Long (subframe lowering) Bolts. How to use them?

[tolsen]

By the way, you won't get much better access by lowering subframe since it will still block access. Perhaps better to drop engine and transmission on one side at the time as required.

[Thrumbleux]

I would definitely fit stainless steel bolts. Available from Toolstation for a small fee. Only GBP 2.68 for fifty M6 x 20 cap screws. How much did Smart charge?

Bought a heap of them from Screwfix. And they will be well coated with waterproof grease on installation.

[Thrumbleux]

By the way, you won't get much better access by lowering subframe since it will still block access. Perhaps better to drop engine and transmission on one side at the time as required.

But I'll better access the front engine mount then I'll have the choice of all three mounts to lower the engine from. I'm hoping swinging it back (front mount removed) will let me get the job done. It's access to the bolts on the front leading edge of the sump I struggled with when I attempted it before.

[cougar7609]

Looking at what you wanting to do and having replaced the sump on my car before to fit one with a drain hole. I didnt use the bolts for this job, I just raised up the car on axle stands so it was high enough to slide under the car and then slid under it and undid the bolts for the sump. You need a couple of extensions for your rachet but you can undo the bolts pretty much all of the way around. I had a problem with one or two but eventually got them undone and so replaced it without much hassle at all.

[Thrumbleux]

Struggling to find the torque setting for the subframe to chassis bolts - is there one?
Or what do you guys re-torque to?

[tolsen]

The subframe bolts are M6 so can't be torqued up with a torque wrench unless you have one that goes low enough.

Max 12 Nm for 8.8 bolts. No more than 10 Nm for A2 or A4 stainless.

Lowest torque setting of most 1/2 inch drive torque wrenches is 20 - 30 Nm.

Just tighten them up by feel or angle turn. Sump bolt torque is not critical.


Something went wrong with own my ecu when I wrote that. I was thinking of sump bolts. Cannot figure out why I wrote subframe bolts.

[Thrumbleux]

The subframe bolts are M6 .
.

The subframe bolts are M12.

[Thrumbleux]

Long bolts work well - and quick - once the car is jacked, which takes a bit of time to do at both ends.
How sensitive are the long bolts to the car being a little off level, ie nose down?
I still want to replace the thermostat but by the look of things I'll need the car on the road before I can get the parts I need, so it'll have to be propped up all over again.
Given that I have 100mm spacers on the bolts so not dropping the full amount, is it viable to raise the rear only and only high enough to drop the few inches and still have no problems when I come to raise the subframe back to meet the chassis (the slight angle concerns me). It would save me a shed load of time if I could. Any idea anyone?

[bob-in-dav]

You seem to be making extra work for yourself here.

If you just want to get better access to the bottom end of the breather pipe and front face of the engine, (which is easier on a fortwo than a roadster) you can just remove the crossways bolt in the front engine mounting with a jack under the engine of course to control lowering.

If you are a paid up member of Evilution, there's a guide on using the drop bolts -http://www.evilution.co.uk/index.php?menu=info&mod=650

[Thrumbleux]

Nah, breather pipe isn't a concern anymore - thermostat is next on the list.
I have the bolts now and given how much space they create for certain jobs seems crazy not to benefit from them as much as possible. It's the jacking the car at both ends that's the PITA.
And the front engine mount is a pig to access.

[tolsen]

Struggling to find the torque setting for the subframe to chassis bolts - is there one?
Or what do you guys re-torque to?

Recommended torque is 85 Nm according to my notes. Can't remember where I got it. Remember to torque in right sequence starting with port forward, then starboard forward and finally any of the two rear.

[Thrumbleux]

Cheers TK.
Given they are the same size as wheel bolts I was going to pull them to 110N.m but 85 lubed sounds better.

[Smartie81]

When people remove the engine, I understand its good to use longer bolts, to lower the subframe. Would it be possible to not just purchase a piece of studding from screwfix or toolsatation, with two nuts on the end?

[Thrumbleux]

When people remove the engine, I understand its good to use longer bolts, to lower the subframe.

They allow much better - make that actual - access to the front of the engine block. In nine years of working on my smart I first saw its starter motor last week - courtesy of the long bolts.

Would it be possible to not just purchase a piece of studding from screwfix or toolsatation, with two nuts on the end?

That would drop the subframe for sure, but if the threads snagged on re-raising it it could be pig to get back into place. For me it's not worth the risk with so much weight to relocate. The bolts are smooth where the subframe passes over them so snagging can't happen.
Bought now, the £30 or so they cost me isn't grudged. Changing the thermostat (next job on the list) should be a breeze, and I no longer live in mortal fear of the starter or alternator needing attention.
View the bolts as tools and decide from there if you want them in your tool box.

[tolsen]

M12 threaded bar from Screwfix has 1.75 mm pitch. Subframe bolts and lowering bolts have 1.5 mm pitch.