Exhaust leak?

[vtluu]

Ever since this morning (when I changed sparkplugs) I smell exhaust fumes every time the car sits still (at a traffic light, in my driveway, etc.). I checked the sparkplugs and double-checked that they're torqued properly--they are. What else could it be? I can turn up the ventilation and it still smells--in fact it's as if the smell is coming from the vents. I'm starting to suspect an exhaust leak forward of the cat (since if it were behind the cat it wouldn't smell so nasty--once my HFC is heated up to temperature the exhaust gases from the tailpipe don't smell at all). How does one go about isolating (locating) an exhaust leak?

Car is running normally in all other respects.

[300kpa]

If your exhaust is leaking, you should see the flange got blacken. CHeck to see if there is sign of leakage. If so, take it out and fix it with hi temp silicone. I found it more reliable than the metal gasket.

[EVO GRIM]

Theres a trick of spraying something on the spot you suspect, the sound changes or something. Best to get under there and check all connections. Maybe your hi flow has gone bad. I always smell exhast at lights with the windows down but I dont have a cat.

[MarkSAE]

If the leak is coming from before the cat, then you should take off you downpipe and inspect the welds and flanges for leaks. You'll be able to see black soot around the leak, whether it's on the gasket, welds, or flanges.

BTW, it's normal to smell exhaust fumes at the tail pipe before the cat warms up.

[earlyapex]

Theres a trick of spraying break cleaner I think on the spot you suspect, the sound changes or something.

Spray brake cleaner on hot exhaust components?

errr........

[MitsuMan]

yea make shure you spay the cat really good and have a fire extinguisher on hand when you do(please don't do this)

:lol: just listen and if you can't Isolate it then get a piece os 5/16 fuel hose and put it in your ear and then waive it around the suspected area
or (not the best way but most effective) induce a little ATF into the intake at a vacume sorce and then you'll see a lota smoke from where the leak is oh do this in a well ventalated area!!!!!!!!!!!!!

[zyounker]

Theres a trick of spraying break cleaner I think on the spot you suspect, the sound changes or something. Best to get under there and check all connections. Maybe your hi flow has gone bad. I always smell exhast at lights with the windows down but I dont have a cat.



Please edit your post and remove this comment.. THis is not the case and very dagerous.. Brake cleaner is flamable and could cause a fire if sprayed on the exhaust.


You are thinking of using water on the intake track to look for leaks.. (Some people use brake cleaner as well, but i would not recommend it.)

[MarkSAE]

Not to mention the fumes from the brake cleaner can make you pass out.. haha

[EVO GRIM]

s)

induce a little ATF into the intake at a vacume sorce and then you'll see a lota smoke from where the leak is oh do this in a well ventalated area!!!!!!!!!!!!!

Oh yea thats the trick!

Leave it to an ex- Fireman! Job security.

[vtluu]

Thanks everybody. Guess I got some wrenching to do Sunday. :(

[vtluu]

So... Following the "undo the last thing I did" philosophy, I put my old sparkplugs (NGK BPR7EIX) back in. Idled my car in the driveway for a few minutes and guess what? Exhaust smell in the cabin, gone.

Bad seal on one or more of the plugs? I inspected the BPR7ES plugs and (a) they seem to have a lot of blackening near the tips for plugs that have only used for 3 days (too rich?), (b) I can see what looks like soot caked between at least one of the plugs and its crush washer.

Oh and I had gapped the BPR7ES plugs to 0.029"... assuming my gap tool is correct. That's suspect too because according to NGK's site, they come pre-gapped at 0.032" and yet I had to increase the gap size to get to 0.029". Supposedly the BPR7EIXs come pre-gapped at 0.032" also and I never changed the gap on those (and the car works just fine).

Leaky plug? Too much/too little gap? Running too rich (but why only with these plugs)?

[earlyapex]

Oh and I had gapped the BPR7ES plugs to 0.029"...


That's way too much for BPR7ES. I use 0.026 with stock ignition.

How did the car perform with that gap? You where probably getting unburned combustion cycles which led to the gas smell.

Iridiums should never be gapped, they come pre-gapped. Gapping them could break them.

[vtluu]

That's way too much for BPR7ES. I use 0.026 with stock ignition.

How did the car perform with that gap? You where probably getting unburned combustion cycles which led to the gas smell.
Do you find you have to increase or decrease the gap size from the stock BPR7ES gap to get to 0.026"? I think that's just about what it comes with.

As I said the car seemed to be running normally--I didn't hear misfires and it seemed to pull okay on the freeway and on-ramps.

[evo_dadi]

when i got me a new set of bpr7es plugs it was already gapped at 0.26 when i measured it so i left it alone.im with bryan also you would want the gap a little closer together than apart to give you a bigger spark to burn the fuel better.

this happens to me once in a while also but everytime i check around the flange/gasket areas there's no sign of leaking.

[RT]

....soot between the crush washer and the plug? Plug not seated all the way?

[earlyapex]

Do you find you have to increase or decrease the gap size from the stock BPR7ES gap to get to 0.026"? I think that's just about what it comes with.


Most sets are set around .029-.030 out of the box. I usually have to bring them down to .026

I think I've probably gapped at least 100 sets of those damn plugs over the last 7 or so years. :?

[vtluu]

Looks like I spoke too soon. Even with the old plugs I still get the exhaust smell in the cabin. There's another clue I'm investigating--a bit of light-coloured "residue" on the middle of the front edge of the spark plug cover. It first appeared after my track day at Willow Springs I think; I thought I cleaned it off last night but it was back again. It could be my imagination, so I'll confirm it first (and take a photo).

[earlyapex]

Looks like I spoke too soon. Even with the old plugs I still get the exhaust smell in the cabin. There's another clue I'm investigating--a bit of light-coloured "residue" on the middle of the front edge of the spark plug cover. It first appeared after my track day at Willow Springs I think; I thought I cleaned it off last night but it was back again. It could be my imagination, so I'll confirm it first (and take a photo).

hmmm. Blew your headgasket? :shock:

Check your cam seal, its a half circle looking rubber thing on the side of the valve cover. Also check to see if you have any residue in the spark plug holes.

have you sniffed around the engine bay when the car is on? Can you smell the exhuast smell then?

Also, you had a thread about drilling a hole into your cabin to route things from the engine bay, did you do that yet? Did you seal it up after?

[RT]

Don’t know what you may have for tools but a basic compression gauge is cheap and compression should be checked. Also take a look at the radiator water and coolant overflow tank for signs of oil film floating on the surface of the water or coolant. 8)

[MarkSAE]

Don’t know what you may have for tools but a basic compression gauge is cheap and compression should be checked. Also take a look at the radiator water and coolant overflow tank for signs of oil film floating on the surface of the water or coolant. 8)

Yep. I agree. For someone who tracks his car as often as Tam, I would highly recommend checking your compression every so often. A compression checking gauge is like $20 from Sears.

[vtluu]

Thanks, a friend of mine has one and I think I might still have it (we used it to check the compression on my VW rally car).

[vtluu]

Found it:

http://imagenode.com/oh

That was the gasket between the cat and downpipe. Let's hope it's tightened enough this time, that nut is a real b**ch to get to with a torque wrench.

[earlyapex]

Found it:
That was the gasket between the cat and downpipe. Let's hope it's tightened enough this time, that nut is a real b**ch to get to with a torque wrench.

ahhaha, you used a torque wrench down there? Get any photos of you doing that?

Just he-man tighten them down with a normal wrench. Those are big ass bolts.

[MarkSAE]

I torque wrench mine down if I can since my human torque wrench isn't always accurate. ;) But if there really is not room, I'll just do the he-man thing.. haha

[RT]

Flanged connections won’t give up the condensation as easy as slip together pipes but sometimes an early sign will be small drips of water on the garage floor under the gasket or connection that’s givin’ up.

Agreed, on that connection, put a closed end wrench on ‘em and give ‘em a couple raps with a rubber mallet just for GP. :wink:

[vtluu]

Well, apparently I didn't wrench hard enough or I need to do something different because I still get exhaust fumes in the cabin--not as strong as before but still there. Is there some kind of sealant I can put on the gasket/flange to ensure a leak-proof seal? And/or should I get a new gasket?

[MarkSAE]

Is your flange warped? I assume this is the flange between the downpipe and the cat.

[egui42]

Well, apparently I didn't wrench hard enough or I need to do something different because I still get exhaust fumes in the cabin--not as strong as before but still there. Is there some kind of sealant I can put on the gasket/flange to ensure a leak-proof seal? And/or should I get a new gasket?

You need to start working out!!

[vtluu]

You need to start working out!!
:lol: Work smarter, not harder:

http://www.permatex.com/images/catalog/special/80335.jpg

[RT]

Always use a new gasket, an OEM style with the crush area is prefered. Helps take up the slack so the speak in the flanges. Gasket is always prefered over sealer but there are some very good hi temp sealants out there nowadays. But if the flanges are little out, sealant comes in all sizes. :lol:

8)

[RT]

...and thats some good sealer. 8)

[zyounker]

If the exhaust is not lining up well you may want to try using 2 exhaust gaskets.. Common work around on WRX downpipes that works well.

[vtluu]

Dropped by WORKS and Tyler had a quick look. He noticed right away the crank case breather on the back of the valve cover had come off :oops:; there was oily residue sprayed lightly all around it. Don't know how I missed it or how long it's been off--judging from the amount of residue, not more than a few days. Not sure how it came off either. Anyway we put it back on, and now the exhaust fumes smell are gone even though I haven't touched the gasket again (although I'll be replacing it as well, just to be sure). So it seems that although there was a leak in the cat/DP gasket, it wasn't the cause of the problem I observed. Thanks Tyler! :worthy: