keep the strut attached to the car if the rubber joint below fails completely.

Did it cure the knocking?

 

[m_c]

That's pretty normal.
Main thing is there is no excessive sideways movement with the weight removed from the suspension and the wheel/strut shaken, although there are some vehicles where movement is normal.

Knocking is far more likely to be a ball joint or bush.

 

[Blobber]

Yep normal for them, infact I think there is a note come up for the MOT testers informing them of the fact that there will be play in the top mounts, check the anti roll bar links as thats very common to give a knocking on the suspension and cheap as chips to replace

 

[MetalMonkey]

Normal for those, the Corsa ones are the same, they seat in the tower once the weight is on them.

 

[T5 TDI]

Some Polo's too. The MOT testers are told to jack under the the suspension which should take the slack out. Anti-roll links for a rattle over bumps and ball joints if it is a single clonk. There are other things of course like bushes and any loose bolts (rack, etc).

 

[tom2207]

drop links would be my starting point .

 

[striker]

Ive had a knock on my Berlingo front since Ive owned it, 3yrs. I've told the mot inspector 3yrs in a row to look for it. He says nothing wrong everything is rock solid. Ive changed drop links, anti roll bar bushes, track rod ends. I've had pry bars in the bottom arms, I can't find any play anywhere. It's a knock that happens over high frequency bumps like broken road surfaces, fine over pot holes and speed bumps. I think it's shocker or top mount related. I have some top mounts to go on, when I have the springs off the struts I will check them for any play and change the struts at the same time. If that doesn't sort it, then I'm stumped!!

 

[James1979]

Ive had a knock on my Berlingo front since Ive owned it, 3yrs. I've told the mot inspector 3yrs in a row to look for it. He says nothing wrong everything is rock solid. Ive changed drop links, anti roll bar bushes, track rod ends. I've had pry bars in the bottom arms, I can't find any play anywhere. It's a knock that happens over high frequency bumps like broken road surfaces, fine over pot holes and speed bumps. I think it's shocker or top mount related. I have some top mounts to go on, when I have the springs off the struts I will check them for any play and change the struts at the same time. If that doesn't sort it, then I'm stumped!!

Try and find a garage that has shaker plates and get them to put it on there?

They show up all sorts of stuff the traditional bar tests won’t.

 

[Anguz]

Try and find a garage that has shaker plates and get them to put it on there?

They show up all sorts of stuff the traditional bar tests won’t.

My kit car mot involved these on saturday. I know its no worse than what i do to it on the road, but it does look cruel to the car

 

[James1979]

My kit car mot involved these on saturday. I know its no worse than what i do to it on the road, but it does look cruel to the car

It’s really harsh looking but it finds loads of faults.

Don’t use HGV ones on a agila son of the haulier I do for found that out the hard way!!

 

[pedrobedro]

I've had a knock on my Berlingo front since Ive owned it, 3yrs. I've told the mot inspector 3yrs in a row to look for it. He says nothing wrong everything is rock solid. Ive changed drop links, anti roll bar bushes, track rod ends. I've had pry bars in the bottom arms, I can't find any play anywhere. It's a knock that happens over high frequency bumps like broken road surfaces, fine over pot holes and speed bumps. I think it's shocker or top mount related. I have some top mounts to go on, when I have the springs off the struts I will check them for any play and change the struts at the same time. If that doesn't sort it, then I'm stumped!!

Ours has a knock when turning at low speed, usually just one clunk. Last time it was a broken spring right near the bottom coil and it was not visible till it went on the hoist. I fitted new springs a couple of years ago but it still clunks now. MOT passed no problem and the top bearings which were suspect are still good so just ignore it and let it develop.

 

[striker]

Ours has a knock when turning at low speed, usually just one clunk. Last time it was a broken spring right near the bottom coil and it was not visible till it went on the hoist. I fitted new springs a couple of years ago but it still clunks now. MOT passed no problem and the top bearings which were suspect are still good so just ignore it and let it develop.

Checked springs, all good. It's been developing for 3 years!!! It's driving me mad!

 

[rcx132]

Thanks for all the tips. So I wasted £50 and an afternoons work oh well. When you say it could be the ball joint causing the knocking, would that be steering rod ends?

 

[striker]

Start with cheapest first, drop links and track rod ends. Mind you neither cured my Berlingo. You can feel wear in track rod ends if you get someone to turn steering wheel back and forth, just a little to take up slack whilst you look at them and feel with your hand, worn drop links are more of a rattle over bumps.

 

[T5 TDI]

Checked springs, all good. It's been developing for 3 years!!! It's driving me mad!

I'm with Pedro, sometimes the springs fractures are impossible to see especially if the spring doesn't move at the break. I had a little Peugeot van doing that once, the break was on the spring tail at the bottom. You could feel with your fingers but you couldn't see it. That one gave a single knock on 3 point turns or sharp slow corners.

 

[stuvy]

My mx5 had a broken spring and it was right at the very top and you couldn’t see it

Are you getting any feed back through the steering wheel or brake pedal when the knock happens?

 

[striker]

No, nothing felt through the steering wheel.

 

[stuvy]

No, nothing felt through the steering wheel.

Brake pedal?

We had a front caliper that wasn’t closing and retracting on one side and made us chase a noise for ages under very very light braking you could hear the nose stop as it was the worn pad slapping the disc

 

[striker]

Can't feel anything through the brake pedal