98 V70 exhaust leak diagnosis

[98v70dad]

I've been looking for a leak or crack in my exhaust but so far haven't been able to find anything. Tonight I thought about taking low pressure compressed air (5 psi say) and making a plug for the exhaust so I could pump the air into the tail pipe. With the car not running I could get up under the car and listen for whistling air from any possible leaks or cracks.

I don't know how effective this would be but can anyone think of a reason not to do this? In other words could I damage something by doing this? I'm not sure, but I think it wouldn't cause any damage.

[wizechatmgr]

You could run seafoam through it to similar effect, except it'll be like running a smoker on the inside of the pipe...

I doubt you'd damage anything by using compressed air, but unless your exhaust system is welded from end to end, you're going to have small leaks that may send you off the path of Volvo utopia.

[98v70dad]

You could run seafoam through it to similar effect, except it'll be like running a smoker on the inside of the pipe...

I doubt you'd damage anything by using compressed air, but unless your exhaust system is welded from end to end, you're going to have small leaks that may send you off the path of Volvo utopia.

Thanks. I already did that. Past seafoam treatments produced a huge cloud of smoke from the area of the exhaust manifold. The treatment I did with the heat shield removed to pinpoint the possible leaks/crack produced NOTHING. GO figure ...

[scot850]

There are a few possibilities:

1) Failing flex pipe
2) Crack in the manifold - this can be frustrating to find in early stages as it can 'seal; when warm or be sealed when cold and open when warm.
3) Exhaust manifold gasket(s) failing. Again not unheard of with these older engines and the manifold gaskets start to degrade.

Neil.

[98v70dad]

There are a few possibilities:

1) Failing flex pipe
2) Crack in the manifold - this can be frustrating to find in early stages as it can 'seal; when warm or be sealed when cold and open when warm.
3) Exhaust manifold gasket(s) failing. Again not unheard of with these older engines and the manifold gaskets start to degrade.

Neil.

[98v70dad]

There are a few possibilities:

1) Failing flex pipe
2) Crack in the manifold - this can be frustrating to find in early stages as it can 'seal; when warm or be sealed when cold and open when warm.
3) Exhaust manifold gasket(s) failing. Again not unheard of with these older engines and the manifold gaskets start to degrade.

Neil.

Any thoughts on putting low pressure air up the tailpipe to listen for hissing air? I don't want to cause any damage - that's what I origionally asked about. I've already visually inspected each of those places you mentioned as thoroughly as possible and didn't find anything

[scot850]

Good question to which I can say I just don't know the answer to. I can't think what damage it could cause as exhaust gases come out the end and there are no one way valves in the muffler. You might want to remove the spark plugs to allow pressure to dissipate if a valve is open and not pressurise the block. I suppose you could leave the plugs in but don't go crazy on the pressure or length of time you subject the engine to.

Use a piece of tissue attached to a short stick to give you the ability to move it around the manifold and muffler to find any leaks. Make sure you try to get it under the manifold and the gaskets to the cylinder heads.

Neil.

[98v70dad]

You could run seafoam through it to similar effect, except it'll be like running a smoker on the inside of the pipe...

I doubt you'd damage anything by using compressed air, but unless your exhaust system is welded from end to end, you're going to have small leaks that may send you off the path of Volvo utopia.

Hit hit the nail on the head about the clamped connections. The connection right after the catalytic converter and forward of the muffler is leaking like crazy...almost like there is a hole in the muffler. Is it supposed to leak like that? The amount of air coming out of the joint was as if there is an 1/8 inch gap all around...a lot of air was coming out of the joint.

I used a shopvac with the hose on the exhaust side (blowing air) and shoved up the tail pipe. The pressure produced isn't much but the shop vac is able to provide a good volume of air so any leaks are obvious.

[scot850]

Excellent! Good thinking and hopefully that is the main issue. The mufflers have a ball and socket type connection at that point behind the catalytic converter. That 2 piece clamp does rust and wear which allows the pipe to move. IF and I do mean IF you can undo the 2 nuts then remove it and check the condition of the 2 ends. You could sty cleaning the clamp up and try a little exhaust cement to 'fill-out' the space between the clamp and the joint. Realistically you may have to buy a new clamp. Be careful if you buy a new clamp from Volvo as they list the wrong bolt for the clamp on Vida.

Neil.

[wizechatmgr]

Hmm, makes for an interesting idea for next time I need to smoke a car... Smoking wood chips dumped in a metal smoker box placed in the shop vac.