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 Exhaust leak question 
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Firing on two.
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Joined: August 31st, 2016, 12:12 pm
Posts: 322
Location: Hawkins County, TN. USA
Post Exhaust leak question
So I've owned my 2CV for three years now and put about 2000 miles on it. The only major problems I've had is with the exhaust system.

I have replaced the entire exhaust system on this car past the heater boxes. New crossbox (hole rusted in bottom), new silencer (guts broke up), pipe all the way back to the end of the car, new saddle clamps (crossbox to silencer clamp actually fell off!). So I've had my issues.

The 9mm bolts that came with the new saddle clamps were just barely long enough which made it a pain to get 2 or 3 threads started at each clamp in order to adjust the crossbox so it hangs off stud on the gearbox. They are not even long enough for lock washers.

I did not occur to me at the time to just go to the hardware store and buy some 5/16" X 1.5" Imperial grade 8 fasteners. Silly to pay literally dollars for metric bolts when I can get good quality Imperial fasteners for pennies from any hardware store.

I even used some of that ceramic exhaust paste that was recommended.

So my 2CV has developed another exhaust leak. AAARRRGGG!!!

Due to the multiple exhaust joints on these engines I cannot tell where it's coming from. The right hand side I know is OK, the leak is coming from the left hand side.

I can hear it at tickover with the bonnet up but it really gets loud when I start to get on it.

Question:

I don't think it's a blown headgasket, otherwise the car couldn't do 70 mph.
I would think if the headgasket was blown this car would be burning oil. it's not loosing any oil.

Is there a gasket between the cylinder head exhaust port and the elbow? The bolts are tight but the gasket could be blown out.

I think the leak could be coming from the saddle clamp past the elbox before going into the heater box. I have not tried running a stethoscope around the joints to see if I can identify which one is leaking.

I'm thinking that ceramic paste I used around the joint could have cracked. Those bolts are tight as well.

I'm thinking about trying some of this stuff instead of the ceramic paste:

https://www.permatex.com/products/gaske ... ket-maker/

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September 26th, 2019, 12:48 am
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Firing on two.
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Joined: March 21st, 2013, 12:04 am
Posts: 1048
Location: Exeter, Devon
Post Re: Exhaust leak question
The 2CV doesn't have head gaskets, or even gaskets at the bottom of the barrels. It does have gaskets between the head and the manifold.

I wouldn't think the item in the link is suitable for the exchangers joints. I have have good success with ordinary exhaust paste in those areas. put you hand near the clamps. Can you feel the blow. Have someone hold a thick rag over the rear exhaust pipe to block it an emphasise the blow. Are there signs of soot at clamps?

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September 26th, 2019, 1:07 am
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Firing on two.
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Joined: August 31st, 2016, 12:12 pm
Posts: 322
Location: Hawkins County, TN. USA
Post Re: Exhaust leak question
Roger V wrote:
The 2CV doesn't have head gaskets, or even gaskets at the bottom of the barrels. It does have gaskets between the head and the manifold.

I wouldn't think the item in the link is suitable for the exchangers joints. I have have good success with ordinary exhaust paste in those areas. put you hand near the clamps. Can you feel the blow. Have someone hold a thick rag over the rear exhaust pipe to block it an emphasise the blow. Are there signs of soot at clamps?


I felt for exhaust gasses around the joint but can't feel any. I tried wrapping a rag about the joint but the air from the cooling fan wouldn't allow me to check it. I'm not seeing any soot either.

Even if there are no head-gaskets, I suppose the surface could still leak. Looks like I'd be loosing compression.

We have this hand held machine here at work with a probe that is used to check for small chemical leaks around flanges before they turn into big ones. I think it monitors the oxygen content and if it's lower than normal indicates a leak. We mainly use it to detect acetic and sulfuric acid leaks. I'm not sure if it would work on detecting carbon monoxide. I think we have a special machine for that as well!

I could get the safety man to check my car for exhaust leaks!

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September 26th, 2019, 3:04 am
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Firing on two.
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Joined: August 8th, 2012, 11:00 am
Posts: 398
Location: Korpilahti, Finland
Post Re: Exhaust leak question
turbofiat124 wrote:
Silly to pay literally dollars for metric bolts when I can get good quality Imperial fasteners for pennies from any hardware store.

Same situation here, but other way round. Metric bolts is available anywhere for pennies, but imperial stuff is mad expensive...

turbofiat124 wrote:
I don't think it's a blown headgasket, otherwise the car couldn't do 70 mph.
I would think if the headgasket was blown this car would be burning oil. it's not loosing any oil.

Is there a gasket between the cylinder head exhaust port and the elbow? The bolts are tight but the gasket could be blown out.

As said, on 2CV engine isn't any head gaskets. Only the 375cc 9 hp, the earliest version had copper head gaskets, but none of the other...

There is a gasket between head and manifold, and they are known to burn the gasket easy. Old stuff was much reliable, but the gaskets what is nowadays made are literally crap when compared the old gaskets (with asbestos). Also, a slight misalignment between cylinder heads makes a great opportunity to have blown exhaust gasket...

If your heads aren't even, you can't have exhaust gaskets last long. No way, not any paste solve that problem. At first, take the manifold out, also gaskets out from exhaust and inlet ports, then chenk is the manifold sitting well on both heads. If not, loosen head bolts, make exact alignment, and tighten the head bolts...


About leaking between head and cylinder, these engines doesn't take any oil there. Again, this is not a Chevy small block etc. There isn't any way to get oil there, only exhaust fumes to cabin by the heating ducts...


September 26th, 2019, 9:40 am
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Firing on two.
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Joined: March 21st, 2013, 12:04 am
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Location: Exeter, Devon
Post Re: Exhaust leak question
TF
Confirm its exhaust and not induction.

Try just reseating all five exhaust clamps. Clean them up and check for soot.

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September 28th, 2019, 11:13 am
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Firing on two.

Joined: June 22nd, 2014, 8:09 pm
Posts: 703
Location: Reading, Berks UK
Post Re: Exhaust leak question
Yes definitely try the clamps, I would. I like the Burton style ones. Bit expensive, good though. You can use grease to get them to seat properly. I don't use exhaust paste at all, it doesn't seem to last long on these.


September 29th, 2019, 11:31 pm
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Firing on two.
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Joined: August 31st, 2016, 12:12 pm
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Location: Hawkins County, TN. USA
Post Re: Exhaust leak question
I got these clamps from Burton's. I even took a rotary wire brush on my drill and knocked down all the old paste, rust and pits to a smooth surface before installing the clamps and the paste. This time I won't use any of that paste and see what happens. I'm thinking perhaps the paste has cracked causing a leak.

I picked up some 5/16" X 1.5" bolts, nuts and lock washers the other day from a hardware store so I don't have to struggle.

I didn't have time to fool with any car projects this past weekend. The wife wanted me to get rid of that nasty carpet in the sun room and put down vinyl flooring (12 X 18'). So I was knee deep in that project for almost two days.

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September 30th, 2019, 5:35 pm
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Joined: March 21st, 2013, 12:04 am
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Location: Exeter, Devon
Post Re: Exhaust leak question
Get it all cleaned up and sat in place. Start from the front and work back. Ensure that nothing is stressed. Check the heat exchangers are sat over the engine shrouds correctly. I have had good success with tapping the clamps a little with a hammer so they seat better and not rely fully on the bolts pulling the pipes together.

Don't forget the swan neck to cross box clamp.

Take your time. :D

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If you can't fix it with a hammer, it's probably electrical (or, an electric fuel pump!) ....


September 30th, 2019, 6:54 pm
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Firing on two.
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Joined: February 11th, 2009, 12:32 am
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Location: Chichester, West Sussex
Post Re: Exhaust leak question
Never ever use exhaust paste. Burton Clamps are all you need, smeared with a little copper grease.

It's very easy to tell if the joints are leaking; put the choke on and hold your hand near a joint. Any leak and you'll feel the air puffing. Blown gaskets are evidenced by black 'soot' around the base of the manifold.

The sound is different for different leaks too.

If it sounds like a Spitfire (or maybe a Mustang?), and smells 'hot' it'll be manifold gaskets.
If it sounds like a steam train (or, I dunno a 'railroad locomotive'?) its likely to be the heat exchanger joins.
That sort of moist farty noise that makes you think about changing your pants? That's what a dead crossbox sounds like.
If its more of a deep thumpy noise like a deranged child hitting a drain pipe then it's probably the torpedo joins.


September 30th, 2019, 11:46 pm
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Joined: March 6th, 2009, 1:40 am
Posts: 3675
Post Re: Exhaust leak question
Sam,
aren't you having a bit of a laugh with all these 'orchestral overtones'?
.
Whenever I've used a 1 metre length of windscreen washer tubing to track down and locate an exhaust system leak with pinpoint accuracy, none of the 'variations on a theme' which you've mentioned have ever been apparent.
.
Anyhow, have I been missing out on some sort of existential experience? ;)

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October 1st, 2019, 1:15 am
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