R8 Engine Mount Failure!
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Thread: R8 Engine Mount Failure!

  1. #1
    Fellow Frogger! R8 Dream's Avatar
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    Default R8 Engine Mount Failure!

    I had to pull the engine out on the weekend to investigate a problem with clutch slippage which occurs under hard acceleration. (Topic for another thread!!)

    Anyway, after disconnecting all ancillaries and leaving 4 positional bolts in place (2 at bellhousing and one either side of the engine mount) ensuring the car & engine where dead level, I carefully slid the engine back.

    Upon clearing the mounts, I noticed that the RH engine mount had delaminated!

    These were purchased from Mecaparts around 5 years ago but only running in my R8 for around 6 months.

    Done a few events (track day, hill climb and sprint) and around 800km road use only.

    Has anyone had a similar experience?

    Is the mount dead, or can I glue it back togetherness?

    i recall pulling out the 40+ year old ones and they were still intact!

    Is there some 'special' technique needed in installing or maintaining, or just poor quality?

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    Cheers
    Angelo

  2. #2
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    That’s disapointing Angelo, looks like poor manufacturing to me. Often suspected the new rubber components are not as good as the old original Renault stuff
    Brian

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    I recall Frans posted some pics recently sharing a very good engine mount he designed for his racing R8G that supersedes the old Renault mount that is prone to failure when the glue on the rubber bond lets go.

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    bad rubber mix and adhesion? or crap rubber? is there rubber still on the other surface where the main rubber delaminated? just thinking....
    ďListen very carefully, I shall say this only once.Ē Cheers. John

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    Quote Originally Posted by Shoji View Post
    bad rubber mix and adhesion? or crap rubber? is there rubber still on the other surface where the main rubber delaminated? just thinking....
    No rubber, clean break off the metal backing plate to rubber.

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    Quote Originally Posted by Bustamif View Post
    I recall Frans posted some pics recently sharing a very good engine mount he designed for his racing R8G that supersedes the old Renault mount that is prone to failure when the glue on the rubber bond lets go.
    I do recall, but had a quick search but could not find anything. Do you recall under what thread it was posted?

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    Fellow Frogger! R8philSA's Avatar
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    Hi Angelo.

    I just repaired my Gearbox mounts on 'BARNIE'

    Get some Loctite 495 specially made for bonding rubber to metal. I got mine of the internet about $12 bottle. Great for door rubbers as well. Just make sure the areas are perfectly clean before you add the glue. Works like Super Glue.

    Cheers mate
    Phil

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    1000+ Posts Frans's Avatar
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    Hi.I posted the details on C. Lees's resto thread.
    Frans.

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    As a temporary fix I have used the glue and I added a couple of screws into the rubber from the backing plate to take some of the sheer load. I have since replaced them with new but they were still working when removed.

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    Quote Originally Posted by Frans View Post
    Hi.I posted the details on C. Lees's resto thread.
    Frans.
    Thanks Frans, I will take a look at them and see what is involved in making them up.

    Angelo

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    Quote Originally Posted by R8philSA View Post
    Hi Angelo.

    I just repaired my Gearbox mounts on 'BARNIE'

    Get some Loctite 495 specially made for bonding rubber to metal. I got mine of the internet about $12 bottle. Great for door rubbers as well. Just make sure the areas are perfectly clean before you add the glue. Works like Super Glue.

    Cheers mate
    Phil
    Thanks Phil, I will look at all my options including this. Loctite make very good industry products so I am sure it will work.
    Funny but I must say I don't know how long it has been like this, but I did not notice any change, noise etc
    Angelo

  12. #12
    1000+ Posts Frans's Avatar
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    Quote Originally Posted by R8 Dream View Post
    Thanks Phil, I will look at all my options including this. Loctite make very good industry products so I am sure it will work.
    Funny but I must say I don't know how long it has been like this, but I did not notice any change, noise etc
    Angelo
    You wouldn't with a bit of noise from your modded engine and heavy RH foot. However, have a look at your photo again and see that it has come to rest in the safety base of the holder. The mounting has rubber cushions on the extreme outsides to prevent the engine from falling out when it breaks. Note my statement, "when" it breaks and not "if" it breaks. I think they used to be OK with the original 55 odd hp.

    Frans.
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  13. #13
    1000+ Posts Frans's Avatar
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    I see it in leverage action. The rear wheels are the pivot point, then you have 2m to the front and 1m to the back. The lever to lift the front of the car is at the engine mount, the pivot at the rear wheels, so the rear mounting will have to take double the strain of the frontal lifted weight.

    It is like the opposite of a tommy bar. If you pull at the long end the leverage is in your favour, unlike the poor engine mount.

    Frans.
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  14. #14
    1000+ Posts driven's Avatar
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    In my industry experience it is not possible to rebond a failed metal to rubber joint.
    It is complex process, Renault ones work, copies fail easily..

    Take your parts to an Engineering shop and they can make a new one for you. Google rubber bonding metal

    Read all about the complex process as good as many

    https://www.azom.com/article.aspx?ArticleID=917

    I feel using a couple of screws on an engine mount is bush mechanic/emergency get you home only

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    Quote Originally Posted by Frans View Post
    You wouldn't with a bit of noise from your modded engine and heavy RH foot. However, have a look at your photo again and see that it has come to rest in the safety base of the holder. The mounting has rubber cushions on the extreme outsides to prevent the engine from falling out when it breaks. Note my statement, "when" it breaks and not "if" it breaks. I think they used to be OK with the original 55 odd hp.

    Frans.
    Good pick up Frans re: resting on safety base - I did not pick that.

    I though R8G 1300 engines could top 100+ hp, so are these mounts different to the R8 mounts?

  16. #16
    1000+ Posts Frans's Avatar
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    Hi Angelo,

    Yes the R8G tops the 100hp by far. The fact that you could in the past get 100k miles on a set of mountings is with the 55hp engines and I should add, the factory quality rubber. The more hp the less the mounting life and in plenty cases I saw the mountings rest in that base pocket but they didn't tear like yours. They sagged until they were lying in those pockets. Once they reached that shape/position they will last forever because the strain isn't on the rubber block anymore and because of the cushions you don't really notice it as in your own experience.

    I have already spoken my mind about the R8/R10 mountings elsewhere. That includes the GB mountings. Thankfully I have not one original mounting on the race car. I cannot recall that I have ever noticed or experienced Cortinas or Anglias of the same time having mounting breakages because they all rest on the mounting, not hanging off the side of it trying to tear it off.

    Frans
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    Thanks for the good warnings on those rear engine mounts Frans.

    I'm wondering while the engine is still out if I should install an extra hard rubber block under each rubber mount to assist with the shearing effect. Any thoughts on this would be appreciated.
    Cheers
    Phil

  18. #18
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    Quote Originally Posted by R8philSA View Post
    Thanks for the good warnings on those rear engine mounts Frans.

    I'm wondering while the engine is still out if I should install an extra hard rubber block under each rubber mount to assist with the shearing effect. Any thoughts on this would be appreciated.
    Cheers
    Phil
    Have a look at what Frans has done. That would be my advice. His gets a better work out than most, if not all R8s in our part of the world!
    JohnW

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  19. #19
    1000+ Posts Frans's Avatar
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    Hi Phil,

    It is up to you really. If I were you I would make them myself.

    The mountings I've used are cheap and nasty from a rubber dealer here in NZ. They sell all rubber and foam products, Google Para Rubber. They are also used in industry to mount electrical motors for damping and sound insulation. Then all you need is some angle iron and a hacksaw. The mounting in the photos are my Mk1 model made from 6mm Aluminium angle. They weren't strong enough and were pulled apart at the 90 degree corner. Mk 2 is made from 5mm mild steel angle iron. I did not have an uneven length angle so I just welded a piece on where the longer part is needed. (I made a V-joint and welded it and then grind it flat for a nice surface)





    This is the LH mounting Mk1 that didn't last. It gives you an idea of the force on these mountings as the alloy ones were literary pulled apart (sheared) at he corner of the long angle and that happened after the second event. Mk2 looks the same but mild steel.

    I am sure that if you don't do it now, you will be doing it soon after your first event because the TS engine is slightly heavier and has a lot more torque with the bigger flywheel as well. Remember that if the mounting has sheared of, the engine will be lifted to the top of the mounting housing when you lift up on the throttle and even worse when you start gearing back for a corner.

    Another thing to remember and this was discussed elsewhere on AF with the guy from GordiniWorkshop in Scotland where it was said that with negative camber on the rear, you can change the rear wheel alignment by increasing or decreasing the rear of the engine and that it has an effect on handling. Lowering will give toe out and higher will give toe in. So what ever you have the height at you would ideally keep it steady on that height.

    Regards, Frans.
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  20. #20
    Fellow Frogger! R8 Dream's Avatar
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    I think I can give a sensible explanation as to what has happened to the engine mount (after receiving words of wisdom from my good friend Rob S).

    I am running a R8 (R16TS) Strong Box which utilizes a spacer ring of 11mm.

    The gearbox mount was slotted to take the offset, but i appear to have overlooked the need to slot the LH side of the engine mount brace (by 5.5mm) and pack out the RH side by also 5.5mm.

    I think this has had the effect of inducing twist forcing the RH hound to delaminate, which the LH was left unscathed (under compression - so ok for the time being).

    This of course makes sense to me and I will go about remedying this issue this weekend, without the need of (I think) of using the special mounts developed by Frans.
    I am of course happy to take comments, suggestions and criticisms.

    Angelo

  21. #21
    Too many posts! JohnW's Avatar
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    Ah. Geckoeng has discussed with me in the past the wisdom of offsetting the entire power unit by half the diff. ring thickness. You'd certainly have stressed one side, tensionally, rather more than the other. That does make sense of the failure, if it were the more tensioned side of course.

    I'm looking forward to the Loctite report but do like Frans' approach!

    Struggling with a bit of Citroen CX radiator hose geometry this week, after a new AC condenser and a non-standard alternator, I'm all too well aware that modifying anything cab lead you down unexpected paths with trip-up points galore!!

    Cheers
    JohnW

    Renault 4CV 1951
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    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
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    Hi Frans. Thanks for the good advice and I understand exactly what you are saying.
    I might sit with what I have in there at the moment but I will compliment the original rubbers with an extra harder rubber block, especially on the torque side of twisting moments of force.
    My plan for this car is mainly sprints, hill climbs will be secondary.
    Thanks again to all who have made comments here, it really helps when your up to your neck in restoration.
    Cheers
    Phil
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