Technical manifold Gasket

[magicmonkey]

Hi Guys
I've got a 999cc FIRE engine Uno which is a nice little runner, the only problem in the manifold gasket, I've replaced it twice now and every time I replace it the gasket goes and it starts making a horrible noise again, I'm using Holts FireGum as a gasket sealant and going the bolts up tight enough but it just won't stay right. Could anyone tell me what I'm doing wrong or if it is just the gaskets being of poor quality, where could I get some propper ones?

 

[Dutchie]

think you are talking abouth the outlet side gasket..??
if so you never use firegum or something like that when assembling the gasket back on. !!
just clean of both surfaces (head and manifold) and the gasket should do the sealing trick.
if it's still blowing everytime like you said, it could be becuase of the gum gum fire thing you use, or the manifold not being completly flat anymore.
only thing then to do is to replace it with another one.
This all goes for the outlet side manifold.

the inlet side is kinda the same, but that can be made "flat" again with proper machines.
For the inlet side never use any liquid "extra" sealent, just the gasket to seal it of.!
Sorry my enlgish kinda let's me down here but I think you get my point.

 

[magicmonkey]

it's sometimes refered to as the downshaft gasket I'm told, basicaly where the exhaust leaves the engine block then joins the exhaust pipe just between the engine block and the radiator/fan...

I'll try buying another gasket and doing it without the sealant! The gasket might be sub standard though to be honest, it looks like 2 sheets of very thin metal with some cardboard inbetween...

 

[Dunc Uno Turbo]

could be ur engine mounts are knackered. causing excesive movement in ur engine which causes ur manifold to blow

Dunc

 

[magicmonkey]

hmm, I hope it's not the engine mounts! The gasket always goes in the same place, passenger side towards tofront of the car though so I suppose it could be something like that. There's not a spot of rust on the car anywhere though so it probably won't be rusted engine mounts. Could it just be that I need to get in there and tighen them up?

 

[jjhepburn]

It could be the rubber engine mounts (easy to replace) to test them just grab hold of the arm that goes to each of the three mounts and shake it, if it moves heaps then the mount is stuffed (it should move a little).

But make sure when you change the gasket that you give the mating surfaces a good clean, I use 120 grit sandpaper on a sanding block to ensure its flat and all traces of old gasket are gone.

If you have a new gasket (something I've never had the luxury of before) you shouldn’t need any sealant.

 

[magicmonkey]

Right, I'll be ordering a new gasket this afternoon and I'll let you guys know how it goes...

 

[Dutchie]

oohh you mean that gasket.

indeed no need for any extra seelant, it will only make it blow out faster.
give it a good cleaning/sanding job before refitting the new gasket.
and indeed the reason it blows out could also be the engine mountings, shaing the eninge with your hands should only give a little movement.
you could get an extra hand, let them put the car in 3th or 4th gear (wth engine running) and the handbrake fully on.
Now let them lift off the clutch a bit, so the car starts shaking, the engine should only move like a inch (or 2) then.
if it moves move, then the engine mounts are not that good any more and may need replacing.

 

[M@nticore]

what i normally do, is clean both surfaces and then just put a light film of decent black silicone on either side of the gasket and refit it. remeber to get new studs and locknuts aswell.
i use silicone on all manifold and head gesket replacements, works like a charm.

 

[LuiPoland]

i changed this fu*** gasket in my uno just about 3 hours ago

so it's normal to uno

 

[Dutchie]

we used to own a ritmo, with the 75 bhp engine the 1.5 overheadcam one.
It is the same as in the uno (not the fire one's).
It had the nasty habbit aswel, it blew out that gasket like a zillion times in the short time we had that car.
But besides that is was a great motor, pulled a trailer back and fort for our holliday with me mom behind the wheel, doing 150 Km'h on the german freeway..
Got us a ticket way over the 300 Euro's..:bang:

 

[Chas Uno]

what i normally do, is clean both surfaces and then just put a light film of decent black silicone on either side of the gasket and refit it. remeber to get new studs and locknuts aswell.
i use silicone on all manifold and head gesket replacements, works like a charm.

Use use silicone on exhaust and head gaskets

Most head gaskets should be changed without any gasket sealant - that's what all the manufacturers instructions recommend and how they are designed to work.

And surely using silicone sealant on an exhaust manifold gasket simply wouldn't work? The heat from the exhaust would burn it away!

I've always replaced headgaskets 'dry', without any sealant at all, with no problems. And for the exhaust manifold, as long as the mating surfaces between it and the head are clean and flat, the compressable metal gaskets work fine without any sealant. For the exhaust manifold to downpipe gasket, if the copper gasket doesn't seal properly only then would I add a bit of 'exhaust assembly paste'. This is designed to expand slightly when heated for the first time and fills in any imperfections in the mating surfaces giving a gas tight seal.

Then again, some newer designs might need some form of sealant, but not the venerable FIRE engine to my knowledge!

 

[M@nticore]

i've been working on mercedes benz now for 3 years, on the CDI diesel mercs, you don't use an exhaust flange gasket to seal it, you only use black silicone sealant, so if it works on a merc it would sure as hell work on a cheap fiat engine.

 

[Chas Uno]

I'm going by 20 years worth of mechanic experience M@nticore, and having worked on many different vehicles/ engines over those years.

It is possible that newer engine designs use different methods for sealing, but most of the vehicles I work on are of an older design. The original FIRE engine was first unleashed 21 years ago so some modern techniques don't apply!

I always follow manufacturers instructions, and also the instructions given by the gasket manufacturers. None of the head gaskets I have changed have ever required sealant or gasket cement, and all the instructions strongly warned against using them. Same applies with exhaust manifold gaskets, with the one exception being to use exhaust assembly paste as a last resort if the flange has been eroded/ damaged. This paste expands when heated and sets hard to seal an imperfect joint, unlike silicone which sets soft and doesn't have the same ability to withstand the high temperatures of the exhaust.

Inlet manifolds CAN use silicone type sealant, though normally it is Blue Hylomar or RTV sealant (Room Temperature Vulcanising). The inlet manifold doesn't reach anywhere near the same temperatures as an exhaust manifold so can use these types of sealant.

It's not a good idea to compare a modern Mercedes Diesel engine to an older Fiat petrol engine. Designs change, and what applies to one design might not apply to another. Also, diesels tend to run cooler than petrol engines (they don't ignite the fuel with a spark as they use compression instead - diesels don't use spark plugs except for glow plugs to aid starting!), so I'd suspect that their exhaust manifolds run cooler. That might be why Mercedes diesels can use sealant on diesel exhaust manifolds whereas older petrol engines must use proper exhaust gaskets.

If there is some new sealant that can be used as in the diesel Mercedes, can you tell the forum what exactly it is? What make? What are the specifications/ working temperature range? It would help a lot of people if we could get hold of some of this sealant!

 

[Louie Bee]

Working as a parts book author for a large UK diesel manufacturer I have only seen 2 part numbers for joint sealant. If I remember correctly, they were only used on sumps for a short time many years ago. I was told the compound sealed too well. When it came to removing the sump, it was too hard to split the join, and further damage was often caused. They resorted back to dry gaskets and seals.

With todays ever tightening pollution requirements placed upon engine manufacturers, gasket material is coming on leaps and bounds . I haven’t written any parts books that include a sealing compound. That doesn’t rule out the use by competitors .

…Same applies with exhaust manifold gaskets, with the one exception being to use exhaust assembly paste as a last resort if the flange has been eroded/ damaged. This paste expands when heated and sets hard to seal an imperfect joint...

Funny you mention exhaust paste . (Everyone) remember to use sparingly, or it can squeeze into the exhaust channel and possibly restrict the gas flow :spin: .

Similarly for other sealants, use sparingly if you must use them. The last thing you want is excess sealing compound inside the engine .

M@nticore mate, how many head gaskets have you used a compound on? Was that after having the head skimmed?

Regards,

 

[SuperUno]

When i got a stainless steel exhaust section made for an early Uno, they used a form of silicon sealant to join the pipes up. It worked very well, this was very well sealed, in fact it was quite hard to separate.
It also sealed the exhuast gases very well.
This stuff was clear, and looked to me just liked normal bathroom sealant, but don't quote me on this.

On another note, have now decided to take the mighty SuperUno stage rallying, so i have bought yet mroe rallying stuff for the old girl

Cheers

Matt

 

[Morty Mort]

Hello.

If you buy gaskets from FIAT which you should, you will notice the inlet manifold gasket is rubber, and the TWO or FOUR exhaust gaskets are not. Are you using some cheap replacement gasket? Don't do that. Get gaskets from FIAT and replace. There is not ONE gasket in front, they are splitted, propably due to metal expanding etc.

Morten.