408 front subframe / crossmember removal
 

I need to get my front subframe out for repair. Anybody done this on a V8 car? I am really looking for advice on any issues or tips on doing this. A lot towards the end of the list will have to be done from under the car.

I am thinking it goes something like this:

• remove bumper and apron
• remove undertray and decking bearing the builders plate at the front of the engine compartment
• remove electric fans
• drain coolant and remove radiator
• disconnect and plug brake lines
• remove shocks
• remove springs (extremely carefully!!!)
• probably will remove wishbones while I am there
• disconnect steering (any advice on how to do this wanted especially, please)
• Remove tubular frame supporting front bodywork
• remove bolts attaching subframe to each side of wheelwell bodywork
• remove bolts attaching subframe to the front ends of the frame rails and lower.

Have I missed anything? Any obvious pitfalls? I know proper shops often cut and reweld that front tubular framework but I really hope to avoid that.

Any advice will be appreciated.

Thanks

David

Hi David,

I think you got it pretty well sorted. I just did this job about 8 weeks ago.

My advice:

Take photos of everything, specially about the position of the washers on the wishbone mountings. Don’t mix them up, put them in labeled plastic bags.

To remove the steering is straightforward. First, while the subframe is still in place , remove the steering arm from the steering box. Everything else is really logical.

No need to cut and weld anything, at least on the 411.(sorry, but in my opinion someone who does this „cutting and welding“ is just to lazy to do a good job).

While doing this subframe removal I suggest that you inspect and if necessary replace all metalastic bushes etc. I send all parts to be bead blasted and repainted. You will never be able to access all the parts so easily again.

After finishing don‘t forget to have the track aligned.

I have attached some pictures of the job I have done.

Regards

Thomas
.

Thomas, thank you for your informative reply. It's very reassuring to know I am on the right track.

David

Thomas a great job. I noticed the Spax Shock Absorber do you also have them on the rear of the car ? I would much appreciate the numbers of both and any experience you have had with them. Did you consider Koni and would you have a listing on those as well. My 411 has aftermarket gas units on the back which you pump up with compressed air to compensate for the disconnected self levelling system. You unfortunately need to pump them up regularly as they do not hold pressure very well.

Regards Peter Dowdle

Thomas, to help me plan, do you have any estimate of that crossmember's weight, please?

David

Hi David,

I would estimate that the bare crossmember, without any suspension or steering components, weights around 25-30 Kg. I was just about able to carry it all by myself, but preferred a helping hand to put it on the workbench.

Regards

Thomas

Hi Peter,

I have no experience on the Spax units, as the car is still lacking it’s drive train. The part numbers can be found in my parts list in the resource section.
Yes, I fitted new Spax shocks also to the rear.

Regards

Thomas

Thank you, Thomas.

David

David,
While you have got the suspension disassembled I suggest you examine the bolt holes in spring seat pans for stress cracks.

I would also recommend that you mark the fulcrum brackets and scribe their position on the crossmember before removal

Assuming the suspension hasn't been rebuilt in the recent past, the wedge/distance pieces which sit on top of the springs may need replacing along with the steel and rubber rings used to isolate the coil springs.

Bristol Cars Services recommended using new turret nuts when re-fitting the wishbones (they are a special half-height turret nut).

I wrote a few posts about my experience with the front suspension which you might find helpful http://www.bristolcars.info/forums/8...uspension.html

Regards,

Kevin

Thanks, Kevin. All helpful except the flat area where the fulcrum brackets sit is rusted away. That's why the whole subframe has to come out for repair. Odd place to have rusted but that's the way it is.

I made a start stripping the parts today. Righthand shock and spring are out. I will check the pans as you suggest.

David

Here's a picture of the rusted area on my subframe.

David

I can confirm this! After sandblasting the spring pans, one had rust damage and both had stress cracks as described. I cut out all damage and reinforced the spring pans with new material on the stress points.

Regards

Thomas

I took the second spring out today.

I looked at the spring pans. They need proper cleanup that may reveal cracks but I could see no sign of any today. Amazingly, the lower spring seats both seem to be reusable. The upper wedges and spring seats are just not there at all. I do have new ones to fit when I reassemble.

Try as I might, I could not get the spring pan to lower staying parallel to the wishbones (see pic) but it came down ok anyway.

I know the Spax part numbers for shocks but can anybody identify this Koni that was fitted?

David

Hi David,

My 411S5 was equipped with the same Koni shock absorbers. Maybe it is still the original, factory fitted, shock. I searched the internet today, but could not find any reference about Bristol and Koni shocks.

Looking at your spring pan, I can see some corrosion around the center hole. Get it sandblasted and then repair it. The spring pan is made from a two layer steel material and moisture can penetrate between the two steel layers.

Regards

Thomas

Wow, that's pretty serious corrosion!

Probably because the wedge distance pieces were missing, so there would be more pressure on one side of the spring.

Assuming the surviving lower spring seats are made of the same material as the upper wedge distance pieces, (they would have been orignally), then it is likely they have been replaced at some stage.

Do you know much about the history of the car?


Kevin

Yes, that rust is bad and in a strange place. John Tullett says it must be from mud sat there for a long time. It's actually hard to see in there which is why I think it has been undiscovered over the years. I only found it investigating the upper spring supports and even then only by accident.

The car is 408 Mk1 7023. Its history from leaving the factory to c.1990 is unknown to me. It was sat with no engine and transmission when Tony Crook took a prospective buyer to see it at somebody's house. The buyer was an Air Force Chaplain whom I have spoken to. He had the body restored and repainted in the UK in 1991. The work was not done by SLJ but they acted as project managers and I have various reports they sent on the restoration. The owner then brought the car with him when he moved to the Minnesota in 1992 and had a later 360 engine fitted with a period correct 727 gearbox.

The chaplain sold the car, I think around 2000, and it seems it had 2 other owners before me. It was in West Virginia in 2001. I bought the car here in Florida from a gentleman who had it from 2009. He did a lot of restoration on the brakes but not the springs, etc..

I suspect the rust was missed in the 1991 restoration but it could be from salt in Minnesota. So far, there doesn't seem to be any other rusty area to the frame or this subframe but I will keep checking and there may be more visible once the subframe is out.

David

David,
It is odd that the rust is only in one spot, however it is an area that could hold some water if there was mud there and particularly if the car was parked across a slope. Add salt to the scenario and it could do some serious damage over time. Of course once the rust takes hold it would just get worse every time the car was driven in wet weather.

I once lent someone a trailer who left it with inches of wet sand sitting in it for six months or more. It had almost completely rusted through the bottom of the trailer.

Anyway, it's good that you found it and can now restore it.

Another spot where the V8 cars are notorious for rust is around the top mounting points for the rear shock absorbers. Which is even harder to see!

Kevin

Thanks for that tip - I'll take a good look there.

David

Hi David,

as I replaced all the screws on the front axle, I made a list of them. Maybe this will help:

Quant Description Dimension lenght

8 Hex Screw 1/4-28 1/2
2 Hex Screw 1/2-20 1 1/4
4 Hex Screw 3/8-24 1
16 Hex Screw 3/8-24 1
10 Hex Screw 3/8-24 1
6 Hex Screw 5/16-24 3/4
8 Hex Screw 5/16-24 1


This is for my 411 S5, I do not know if earlier cars used BSF screws instead.

Regards

Thomas

Thank you, Thomas.

It seems, from the parts book, that nearly every nut and bolt on my 408 suspension is BSF. I can get those here in the US from a few suppliers but I would have thought several of the fasteners could be safely replaced with UNF Fine Thread equivalents.

E.g. the bolts holding the upper ball joint between the upper wishbones are listed as 1/2" BSF. So I may investigate using 1/2-20 Grade 8 to replace those. Provided the unthreaded portion of the UNF bolt is the same diameter as the BSF one, it should work. I'd be interested in peoples' opinions on that.

David

Thomas,
I'm pretty sure on my 411 S5 they were all still BSF.
Regards,
Kevin

David,
I thought this may be useful/interesting - it's a strength test comparison between BSF and UNF
https://reports.aerade.cranfield.ac....=1&isAllowed=y


Kevin

Thanks, Kevin. I think the UNF will be fine in most locations.

You may be interested to see my progress dismantling. I have done a bit each day for several days. Tomorrow, I hope to get the tubular cage out from the front of the car and the lower wishbones off. The upper wishbones are being a pain and may have to be removed after the crossmember comes out to get better access. I think I'll leave the oil cooler attached but hang it from the metal work

David

On my car definetly not. On the front subframe there was not a single BSF bolt. I collected all the original screws and measured them, then bought new ones. all UNF. Very strange...

I found a few BSf bolts on the rear axle and its suspension. But even the studs for the swingarm housings were UNF.

Definitely!

The bolts which go through the bushes in the wishbones are probably seized with rust. They were on my 411. It's very hard to tell until you go to remove them!

Thankfully on the 411 the fulcrum bracket arrangment and the way the wishbones are fixed to the crossmember is a little different, which makes it easier to get them out.

Good luck and please keep the photos coming!
Kevin

Well now you have got me wondering Thomas :) Maybe I am making assumptions! It was 20 years ago and I must admit I didn't measure every nut or bolt, and some of the work was done by a third party. I'll have to go back and look at what he supplied and what I bought from Bristol. I know for sure that the "thin turret nuts" that secure the upper wishbones to the crossmember were bought from Bristol and they were 1/2" BSF.

I was given the impression by Bristol at the time that many suspension parts carried through from the 407, 408 & 409 to the 410 and 411 (and probably the 412). Certainly many of the parts I bought from Bristol for my 411 had 407-409 part numbers.

Is it possible your car had already had restoration work done and someone had already replaced most the BSF nuts and bolts with UNF?

Regards,
Kevin

Darn! You got me… I was a bit over-enthusiastic in my statement „not a single BSF“. Yes the thin turret nuts are definitely BSF. I had these nuts glass-blasted and zink plated, so these were not on my list. Sorry for that..

Regards

Thomas

Just to let you know I am stalled for a bit trying to work out how to remove the overtightened, hard to access and oddly shallow bolts holding the crossmember to the front of the main chassis rails. We have guests for a few days too so I won't be touching the car until next week.

David

Progress. After many days of soaking the offending bolts with PB Blaster (penetrant), the 18 bolts holding the crossmember to the front of the frame rails have all been loosened ready for removal. The steering U-Joint has been disconnected from the steering box and the tubular frame ahead of the crossmember is all loosened up too.

One challenge remains before I try to actually remove the crossmember: there are bolts holding the inner fender wall to the top of the crossmember and, so far, I haven't got any of them out. There are 4 each side on the 408 (I think later cars only had 3) and they are partially hidden by a large ridge on the top of the crossbeam. It makes getting a socket on there impossible. So I will have to put a wrench there and use the socket inside except the clearances by the manifolds don't leave room for a socket there either on the rear two bolts each side! I attempted to cut the head off one bolt but I was trying to be sure I didn't cut the metal the bolt passes through and didn't cut far enough in so I cut the head, not the threaded neck!!!!

I think I'll be able to do it with help and a neighbour has offered to assist later this week.

David

Hi David,

I used an angle grinder with a thin disc to grind off the heads. Don’t worry about the sheet metal of the inner fenders a lot, when you have the front crossmember out you will anyway clean and repaint them .. :)
Regards

Thomas

Yes, I may well end up doing similar.

David

In the end, I did grind off those bolts holding the fender wall to the crossbeam.

The front crossbeam is now completely detached from the chassis and body of the car but is still not removed.

The pic below shows the problem: I can't get the u-joint off the splined end of the steering column. It has to come out as the u-joint is inside the crossbeam and the hole the steering column passes through is too small for the U-joint to go through to take it out of there. I have removed the clamping bolts on both ends of the u-joint and the steering box end slides freely. The steering column end will not shift. Applying leverage just pulls the whole steering column down towards the steering box by about 1/2". I have applied PB Blaster penetrant, I have applied heat (albeit with only a small propane torch) and I have hammered a chisel in there (many, many times) but it won't separate from the column splines.

Any suggestions, please? I am considering just cutting the column to get it out but will have to check what would be entailed in repairing it and what parts may be needed and available.

David

Success!!!!!

I applied the propane torch for 30 minutes today. Then after some levering with a pickle fork, the spines came clear of the u-joint. Thanks for all the advice that got me to this point.

Here's the suspension subframe/crossbeam out of the car!!!!! Once I have dismantled the steering and upper wishbones, it will go to the welder for repair of the rusted out areas.

David

Well done David!
That was quite a job! Must be very satisfying to get the subframe off. In some ways it's fortunate that you are restoring everything because it means get the angle grinder out if need be.

Looking forward to seeing how you tackle the Wishbone Challenge :-)

When you get the wishbones off, in the past I wrote a post about getting to bushes out.

Probably don't need to tell you this, but make sure you clearly mark the wishbones arms so they can be re-assembled exactly where they were orignally.

Kevin

Thanks, Kevin. It's going to be a long process getting this repaired and reassembled....................................... ............

David

The subframe is back from the welder!!!!

The first pic shows the worst of the rusted area after the frame had been in an acid bath. The second shows the same area. The control arms are just being test-fitted.

The plan is eventually to paint this black but I am leaving for Nova Scotia very soon and won't be back until September. So, for now, I will temporarily bolt the subframe back in 'as is' to ensure the main chassis rails don't spread apart under the weight of the engine during the summer. The engine has been supported while the subframe has been out. So it should bolt straight back in but we'll see how it goes!!!!!

David