Heat exchanger "leakage" or blowby on the headers??

[chrisbruck]

I've been messing with my stock heating system to make sure all the heat is actually making it to the cabin. I was messing underneath checking the hose connections and found a large amount of air blowing out of the actual heat exchangers where the metal housing surrounds the headers. Didn't feel normal but they are 28 years old.

Is this "normal"? Anyone else notice this?

Can I wrap the edges where they leak with some muffler heat wrap to help keep the air flowing to the cabin?

[zedsn]

My car isn't on the road yet but I have early heat exchangers with the 3 fingers to the pipe that goes to the muffler on either side and I noticed water dripping out of them the only time that I have started the car so your exchangers may be built the same way with an air gap from the factory.

[jtsilverfox]

I'm about to reinstall my HEs and was wondering also about that gap btwn the 3 header pipes and where they go thru the sheet metal. I notice in all the pictures I've seen that this seems to always be the case. Is there a reason they're not sealed? Zedsn mentioned the possiblility that the gap is intentional to perhaps provide a place for water to blow out. But, that gap would seem to be a lousy way to do that. And it seems to me that it would be a place for fumes from oil drips on the HEs, smoke, etc to enter the heating system (altho the fan would provide a positive pressure to keep that crap out of there).
I'm thinking of sealing them up as Chris mentions (welding, JB weld, or muffler wrap).
I'm still searching the forums on this but haven't found anything yet. Any thoughts?
cheers,
jt

[redridge]

heat exchangers are not a sealed system, if they were, you will see welds on them... if you look at the heater box (flaps)... they essentially do the same thing. But, if those gaps are wide... they are not efficient delivering heat to the front of the cabin... hence all the blowers porsche used. As far as dripping oil on them... yes you will get fumes, but that is an indication that you should fix the oil drip and not an issue to the heat exchangers.

[Pazuzu]

I assumed they were not sealed because of high temp expansion. The pipes are heater temps (many hundreds of degrees) while the shell is, what, 200 degrees? There must be lots of flexure between them, if they were sealed it would crack the first time.

edit: I think header tape would work, it would allow differential flexing while mostly sealing that area.

[haggis780]

[QUOTE=jtsilverfox;8725702]I'm about to reinstall my HEs and was wondering also about that gap btwn the 3 header pipes and where they go thru the sheet metal. /QUOTE]

I have mine off right now and had a look. 88 911 - i don't have those gaps but the fit around the exhaust is far from sealed. Was wondering if you had any oil residue inside the exchangers? I did on mine when I pulled them.

[jtsilverfox]

Mike: Yeah, I was wondering about the heat cycling/diff cracking whatever you put on them. However, upon looking at mine again, I see that I did try some JB Weld years ago on a few spots that I could access while they were still on the car. And they seem to have held. Also, I've since seen a couple of photos that seem to show others have tried it and seem to have held (don't know though how many miles they've got on them...
Haggis: Don't know if there's any oil residue inside. How did you ck - just tip them and see if any pours out? My HE's have been off for many years and seem completely dry now...
cheers,
jt

[haggis780]

When I had the headers off the car I just wiped into the HE with a rag at the lower open end and there was quite a bit of oil on the rag. I did have oil leaking above the HEs from broken head studs - but I am not quite sure how the oil would have ended up inside.