Exhaust Manifold Gaskets

[Guest JRMobile]

When doing an engine bay inspection yesterday I discovered a blown exhaust gasket (again) and swore quietly to myself - the weather today being blue skies, light wind - great for flying!!

 

Question for anyone with an early 3300 with the flat manifold attachment, is there an off-the-shelf gasket available or is it a genuine jabiru part.

 

Any tricks of the trade when refitting the manifold to overcome this issue?

 

Any input greatly appreciated :thumb_up: John

 

 

[Yenn]

You can buy manifold gasket material from people like Repco. It is a lead grey sheet about 1mm or more thick. Hard to cut cleanly, but a wad punch works OK.

 

 

[Guest JRMobile]

Thanks yenn, I"ll check it out

 

I had a thought in the back of head that sinced jab sourced a lot of thier parts from the auto industry they might be off the shelf.

 

Cheers

 

JR

 

 

[facthunter]

Exhaust gasket.

 

JR, The shape of the manifold/head joint would be unique to Jabiru, and there would be no auto equivalent. Check the flatness of the flange surface. Most aircraft Ex. flanges are pretty thin (to save weight) and can end up hollow in the middle and will then not seal properly. Nev..

 

 

[Guest brentc]

If you are interested there is a guy in SA that will modify your old heads to not require gaskets. Another forum member here has had this mod done with what I believe was complete success? If you are interested let me know and I'll put you in touch. The modification is done live on the aircraft (no need to remove the engine).

 

 

[Guest JRMobile]

"Check the flatness of the flange surface" There you go! always another way to look at a problem, cheers Nev,

 

Brentc, could you PM me the details of "a guy in SA that will modify your old head" It sounds painful, but I would be interested to find out more.

 

 

[Guest brentc]

From what I've heard it's quite easy and is done with a jig attached to the head and it's done in one fluid motion.

 

When I find Daryl's cryptic username I'll let you know, otherwise he'll see this soon enough.

 

 

[hfrensch]

You are right Brent, but you also need to wed the tapered tops to the exhaust manifold. If you were to get it it done you would need to have another exhaust manifold already made up or it becomes a long job. To cut the tapers into the heads is relatively easy and can be done with the engine installed. The person with the jig and cutters is Wayne Johns.

 

Cheers Helmut.

 

 

[jetjr]

Jabiru can do the mod for you but need the motor back

 

If you use some high temp silicone it seems to work OK

 

Jabiru sell the gaskets and arent very expensive

 

Apparantly it was quite commin to only have them last a few hundred hours, although mine were OK at 500 - changed them anyway.

 

JR

 

 

[ianboag]

I also just blew the gasket on #1 cylinder (there was a big sooty spot in front of the cylinder). It has been recommended to me that Loctite Blue Max (aka Gorilla Snot) should be smeared on the replacement gaskets. It is a high temp silicone.

 

Does anybody know anything?

 

IB

 

 

[jetjr]

Jabiru recommend loctie CopperMAx

 

It is also High temp silicon

 

JR

 

 

[Guest Jablev2]

Hi John

 

All of the above replies are close to correct but at the end of the day you will have to do the the mod. Gaskets and salastics are only a temp fix. Be careful do not leave them too long leaking. It will run lean and extremely hot in that exhaust port and eventually it could burn through into to the rocker chamber. It is very thin in that region of the head.

 

All the Best

 

Jablev2

 

 

[Captain]

Hi JohnAll of the above replies are close to correct but at the end of the day you will have to do the the mod. Gaskets and salastics are only a temp fix. Be careful do not leave them too long leaking. It will run lean and extremely hot in that exhaust port and eventually it will burn through into to the rocker chamber. It is very thin in that region of the head. If you require the mod contact me ,I can do.

All the Best

 

Jablev2

Do you have any descriptive data that shows what the mod is?

 

And is this mod condomed by the Factory?

 

 

[ianboag]

I'm in Kiwiland. Phone no?

 

 

[jetjr]

Exhaust mod

 

This mod is strongly recommended by Jabiru, all newer engines are already done this way

 

Ill persist with gaskets until first overhaul which I expect in the next couple of hundred hrs

 

JR

 

 

[shafto]

Hmmmm this is somewhat worrying "Gaskets and salastics are only a temp fix". oh and this "do not leave them too long leaking"..... Im not trying to have a dig at you Jablev2. Its just those comments are worrying.....

 

I couldnt find anywhere where Jabiru said in a manual where welding/permanently fixing the exhaust was ok, but ill just assume so. Actually I wont even touch on that becuase i have no knowledge of what they have said.

 

But what i do know is the exhaust baffle and dump pipes are very similar in design to what a Beech 76 Dutchess have installed on them. I personally have inspected and removed 5 exhaust sytems off different aircraft in one year, becuase of leaks. 3 of them were leaks in the baffle, so a easy fix if you weld the exhuast on. BUT the other two were cracked around the flange at the head of the engine. In the case of permanently fixing, I would hate to think of the removal and cleaning/machining of the head to have it fixed.

 

Now what worrys me the most is the actually welding. The problem is your welding/attaching two different metals together. The biggest and i mean huge problem here is the metals expand and contract at completely different rates to each other. Over time you will either crack a cylinder pot or the exhuast. And that is one of the reasons for a gasket in this case. A gasket is one of the cheapest components you can replace on an engine. You really should have a spare set for a 100hrly, you may use them or you wont. But atleast you have them there. The maintanence manual on the 3300 states the system should be inspected every 100 hours. That includes the gasket. If the exhaust system is leaking the aircraft should never leave the ground.

 

A single crack on the baffle calls for it to be pulled off and welded. For two main reasons; 1 it robs the engine of power and 2; the leak leaves NoX fumes to enter the cabin. Both could lead to 'incidents'. If anyone has had a engine have a crack in the exhaust they will know what i mean by power loss. The engine runs like a dog.

 

The sealant to use is stuff called Loctite RTV (Red High Temp) you can get in from places like Aviall, Aviaquip etc....You buy it in small tubes or you may still be able to buy it in calking gun size which makes it cheap in the long run because it wont go off it you plug the end. You only need to put genuine squirt on the gasket and rub it in on both sides with your fingers. The excess will get squished out and burnt off. Also helps when re-installing keeps the gasket stuck in place :thumb_up:

 

In summary gaskets will work fine if they are used with the right sealant. You cannot re-use a paper/thin gasket but that is just what happens. Have a set of gaskets handy and you will never have a problem. Simply if there is a leak, it should be fixed.

 

 

[jetjr]

Re exhuast mods

 

I think Im reading you correctly, you may have misunderstood the repair.

 

It is simply welding a Male cone shaped fitting to the end of each exhaust inlet, this fits tightly into a Female cone shaped machined area in the head, these do not require gaskets at all and fit back on using same bolts etc. It is a method of deleting gaskets and making metal to metal seal

 

This setup makes it much simpler and more reliable and this is how exhausts are now manufactured by Jabiru. (for some time now)

 

In talking to them this was a seriuos problem on earlier engines and since this mod was introduced has solved what was a regular repair job, correctly mentioned as severely damaging to the head if flown with a blown gasket. Let alone issues with CO problems in the cockpit

 

It is an important inspection item at both 50 and 100hrly on engines with gaskets I think

 

JR

 

 

[shafto]

Ah so its sort of like a crush gasket? Or atleast a interferance fit

 

 

[jetjr]

Yep sort of, I expect the alloy is soft enough to make a good seal

 

Its a few hundred $ to have done when the engine is being worked on, Ill have mine dont at next overhaul.

 

I havent had any gaskets blow but Im told Ive been very lucky

 

JR

 

 

[shafto]

Its weird that there is no mention of it in any manuals or IPC's for that matter. Only thing i found was a note on the exhaust installation all it said was (Inlet pipes not welded in) :confused:

 

 

[Guest Jablev2]

Dear Mr Shafto

 

You have obviousley never done a Jabiru flat flange repair. I have tried all types of gaskets and salastics and believe me its only temp or the one you maybe have done is really special. The real fix is to cut a 45 degree less than a mil seat on the beginning of the exhaust port hole. and replace the exhaust flat flange pipe with ball type giving a metal to metal seal. A very good seal at that and exhaust flange leaks will be a thing of the past. Instead of having three securing bolts you only need two using the existing bolt holes. Being a ball flange they centre up nicely. I would like to know where welding was mentioned. Get a grip on it boy.:hittinghead:

 

 

[Guest Jablev2]

Its weird that there is no mention of it in any manuals or IPC's for that matter. Only thing i found was a note on the exhaust installation all it said was (Inlet pipes not welded in) :confused:

Dear Mr Shafto

Jabiru have neglected to put out a service bulletin on this exhaust flange issue so far it has all been word of mouth handed down through the Jabiru generation. Probably not a good way to do business but hopefully they will one day eventually get on top of it all.

 

 

 

[Guest Jablev2]

Jabiru recommend loctie CopperMAxIt is also High temp silicon

JR

Does not work

 

 

[jetjr]

120 hours, still OK

 

JR

 

 

[Bruce Tuncks]

Exhaust gaskets

 

I'm sure that the metal-to metal joint is better, it would also help remove heat from the head. So far I have been too cheap to do this.

 

When I was installing the exhaust pipes, there was a lot of force required to spring the flanges into position, and I thought the resulting load would be hard on the gasket. So I cut nearly through the pipe, did up the flange socket bolts without load, and tacked the cut on the pipe to be later welded at an exhaust shop.

 

Well the gaskets are ok at 300 hours, not that much I know, but if your pipes don't fit so well it may be worth a try.

 

Bruce