How do I replace the rear subframe mounts?

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Jim Martin
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How do I replace the rear subframe mounts?

Post by Jim Martin » Wed Apr 19, 2017 1:52 pm

I'm working through a fairly short list of bits and pieces that need sorting on my recently acquired TF 135.

The only job that is scaring me is replacing the front mounts on the rear subframe. One is very corroded, and half is missing, so it's fairly urgent.

I couldn't find a How To section on here, or a step-by-step guide anywhere on the internet with (clear) pics specifically for these mounts.

I have access to a garage with an inspection pit, but having read that the smaller bolts tend to shear off and that the subframe needs to be dropped to access the large ones, maybe I should leave this to a pro and just pay them to do the hard work.

How much would this cost?

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Re: How do I replace the rear subframe mounts?

Post by The old one » Wed Apr 19, 2017 3:58 pm

Hi Jim,
The problem with the front mounts is not so much dropping the subframe but being able to soak them in releasing fluid. As the nuts are captive it's ni impossible to get to them, if the heads shear off then it's drill out time and a M8 tap.
Steve

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Re: How do I replace the rear subframe mounts?

Post by Jim Martin » Wed Apr 19, 2017 8:49 pm

Thanks Steve.

Indeed. I have a can of Plusgas, but what is the best way to use it when the bolts are essentially upside down? Cling film? Even then, it can't really defy gravity it's questionable whether to waste a can on it!

Aside from that, do the rear mounts also have to be undone in order to drop the subframe, or will it give enough clearance just by removing those four bolts at the front?

I've read that you can replace the mounts without dropping the frame if you grind off the old ones and the bolt that goes through it. Any truth to that?

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Re: How do I replace the rear subframe mounts?

Post by talkingcars » Wed Apr 19, 2017 11:01 pm

I am currently doing similar, I had two difficult bolts so every night for a week I put a few drops of plus gas at the point where the vertical bolts meet the mount and where the mount touched the chassis. After a week both came undone at the first attempt.

The horizontal bolts are hard work, even my Ryobi impact wrench didn't manage 2 of them so I ended up grinding away one face of the bolt until I was getting blue heat marks as I got close to the thread, then the Ryobi worked.

You may find some how to info here.
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Re: How do I replace the rear subframe mounts?

Post by The old one » Thu Apr 20, 2017 8:52 am

It looks like Talking cars had a bit more luck then I did, I managed to release 3 of the 4, so had to drill one. I will have to exercise a little more patients. (more hast less speed)

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Re: How do I replace the rear subframe mounts?

Post by Jim Martin » Thu Apr 20, 2017 12:23 pm

That's good to hear that Plusgas can - and does - work. :)

I have a Ryobi impact wrench as well, and it has been relatively useful. But I tried it on the caliper carrier bolts at the front, and it wouldn't loosen them at all. Maybe I should persevere with the Plusgas!

Just to clarify, do the rear mounts also have to be undone to drop the subframe in order to access those big horizontal bolts at the front?

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Re: How do I replace the rear subframe mounts?

Post by The old one » Thu Apr 20, 2017 5:52 pm

Try dropping the front very slowly and see if you have enough clearance manifold to bulkhead. Also bear in mind you have clutch pipework hoses etc close to the front of the frame. When I removed mine i took the whole subframe out in one go, but you should have enough clearance, just take your time. I used one of these quad bike lifts they have a working limit of 1500kg which is more than the car. http://www.ebay.co.uk/itm/380922360214 there people on here with a lot more MGF/TF experience than me, I'm still learning hope it works out ok.
Steve

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Re: How do I replace the rear subframe mounts?

Post by Jim Martin » Fri Apr 21, 2017 11:48 am

Thanks Steve. It's surprising how cheap those lifts can be.

Fortunately, I have access to a friend's garage with a two-post lift and - presumably - a transmission jack. The main limitation is that I can't just leave the car there as it has to be done out of working hours! We'll see how it goes - angle grinder may come in handy.

I'll keep you posted, but may not attempt this for a few weeks yet. First need to source replacement stainless bolts for both mounts, so if anyone has a link where I can get them...

Jim

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Re: How do I replace the rear subframe mounts?

Post by Rob Bell » Fri Apr 21, 2017 1:29 pm

Try tightening the chassis screws before attempting to undo them - it helps un-crack any "sticktion" - but dowsing in penetrating oil (Plusgas is my favourite too) is a very good plan. There are exposed threads within the hidden box sections - so getting plenty of penetrating oil in here is probably a good idea too...

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Re: How do I replace the rear subframe mounts?

Post by Tipper » Sat Apr 22, 2017 10:49 am

The old one wrote:Try dropping the front very slowly and see if you have enough clearance manifold to bulkhead. Also bear in mind you have clutch pipework hoses etc close to the front of the frame. When I removed mine i took the whole subframe out in one go, but you should have enough clearance, just take your time. I used one of these quad bike lifts they have a working limit of 1500kg which is more than the car. http://www.ebay.co.uk/itm/380922360214 there people on here with a lot more MGF/TF experience than me, I'm still learning hope it works out ok.
Steve
Can I just point out that the lift identified has a safe working load limit of only 1500 lbs and NOT 1500kg!!!

1500lbs is only 680kg. An MGF/TF is about 1100kg and it's heavier at the back than the front. It may be OK for a one end only lift but for me that would be too close for comfort for the back end and could present a real risk of failure and you may be somewhere under the car when it fails!

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Re: How do I replace the rear subframe mounts?

Post by The old one » Sat Apr 22, 2017 4:28 pm

Just checked 1500lbs not 1500kg should have gone to Specsavers

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Re: How do I replace the rear subframe mounts?

Post by john_g » Wed Apr 26, 2017 9:43 pm

Jim my fronts are looking suspect too.. I take note of the difficulty with the plusgas application

the rears.. I did one last month and the other last year, they seemed straightforward.. I could remove the smaller bolts ok (with care and prayer) and the large bolt was removable without much fuss.. (I had a trolley jack under and (think) maybe let the sub down slightly at that corner) either way it was pretty easy..

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Re: How do I replace the rear subframe mounts?

Post by Jim Martin » Thu Apr 27, 2017 3:16 pm

Thanks guys :)

@Rob - you mention exposed threads in the hidden box sections. How, then could one get the penetrating oil in there? That's a great tip on tightening before undoing. I'll try that!

Also, John, that's good to hear the rears aren't too difficult, and the big bolts aren't a pain. Having just had to cut four massive bolts (eight cuts) out of the trailing arms of my Focus because they were seized, I imagined a similar situation with subframe bolts.

If anything, as the TF is a late 2004 model, it might - just might - be a little less hassle than an MGF 10 years older. Though, I've heard the MGF doesn't have the same solid mounts.

I'll get under it at the weekend, spray (and pray) with the Plusgas and gingerly try to get some of the chassis bolts loosened.

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Re: How do I replace the rear subframe mounts?

Post by john_g » Thu Apr 27, 2017 5:25 pm

the big bolts, I used a socket and (I think a short extension) and a 1/2 " bar to be able to hold them while undoing the easy to get to nyloc nuts.
or possibly I used a deep socket only.. either way you need a few cm but not too much.. you will see what i mean :)

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Re: How do I replace the rear subframe mounts?

Post by talkingcars » Thu Apr 27, 2017 10:16 pm

Jim

I put a few drops on the visible joints on the mount to body bolts several times over the week before trying to undo them.

I had to cut and or grind some of the large nuts to get them undone, even with a impact wrench.

Even a 2004 car is 13 years old, don't expect it to be easy.

The MGF mounts are essentially the same as the TF except they have a rubber bush in the middle.

James
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Re: How do I replace the rear subframe mounts?

Post by Jim Martin » Fri Apr 28, 2017 10:23 am

Sounds a lot like a lottery then :)

They might be easy; they might be a right PITA and require the attention of Mr Grinder.

We shall see.

Here's hoping for some better weather. There was frost on the cars yesterday morning!

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Re: How do I replace the rear subframe mounts?

Post by Rob Bell » Fri Apr 28, 2017 12:38 pm

MGF mounts tend to last longer because the rubber fills the void that on the TF remains exposed and fills with water and mud to rot it out... :(

Getting into the enclosed box section is no easy task. Next time I drop the subframe, I'll drill some exploratory holes - and may be tap for a grease nipple... ;)

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Re: How do I replace the rear subframe mounts?

Post by Jim Martin » Fri Apr 28, 2017 1:18 pm

Ah, so I can't really do anything about it. It sounds like a catch 22, as you have to undo the bolts in order to drop the subframe so you can drill some holes for greasing / spraying the Plusgas.

Clearly the designers weren't bothered about making it possible to replace mounts and bushes without dropping subframes!

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Re: How do I replace the rear subframe mounts?

Post by Rob Bell » Fri Apr 28, 2017 1:45 pm

I dare say that it wasn't a prime design consideration, as replacement of the mounts would only be necessary well after the end of the specified design life of the vehicle, which I reckon is typically 10-15 years...

Actually, they might have designed the car so it lasts until the end of the warranty period! :lol:

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Re: How do I replace the rear subframe mounts?

Post by Tipper » Fri Apr 28, 2017 6:13 pm

Another reason these bolts rust then shear is that to speed assembly during production MGR used self-threading bolts forced into an 'unthreaded' hole. They are used all over these cars so be warned!

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