exhaust leak or something else?

[eufo]

i've got an odd thing going on with my car... at first i thought it was an exhaust leak, now i'm not so sure... to preface this, all times mentioned are with the windows up and a/c on... radio off to listen closely...

since i've been driving the car daily (about a week or so) on the freeway it was making what sounded like an exhaust leak under load coming from the engine area... i didn't think much of it and figured i would reseat the headers eventually or tighten them up...

yesterday was extremely hot outside... i drove the car into work (30 miles), and didn't hear the supposed exhaust leak at all! nothing! just pure exhaust from the pipes... which i was extremely happy with... but confused...

today it was cooler when i left for work... and the exhaust leak sound was back... all the way up here to this part of town... i stopped at home depot on the way in... afterwards it started getting really hot out again... as i drove from home depot to work i could tell it was getting hot, because i was burning up... suddenly the engine began idling a bit different (lower) and the "exhaust leak" disappeared as suddenly...

i'm worried there is something else going on here... not an exhaust leak at all... could i be hearing detonation??? if so, what might the outside temperature have to do with it? bad IAT sensor? any ideas?

 

[94-302-vert]

I have an exhaust leak that I hear for the first couple minutes then it goes away... Started after doing my clutch and I haven't gotten around to tightenting the H-pipe yet.... So don't rule that out....

Detonation should get a lot worse as it gets hot and humid out, never better...

 

[eufo]

Detonation should get a lot worse as it gets hot and humid out, never better...

given everything else equal, that is true... but i'm wondering if the ambient temp is somehow creating a timing change that could be creating detonation under certain conditions...

 

[eufo]

side note: EGR eliminated improperly (capped off), 93 octane BP Ultimate, 12* ignition advance

 

[bill302]

i would check and tighten the header bolts and see what that does...i had the same problem that changed with motor and outside temps and i had 1 loose header bolt....tightened it and it was fixed....

 

[BlackVert]

as the engine and pipes get hot they tend to expand. that may close up a small leak that is open when they are cooler.

 

[eufo]

yeah, i'm going to go ahead and tighten up the header bolts... is this better to do when the engine is still a little warm or wait until its completely cooled off?

 

[bill302]

a little warm wont hurt as long as its not hot enough to burn you...

 

[BlackVert]

i think it's a 3/8" wrench

 

[stangz4life]

yes i would deff go with what blackvert said.when you first start driving everything is cold as you drive the headers and whole exhaust system gets extreamely hot and im sure it expands a lil bit to seal up what lil bit of a leak you prob have.if possible try to do as warm as possible.

 

[BlackVert]

i would say do it as cold as possible before it expands. that way you'd have more room to turn the bolt more

 

[95vert354]

If your driving and you think you here it leaking try a down shift and let the motor slow it down ,giving it no gas. Most times if it is an exhaust leak, especially at the header ,you will get a popping or slight backfire through the exhaust. If it does you'll know for sure it's a leak.:SNSign:

 

[stangz4life]

hm i was always told that you should do tighten when hot ..just like header bolts.

 

[BlackVert]

hm i was always told that you should do tighten when hot ..just like header bolts.

you're probably right, it just seems to make more sense to me the other way ...

 

[1TallMF]

I was thinking cold makes more sense too, but I have heard the old tighten-when-hot ritual. Seems to me if you tighten when hot, it will just shrink as it cools down, decreasing the tightness

 

[94-302-vert]

I belive in retighten when hot...

Ever notice that the oil filter comes of 100 times easier if the engine is warm?

Heat allows the clearance btween the bolt and head to topen up, plus the bolt grows in length allowing more room to tighten...

 

[BlackVert]

yeah ... that makes sense ... i guess ... the block expands more than the bolts so the holes are bigger ... making it easier to get the bolts in farther ...

 

[VibrantRedGT]

Paul, does it make the sound in neutral too (no load)? Exhaust leaks if bad are usually constant. Under a load more vocal obviously. I was trying to rule out detonation. Ticking noises in hot conditions under load could be lifters, exhaust, detonation, injector, etc. Need to rule out a couple of these.