Cracked Headers

[lukeh]

How can a person tell if their headers have cracked in a place that is not visible without having to take them off the car? Are there any obvious symptoms a person would notice?

[356-930]

Originally Posted by lukeh

How can a person tell if their headers have cracked in a place that is not visible without having to take them off the car? Are there any obvious symptoms a person would notice?

Yes, you will hear an exhaust leak, especially when the engine is cold. If a small crack, it will usually seal itself with expansion from heat. If your engine gets quieter as it warms up, probability you have an exhaust leak is high.

[lukeh]

What sound would it make? Some popping?

[sand_man]

In many cases, it sounds like you're driving an early air-cooled beetle....

[sand_man]

Might also look for signs of exhaust carbon/soot.

[stownsen914]

Another option, which I used to do a lot of in my 914/4 ownership days to diagnose exhaust leaks ... take a several foot length of small diameter hose, like fuel hose, and use it sort of like a stethoscope for exhaust leaks. Put one end sort of near your ear (not too close!), and probe around the suspected leak area with the other end of the hose. When you get near a leak, you'll hear a clearly audible puff-puff sound. Works like a charm.

Scott

[NathanUK]

I'm just guessing here but if you turn on your heater to defrost and aim only at the screen, if it's leaking you should get vapour on your windscreen?

Plumbers check gas flues with a mirror, any steaming up and you know it's leaking fumes...

Try it out on the tailpipe to see if my theory is correct.

[sand_man]

BTW, what type (brand) of "headers" are we talkin' 'bout?

[gogomobil]

I once had a leak and it made a tap-tap-tap-tapping noise.

[WERK I]

Originally Posted by 356-930

Yes, you will hear an exhaust leak, especially when the engine is cold. If a small crack, it will usually seal itself with expansion from heat. If your engine gets quieter as it warms up, probability you have an exhaust leak is high.

Actually, my B&B's make noise when the engine is fully up to temperature. The noise a leaky header makes sounds very much like a noisy rocker, that is, if the cracks are small.
Visually, you'll see white traces where the hot exhaust is escaping. Must common areas are the slip joints, welds for the heater boxes and collectors.

[BoxxerSix]

Originally Posted by WERK-I

Actually, my B&B's make noise when the engine is fully up to temperature. The noise a leaky header makes sounds very much like a noisy rocker, that is, if the cracks are small.
Visually, you'll see white traces where the hot exhaust is escaping. Must common areas are the slip joints, welds for the heater boxes and collectors.

Yea those B&B's with heat always seem to crack right at the spot tig welds where the affix the sheet steel that forms the heater boxes. Wish-wash headers in my opinion

[blown daytona]

At the shop we have a smoke machine. Pump the smoke into the tail pipe and shine a spot lamp around to find the source of the smoke. Saves getting burnt on hot exaust.

[WERK I]

Originally Posted by BoxxerSix

Yea those B&B's with heat always seem to crack right at the spot tig welds where the affix the sheet steel that forms the heater boxes. Wish-wash headers in my opinion

I don't know. I haven't had any other types of manufacturer's headers on my car, but these held up over a period of 6 years. No track days, btw. I don't like any of the heater box designs by GHL, B&B. They weld the boxes across all the tubes which is a disaster waiting to happen. FabSpeed has new headers out, but they appear to be of same design as the others.

[fredmeister]

Originally Posted by WERK-I

I don't know. I haven't had any other types of manufacturer's headers on my car, but these held up over a period of 6 years. No track days, btw. I don't like any of the heater box designs by GHL, B&B. They weld the boxes across all the tubes which is a disaster waiting to happen. FabSpeed has new headers out, but they appear to be of same design as the others.

Can you explain why this causes leaks? I know the weld if improperly done could blow a hole thru the tube but would not they find this during the final inspection?

[WERK I]

fredmeister,
It's not that there's an apparent flaw in the welds, it's the heat cycles the headers w/heat boxes go through. The very hot header tubes are expanding at a different rate than the cooler heater boxes. The expansion and contraction routines these headers go through will weaken and then crack the weld at the box, or worse, crack at the header tube, creating a hole.
If I could get an alternative heat source (don't need a lot...not driven in winter), I would definitely use headers w/o heater boxes

[930gt-40r]

Plus 1 on what Dave says- did you see the ones that GSF has? They weld all the way around the primary to the heater-box! At least my old B&B's have a small tack-weld that may have a little give to it. As far as heat-sources go, I have been toying with the idea of an electric coil type heater, but dont want to strain the alternater. Then I have even thought of making a "heater core" that had oil pass through it, but it would take forever to get hot. If anyone has any ideas for this, please let me know.

P.S Protomotive makes a collector that goes over the stock engine mounted oil-cooler and gets hot air from there, unfortunatly I am doing away with the engine mounted oil cooler.

[spence88mph]

Kris, I recently tried to get one of the Protomotive engine mounted oil cooler boxes and got this reply from Todd (he's a good man, always replies straight away):

"We’ve found a simple plate hung off of the rear tin that draws heat from the back of the cylinder head to be just as effective and stopped manufacturing the oil cooler heaters."

I replied asking for more info and if he would fab one for me and got this back:

"No, sorry we’ve just fabbed them when we need them on the cars. I don’t have any fixturing for them, nor any older 911’s around to even fab one on. We seem to be doing only 996tt/997tt’s lately.
A simple plate, hanging down from the rear sheet tin with a tube welded on the back that you can attach the heater duct to. It’ll just draw the hot air coming off of the bottom of the cylinder head and exhaust system."

I'm going to give it a try, just can't get my head around it right now, man the car didn't do many miles this last winter, too cold in there. I've been meaning to ask Brian if he can fab something like this up. You persisting with your car Kris?

[930gt-40r]

Yea Spence- I couldn't stay away from it. I ended up getting a set of nice cyls and actually spent the money on the head work and am now re-assembling her this week. I swear, these cars have to be more expensive than drugs and are more addictive. I should have her done in a few weeks- thank you for asking.

[RarlyL8]

SSI makes the only 930 heat exchanger I know of that actually produces good heat and does not have welded primary joints within the exchanger housing.
They aren't OBX/GSF price point; you get what you pay for.