Silicone sealant and LHM

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Post Reply
User avatar
Dommo
Posts: 1191
Joined: 11 Apr 2009, 09:43
Location: Stoke-on-Trent
My Cars: Current
07 C5 VTX+ 2.2 HDi 173hp
97 S1 Activa
06 Boxster S
93 XM 2.1 Turbo SD

Previous cars
91 Toyota Soarer UZZ32 Active Suspension
97 S1 VSX 1.9 Turbo D
99 Xantia Activa
98 2.1TD Xantia
99 306
x 19

Silicone sealant and LHM

Post by Dommo »

Hi folks

Does LHM react with typical silicone sealant, bathroom sealant type stuff?

Cheers!
lexi
(Donor 2020)
Posts: 2803
Joined: 17 Apr 2008, 17:51
Location: Scotland
My Cars:
x 138

Post by lexi »

I wouldn`t think so. Only thing that eats silicone is the removers you get from Screwfix etc. It`s a very stable material that takes heat, oil the lot.
Citroen C5 1.6 HDI 110bhp Estate 06 plate

French Mistresses gone.
Citroen C5 HDI Mk 1 hatchback
Vel Satis 3.5 v6
ZX 1.9D Est.
ZX 1.9DHatch
Xantia 1.9td est.
Xantia 2.0 hdi Est.
Xantia V6 MK1
Xantia V6 MK 2
HDI
Posts: 1468
Joined: 22 Sep 2009, 15:46
Location: West Mids
My Cars:
x 7

Post by HDI »

Not quite !
Silicone generally does not resist long term exposure to mineral oil. However , there are special grades that are intended for use with oil , these will be the types that are used for gasket making , engine sealants etc.
Unless the type of bathroom sealer you are using specifically states that it will resist oil , it won't !
Now using '00 Xantia LX HDI, pov spec :(
My past Citroens :-
'00 Xantia SX HDI, now dead due to accident :(
'99 Xantia HDI 110 Exclusive, RIP :(
'97 Xantia TD SX
'96 Xantia TD LX
'96 ZX TD
'89 BX TD
'88 AX GT
'79 CX2400 Pallas (scrapped :( )
& a couple of Peugeots !
lexi
(Donor 2020)
Posts: 2803
Joined: 17 Apr 2008, 17:51
Location: Scotland
My Cars:
x 138

Post by lexi »

Basically there are only two real types of Silicone in this world. High modulous and low modulous. They have two different BS numbers and are put into a thousand different named tubes. Proper high mod silicone for bathrooms is basically the same type of rubber with a Fungicide to kill mould and not yellow.

Make sure you don`t use general "bathroom sealer" make sure it is silicone and not cheap acrylic water base

I have used ordinary silicone for rocker cover gaskets and many other engine uses etc for years.........no probs. Not saying that a special product wont work under more extreme circumstances...........it might and then again it could just be "snake oil" in some circumstances with a price tag to boot.

Try boiling some silicone in Lhm for a " Look Around You " type project :lol: :lol: :lol:
Citroen C5 1.6 HDI 110bhp Estate 06 plate

French Mistresses gone.
Citroen C5 HDI Mk 1 hatchback
Vel Satis 3.5 v6
ZX 1.9D Est.
ZX 1.9DHatch
Xantia 1.9td est.
Xantia 2.0 hdi Est.
Xantia V6 MK1
Xantia V6 MK 2
User avatar
Dommo
Posts: 1191
Joined: 11 Apr 2009, 09:43
Location: Stoke-on-Trent
My Cars: Current
07 C5 VTX+ 2.2 HDi 173hp
97 S1 Activa
06 Boxster S
93 XM 2.1 Turbo SD

Previous cars
91 Toyota Soarer UZZ32 Active Suspension
97 S1 VSX 1.9 Turbo D
99 Xantia Activa
98 2.1TD Xantia
99 306
x 19

Post by Dommo »

Cheers folks.

I think I have some yellow instant gasket now you mention it. Is the yellow-ness of it a key part to its composition??

Thanks.
addo
Sara Watson's Stalker
Posts: 7098
Joined: 19 Aug 2008, 12:38
Location: NEW South Wales, Australia. I'll show you "Far, far away" ;-)
My Cars: Peugeot 605
Citroën Berlingo
Alfa 147
x 93

Post by addo »

It's not just a contact cement based gasket maker? Does it have a strong acetone smell?
User avatar
Dommo
Posts: 1191
Joined: 11 Apr 2009, 09:43
Location: Stoke-on-Trent
My Cars: Current
07 C5 VTX+ 2.2 HDi 173hp
97 S1 Activa
06 Boxster S
93 XM 2.1 Turbo SD

Previous cars
91 Toyota Soarer UZZ32 Active Suspension
97 S1 VSX 1.9 Turbo D
99 Xantia Activa
98 2.1TD Xantia
99 306
x 19

Post by Dommo »

I'll be honest with you I've not got a clue, and I'm not sure of its smell, it's been sat in a tube in my garage for a long while, my brother bought and used some of it years ago.

If I've not got any in the garage would I basically be looking for some silicone instant gasket type stuff that says resistant to oil? I used some blue stuff on a sump recently, would that be LHM resistant?

Cheers.
addo
Sara Watson's Stalker
Posts: 7098
Joined: 19 Aug 2008, 12:38
Location: NEW South Wales, Australia. I'll show you "Far, far away" ;-)
My Cars: Peugeot 605
Citroën Berlingo
Alfa 147
x 93

Post by addo »

If you look at what's happening with silicone "gaskets" the oil/silicone interface is tiny compared to the depth of the seal.

I take it you're wanting to repair a rubber boot or something like that? It may be that a quality superglue could work, if the area glued isn't subject to massive flexing.
User avatar
Paul-R
Donor 2023
Posts: 6916
Joined: 07 May 2009, 16:24
Location: Wirral, NW England; Vaucluse 84, France
Lexia Available: Yes
My Cars: 2015 1.6 Blue HDi 120 Peugeot 308 Active SW
2013 2.0 HDi 163 C5 Exclusive Tourer
2003 2.0 HDi 110 C5 Exclusive Estate (Gone)
2001 2.0 HDi 90 Xsara Estate (Gone)
x 1369

Post by Paul-R »

Ordinary household silicone sealants (including the fungicidal type) react with water vapour and give off acetic acid. This is the vinegar smell that you get.

The proper gasket type silone sealant does NOT give off acetic acid. This is because it's generally not a good idea to mix acids with metal. Especially if it's held in close contact by the silicone itself.

I was under the impression that modulus was to do with the "slumpability" of a product, i.e. it's ability not to fall off when applied in largish amounts. A low modulus sealant will fill small cracks and gaps but a high modulus sealant wil bridge a large gap.
As I get older I think a lot about the hereafter - I go into a room and then wonder what I'm here after.

Inside every old person is a young person wondering what the hell happened.

"Trying is the first step towards failure" ~ Homer J Simpson​
lexi
(Donor 2020)
Posts: 2803
Joined: 17 Apr 2008, 17:51
Location: Scotland
My Cars:
x 138

Post by lexi »

Love that sig Paul :lol:

The acetic acid is normally present in the high modulous type. These are harder when cured, set faster and have slightly less "give". Where you shouldn't use this stuff is around joints that will have lots of thermal movement. ie. plastic window frames. THAT is a job for Low Modulous. This is now the different BS number and the proper ones have no acetic acid smell and cure to a joint which is more flexible........these types can be used in structural building joints up to 20mm wide.

Other no no`s for the high mod acetic acid stuff? Don`t use it on the back of a mirror to glue to a wall........the acid can eat through and damage mirror.
Don`t use when making a fish tank as it can kill fish if not cured properly.

These are jobs for Low mod. Adam makes a good point about actual contact area in joints.....miniscual. Also when bolted down the movement issue is nothing. My guess is that small tubes of silicone gasket stuff like RTV etc are probably low or high mod without the acetic acid production. I use Sikaflex on lots of stuff around a car also.That is a Polyurethane of high quality and differing grades of modulous (stiffness) that are recognisable by the number type on tube.
Citroen C5 1.6 HDI 110bhp Estate 06 plate

French Mistresses gone.
Citroen C5 HDI Mk 1 hatchback
Vel Satis 3.5 v6
ZX 1.9D Est.
ZX 1.9DHatch
Xantia 1.9td est.
Xantia 2.0 hdi Est.
Xantia V6 MK1
Xantia V6 MK 2
HDI
Posts: 1468
Joined: 22 Sep 2009, 15:46
Location: West Mids
My Cars:
x 7

Post by HDI »

Silicone sealants intended for oil applications are a different formulation , similar to fluro silicones which have total resistance to oil and fuel. Although the area exposed to oil in the assembled joint is minimal , the problem is that any excess extruded from the joint will be more likely to break away and cause a problem if it's a non oil resisting type.
Now using '00 Xantia LX HDI, pov spec :(
My past Citroens :-
'00 Xantia SX HDI, now dead due to accident :(
'99 Xantia HDI 110 Exclusive, RIP :(
'97 Xantia TD SX
'96 Xantia TD LX
'96 ZX TD
'89 BX TD
'88 AX GT
'79 CX2400 Pallas (scrapped :( )
& a couple of Peugeots !
lexi
(Donor 2020)
Posts: 2803
Joined: 17 Apr 2008, 17:51
Location: Scotland
My Cars:
x 138

Post by lexi »

Whenever the word Fluro comes up I smile. Many tests have been done on "flurocarbon" fishing line and basically they are a rip off in price and what they are supposed to be in the actual term fluro. Some tests said it was line with soap on it. :lol:
Afaik there are no fluro silicones in a tube. I think they are manufacturer extruded into shape?



Rubbers are interesting :shock: :lol:
Citroen C5 1.6 HDI 110bhp Estate 06 plate

French Mistresses gone.
Citroen C5 HDI Mk 1 hatchback
Vel Satis 3.5 v6
ZX 1.9D Est.
ZX 1.9DHatch
Xantia 1.9td est.
Xantia 2.0 hdi Est.
Xantia V6 MK1
Xantia V6 MK 2
User avatar
Dommo
Posts: 1191
Joined: 11 Apr 2009, 09:43
Location: Stoke-on-Trent
My Cars: Current
07 C5 VTX+ 2.2 HDi 173hp
97 S1 Activa
06 Boxster S
93 XM 2.1 Turbo SD

Previous cars
91 Toyota Soarer UZZ32 Active Suspension
97 S1 VSX 1.9 Turbo D
99 Xantia Activa
98 2.1TD Xantia
99 306
x 19

Post by Dommo »

Basically the rear ram on my Activa is weeping slightly, one drip every few minutes or so when running. But probably enough for mr MOT man to fail it I would imagine. Basically I want to get it through it's MOT then save up for a new rear ram in the near future, at the moment it seems stupid to buy a ram for such a tiny amount of leakage.

I think that providing a better seal around the bottom of the ram gaiter would stop it leaking, possibly only in the short term, but possibly long term too.

I'll have to admit, I'm very confused about the info in this thread! For the bottom of the ram gaiter are we suggesting that I'm best off with low modulus?

I have some stuff that apparantly doesn't 'set', but says it's suitable for water pumps, oil sump pans, rocker covers, etc. Does that suggest it's LHM suitable??

I've also got some blue stuff that I used specifically on a sump pan and it did have the vinegar smell, and it set into a hard rubbery consistancy.

Has anyone used any specific products with LHM? If so what is the suggested one to use?

Thanks and sorry for asking the same questions over and over :oops: :lol:

Dom.
lexi
(Donor 2020)
Posts: 2803
Joined: 17 Apr 2008, 17:51
Location: Scotland
My Cars:
x 138

Post by lexi »

Sorry for confusion mate We were chewing the fat a bit there. If you are in doubt about all this why not go and buy a dedicated Silicone job like this?
http://www.halfords.com/webapp/wcs/stor ... yId_165691

Whadya think?

Always keep asking on the forum till you get the answer.....or until you are sure nobody knows :lol:
Citroen C5 1.6 HDI 110bhp Estate 06 plate

French Mistresses gone.
Citroen C5 HDI Mk 1 hatchback
Vel Satis 3.5 v6
ZX 1.9D Est.
ZX 1.9DHatch
Xantia 1.9td est.
Xantia 2.0 hdi Est.
Xantia V6 MK1
Xantia V6 MK 2
User avatar
Dommo
Posts: 1191
Joined: 11 Apr 2009, 09:43
Location: Stoke-on-Trent
My Cars: Current
07 C5 VTX+ 2.2 HDi 173hp
97 S1 Activa
06 Boxster S
93 XM 2.1 Turbo SD

Previous cars
91 Toyota Soarer UZZ32 Active Suspension
97 S1 VSX 1.9 Turbo D
99 Xantia Activa
98 2.1TD Xantia
99 306
x 19

Post by Dommo »

Cheers lexi. Im fairly sure I saw that in halfords today but picked another one as it sounded better (the loctite box had less info on than on their website) but now I'm not so sure...

I'll have a shufty when I get home! Cheers.
Post Reply