Front Subframe replacement

[Tinkley]

Well I suppose it had to happen!. Large pothole has done for wheel and front subframe. With the front strut angled back with only just enough clearance to get home it looks a bit serious. Daylight reveals full horrors of yesterday evenings wheel changing in the dark after hitting aforementioned pothole. Had hoped it was just a bent track rod but lack of 'suspension' (none) hinted otherwise. Looks like there was internal rusting of the subframe as the 'oily' exterior shows no signs of corrosion. I had cleaned it up when changing engines over.

How hard is it to change the subframe? I have one on my old car (engine/trans out) which I could swap if its not too bad to do. Only car stands, no ramps so might be a bit more tricky. The Haynes doesn't really cover this part well but I am reluctant to scrap her yet. New spheres are not an issue until the strut is vertical!.

Any hints, tips appreciated. Oh and are new/secondhand subframes available. Is Kitch's 16v subframe the same as for a 1.6 petrol? and is it available off of GSEG?.

[Tim Leech]

All BX subframes are the same, but rust issues are common, from memory the G-SEG was quite patchy anyway and had been welded up.

Someone must have one.....

[Thread Bear]

This is the very job I have to do to Walt. My bud was showing off the BX abilities to rise to the occasion in a ford to his girlfriend. Sadly it all went horribly wrong when he ran the car into the eroded other side of the ford and bent the front suspension. His girlfriend rose to the occasion by calling him a git etc and he had to change the wheel in the river . Very little rising of any sort after that and I bought the wreckage of a mint 70k miler back . What a waste of a bargain at £650 bought in, scrap value out . He is now driving one of the last CX 2.5 Diesel Safari and using it as a van till it fails, I fear.

So far most folk have said take the engine out as so many hydraulic pipes are attached in some way to the subframe it would be all to easy to miss one and tear a pipe out. In theory, though, one ought to be able to do it from underneath, though the engine might need to be supported from above. Looking at Walt I guess engine out makes sense as I can do the cam belt etc and change the octopus etc all in one go. Of course Walt is otherwise a cracking car that needs conserving for the future and the effort will in all probability cover the cost of doing the work long term. I have a good cross-member I bought from a very interesting guy from very near Beaconsfield. This all waits till I have my workshop built. Your situation might not be quite so fiscally clear cut.

Hopefully the pot hole was logged by the council, as if so, you should claim.

[mat_fenwick]

Ramps would be of little help with the wheels off...

It's not a job I've done, but it looks simple enough. If you remove the good spare one first as access will be easier with no engine, you'll know what needs to be removed from it and the job is always easier second time around. I use cut down logs as axle stands as I feel more confident underneath it that way - we have no hard standing so I'm always worried about the legs sinking in. The more knottier they are the less chance of splitting!

The only attachment that the engine has to the subframe is the lower mount, and all that does is prevent fore/aft twisting of the engine. It will hang perfectly happily on the other two mounts.

[Tinkley]

Thanks guys. TB I'm not sure it needs engine out as only the bottom 'stabiliser' av mount needs be disconnected. With the donor car (no engine) I can forsee the only major problem is the hard bundy brake pipe feeds that will need to be disconnected each end. The rest should be OK - at least on the donor!. The octopus retainers straps etc are all fairly easily visible on the donor so just mapping them should suffice.

Dead right Mat it will make the 2nd one easier once you know the routine

On the runner I anticipate a problem with the anti roll bar bolt which is bent 5° or the inner wing/chassis is too if I'm lucky. Making a wedge is OK on replacement, if it is still vertical on chassis. It does not look like the strut top mount has twisted but there was a tell tale hiss of pressure when I pumped it up to max height and took the wheel off.... just misalignment I hope that the rubber will absorb. Not a deal breaker.

Thinking back on the incident, it could be that the subframe bent prior to the wheel going as it threw the car hard right almost into tree. Fortunately only 20mph 3rd gear returning from a walk around Frensham Little Pond. Considering I nearly went to Stratford to meet you great guys and gals on this forum in the flesh (apologies for not getting there) it could have been much worse. In fact the idea at 70 does not bear contemplating... my route would have been 287, M3, 339, 34, M40 then Stratty, mainly 50-70mph stuff and quite twisty prior to Newbury. There really was very very little rust on the frame externally and I think its the side weld towards the rear that has been the main fail point.

You may find as I did a post from oilyspanner who reckoned you could do it in 20 minutes mmmm Well I can't Probably drop the wishbones and it would be worth changing the bushes if I can persuade the wretched pins out. I watched Marcus change one for me at PTS but he just hacksawed through the pin and used a new one. I do have a spare pin and one set of bushes, and they are cheap enough but the pin is hard to find. It's called an 'Axe de bras avant' in French BTW - you get some interesting results from google when you enter that

I don't think Surrey 'log' potholes as they are genuinely the worst maintained roads in the country. Partner has done 2 or 3 tyres on the C4, just guage the hole depth when its full of water. Worst are about one foot deep, best about 2". Try the Elstead to Farnham road near Tilford. Even with 17 or 19" wheels and high aspect ratio tyres it is going to shake you!. Many unmetalled roads are smoother. They also turn down 99% of claims if you check the data for council payouts. Worst road I know in London is Stamford Street on the South Bank which sinks like crazy after heavy rain and frosts!.

[RxBX]

All BX subframes are the same, but rust issues are common, from memory the G-SEG was quite patchy anyway and had been welded up.

Someone must have one.....

Tim, That is NOT true (I've broken up enough BX's to know) early subframes are totally incompatible to the later design due to the spindles sizes !

Take look at the Haynes manual (The old thick one numbered 908) pages 229/230 showing the tapered roller bearing and then go to the revision/supplement section on page 396 at the bottom of the page (section17) and then on to page 397 which shows you the cross-section of the two type of configuration !

The early MK1's had bearing's fitted into the subframes with wishbone spindles of 14mm Dia, so therefore the front wishbone/bushes are different too to the later set-up !

Then some later MK1 had the revised design fitted to them, as have ALL the MK2's which had larger 16mm dia. wishbone spindles !

It's all been covered before (I've even discussed this with you on journeys in a car to rallies or on the phone in the past) also IIRC you MK1 GT has this set-up so I'm a bit surprised with your quote, THIS thread should be of help too

.

[KevR]

Probably drop the wishbones and it would be worth changing the bushes if I can persuade the wretched pins out. I watched Marcus change one for me at PTS but he just hacksawed through the pin and used a new one. I do have a spare pin and one set of bushes, and they are cheap enough but the pin is hard to find. It's called an 'Axe de bras avant' in French BTW - you get some interesting results from google when you enter that

I've done the wishbone bushes on both cars recently, as well as removing the wishbones from a scrapper, and once I'd worked out how to withdraw the pins using a variety of sleeves so the front nut can be used to pull the pin out, they haven't been a problem. There's been no discernible wear on the pins either. I've got at least one NOS one on the shelf but haven't bothered fitting it as the originals were fine.

When you do the subframe change, you'll find you need a deep socket to get at the nuts under the floor on each side - and typical Citroen, it's an odd size (18mm from memory). Best to check that and make sure you have the right one before starting!

Oh, and when you refit the wishbones, don't tighten the nuts up 'til the car's back on its wheels and suspension at normal height.

[Kitch]

G-SEG's subframe is a bit of a patchwork quilt, but I've said I've reserved it for one of the guys on the 16v forum. Haven't heard back from him though, so if he doesn't want it you can.

[Vanny]

All BX subframes are the same, but rust issues are common, from memory the G-SEG was quite patchy anyway and had been welded up.

Someone must have one.....

Tim, That is NOT true

Pretty sure the 4x4 ones are different as well.



I just can't imagine how a subframe can shift that far and not destroy the body. Even if it was a rather crusty and past best subframe, to move as much as it sounds like this one has, it must have damaged the shell somewhere.

[Thread Bear]

That is the way I read it. Only the bottom mount on the engine. If it were not for all the pipes, valve and height adjuster it would be a pretty easy task. If you know your way about then even that is not a biggy. For me I would need to label some of the pipes to get it back together correctly.

I was looking to rebuild the wishbones before fitting as it seems silly not to on my project. Its another bench job for a sorted out workshop though, really.

[Tinkley]

The subframe has twisted from the anti roll bar forward bolt. Lower down the front end of the wishbone is down quite a bit, and behind there is a significant crease, complete with nice open hole feature. Probably 45-50mm of crease...which is why the tyre was rubbing on the back of the wheel arch. Had it been daytime or I had had a torch I might have got it taken back. It happened on a road I know very well so it was quite a surprise, might even have been rubbish left in the road as a lot of 'kids' use it at times and fly tipping is not exactly unknown in the area. If its damaged the shell its in the area with the anti roll bar monting bolt (forward one). The anti roll bar has 5° of twist on the offside, unlike the donor.

Imagine the front wheel being pushed backwards until the strut is 5° from vertical at base (in hub) that's about what it looks like. When the car is mobile I will triple check the exact location including deep into the verges. Odd thing it being the offside as I was concentrating on the nearside, being a sharp right hand bend.

Thanks for the tip on the 18mm socket. My ancient Kamasa (circa 1975) set has done OK so far, only had to borrow a 35mm for the hub nuts!.

[RobC]

While we're on the subject, 16v rear subframes are different as well (I know from bitter experience...)

[Way2go]

The subframe has twisted from the anti roll bar forward bolt. Lower down the front end of the wishbone is down quite a bit, and behind there is a significant crease, complete with nice open hole feature. Probably 45-50mm of crease...which is why the tyre was rubbing on the back of the wheel arch.

Surely there must have been a pre-existing weakness in the subframe for this to occur? We encounter potholes, road humps and cushions on a frequent basis without more than mild discomfort in a hydro-pneumatic BX but admittedly the anti-car lobby is making them worse. We even have "Sump-Breakers" installed in dedicated bus lanes here. I think the BX in intermediate may clear them but I'm not taking the chance as if these don't get you, the camera's will!

[Tinkley]

Here's a few pics of the condition

1. The wheel, the tyre is OK!.

http://s23.postimg.org/e4s9crpqz/wheel_4.jpg" onclick="window.open(this.href);return false;

2. Where the wheel sits, too far back.

http://s16.postimg.org/bgu6b1hs5/wheel_1.jpg" onclick="window.open(this.href);return false;

3. Damage to subframe.

http://s18.postimg.org/f3zget61l/wheel_2.jpg" onclick="window.open(this.href);return false;

4. Strut angle.

http://s24.postimg.org/mvhbjlmgl/wheel_3.jpg" onclick="window.open(this.href);return false;

[KevR]

Surely there must have been a pre-existing weakness in the subframe for this to occur?

Yep - the subframes tend to rust from the inside out, in particular blowing out the side seams, so they're significantly weakened long before you see any problem on the outside.