Think this is an exhaust leak?

"Chairman Kaga" (mike-mckinnon) 11/23/2015 at 10:42 • Filed to: None

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I finally got my Alfa slapped back together after more than 6 months of work.

Rebuilt passenger side head

Valves to factory spec

New timing belt and water pump

New fuel pump

New fuel hoses and clamps

New vacuum hoses

New battery

New Bosch connectors for the injectors, cold start injector, thermo time switch and cold start sensor

Cleaned and repaired grounds

Cleaned and repaired power cables

New ignition coil

New spark plugs

New gaskets (head, valve covers, exhaust manifold)

Everything set to proper factory torque

All components tested - alternator, temp sensors, oil pressure, fuel pressure regulator, etc

The thing starts in less than 3 seconds and idles at exactly 900 RPM. However the passenger side exhaust manifold flange was pretty badly rusted, and one of the flange bolts was so corroded it was about a half-inch shorter than the other. Based on some feedback from the AlfaBB I think I have a small exhaust leak. Hear the thrum? They say an exhaust leak in these engines can sound like bad valves, which I know I don’t have.

How would you guys test for that? I’ve seen folks stick a shop-vac up the muffler and use a stethoscope to listen for a hiss. I’ve also seen soapy solutions on the suspected leaking zones, with the bubbles revealing the leak. Other guys just say pull the manifold (it’s surprisingly easy on this car), wire-wheel it, replace the studs with bolts, then bench test it with a vacuum.

Thoughts? This is literally the last thing I need to resolve before I attempt a road test.

crowmolly > Chairman Kaga 11/23/2015 at 10:49

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That certainly sounds like an exhaust leak to me.

Does it speed up when you rev the engine? Any carbon around the flange area? Did you check the manifold flange(s) for flatness?

Chairman Kaga > crowmolly 11/23/2015 at 10:52

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Yeah, it matches revs. I haven’t noticed any new carbon around the flange but I JUST got the thing running reliably yesterday and didn’t really have time to dig back into the exhaust. I should probably just pull both sides and rebuild the flange hardware, huh? I just have a feeling that’s where the leak is.

I also blew a ton of flaky carbon out of the muffler the first time I started it up. I figured it was just gunk from the muffler (these stock Alfa pieces are known to rust inside out).

Steve in Manhattan > Chairman Kaga 11/23/2015 at 10:54

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What sort of Alfa? Jealous, although it appears more of the line will come to US America.

crowmolly > Chairman Kaga 11/23/2015 at 10:58

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Yeah, sounds like you need to take it back down, but try re-torquing the fasteners first if they are bolts. Sometimes it will take a few heat cycles for the gaskets and bolts to hold the right amount of torque.

If it’s a royal PITA to pull the manifold you can try the cigar trick, where you light a cigar, put it in the end of the exhaust pipe and cap it watching for any leaks (with the engine off of course).

Chairman Kaga > Steve in Manhattan 11/23/2015 at 11:25

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It’s an ‘82 GTV6.

Chairman Kaga > crowmolly 11/23/2015 at 11:28

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Well, according to the AlfaBB, I really should’ve replaced the studs while I had it out. They actually recommend pulling the old flange studs but only replacing one of them, and use a shoulder bolt on the other side. Makes it much easier to get the thing properly aligned.

But I’ll try to just test for leaks before I go to that trouble. I really want to drive the damn thing!

Steve in Manhattan > Chairman Kaga 11/23/2015 at 11:29

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Nice!

crowmolly > Chairman Kaga 11/23/2015 at 11:33

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One other question:

Do they make upgraded gaskets for this engine? Sorry but I’m not familiar enough with Alfa stuff.

Definitely re-torque first if it’s a PITA.

Chairman Kaga > crowmolly 11/23/2015 at 12:04

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Not really. It’s a perforated metallic “squash” gasket. The new ones looked exactly like the old ones, just... new. I didn’t see any alternatives on any of the parts suppliers’ sites.

gmporschenut also a fan of hondas > Chairman Kaga 11/24/2015 at 07:20

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As Crowmolly said I would try retorqueing them first. On my 914 I went to re-torque after a couple drives after re-installing the engine. Got about 1/8 turns on 6 of the studs and 1/2 a turn on the other 2. Also did you evenly torque the gasket? I mean did you hand tighten all the nuts first to seat the gasket, then toque to 50%, 75% 100%? I cringe when I see people just grab the torque wrench and torque one at a time.

Chairman Kaga > gmporschenut also a fan of hondas 11/24/2015 at 10:28

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Yeah, the way the flange is designed the nuts have to be tightened evenly. A few turns here, a few turns there. But I’ll be getting back underneath over the holiday and checking it out. I think I might remove the zinc nuts and replace them with brass, though. Less chance of stripping what’s probably weakened threads on the original studs and also less chance of seizing.