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