Urethane casting compound to make bushes

**SystemRat** · 04-02-08, 07:05 PM

I’ve just done a differential bush in my car and the replacement part
costs an arm and a leg here in Oz so I was happy to find an article on
how to cast your own.

Here is an example relevant to my car but you can do the same
thing with some captive engine mounts and lots of other parts if you
need to make some

This place sells 1.4 kg (about 1.4 litres) for $34.00 (Flexible hardness 85)
The stuff listed on the website is clear you don’t need or want that for
engine components as it takes longer to dry.

The stuff I have cures in 4 to 6 hours

Hope this helps someone.

It’s also kind of handy to know where to buy this stuff for other uses too.

**global88** · 04-02-08, 07:33 PM

Thanks Systemrat, very interesting and it may come in handy one day.

Im a little cautious of urethane suspension bushes.
The softness variation from one type to another can really change the handeling characteristics.

Some very hard (normaly yellow) bushes can cause suspension failure due not having enough shock absorbtion.

Did you note the urethane bush in the link you provided had unstuck itself from the metal frame after a couple of years. On a more vital component this would lead to catestrophic failure, not something you want on the street.

Great idea, use with caution.

I think with a little play you could come up with a reliable compound mix and better prep and adhesion to the metal frame.

But would you risk your life testing it?

**tagg** · 04-02-08, 07:42 PM

Thats sweet SystemRat.

Tagg

**SystemRat** · 04-02-08, 07:53 PM

I would not use this on a safety critical part but in this case and that of an engine mount on this car there is little risk.

The part I am repairing is cosmetic in that it stops vibration and noise from the diff assembly.

When that bush fails the diff is still captive in its mounts it just thumps about.

I’ve replace engine mounts on this car to and used genuine parts for that although some people in the states have also used urethane there too.

These mounts are captive meaning if you stripped out the rubber the mount would still be secure.

I am hoping my choice of compound and surface preparation might make this a good repair and perhaps stronger than the original part which tends to fail.

Unfortunately there is no OEM replacement part available for this in Oz and Burson auto told me they send off the bush assembly to be refurbished meaning exactly what I am about to do to fix it.

**global88** · 04-02-08, 08:20 PM

An engine mount could become a critical link.

I use to break passenger side mounts on ford v8s from drag type starts, and when yourve got tunnelrams sticking out of the bonnet you can see how the engine jumps, its pretty scary.

I overcame breaking one every 3 months by building a tourque rod from the block to the chassis to stop the block twisting under tourque.

In the right circumstances a fuel line may rupture when the mount breaks, you can work out the rest.

Keep in mind in the link you gave, the ureathane seperated from the metal.

Still i have to agree its a great idea, just use with caution.

One other thing is some later model cars have engine mounts that interlock. The plate that faces the block and the plate that faces the chassis, interlock with a one cm space. If there is more than a cm of pull in the mount, the brackets lock, metal to metal.
In this case id use it without doubt.

**weirdo** · 04-02-08, 10:17 PM

Thanks mate, that's some great info.
I was chasing some engine mounts and gearbox mounts for a Daihatsu Delta last year and couldn't find any. (apart from some ripoff overpriced ones)
This shit would have been the ducks nuts.

**tytower** · 04-03-08, 09:59 PM

I appreciate this link too --thanks

Another useful quick fix is Sikaflex in a tube -works the same and stays workable for a long time --sets bloody strong and flexible try some just make a form ,say a washer shape and squeeze it in and let it harden.

Watch out the Missus don't get any ideas though!