Further questions !

I have tracked down some used heat exchangers. But before I go ahead and start replacing things and then finding out I am still at square 1 (like almost everything else I have done on my car). I would like to see If I can confirm my suspicions in any way ?


1) Is it possible that the air I am feeling is the air that the fan is producing comming through the bottom ?

2) If I take it to a mechanic to put on a hoist is there anything they could do to check out the heat exchangers ? and

3) lastly is there any way to check used heatexchangers to see if they are any good ?

JK: points 1 through 3 can be checked out by a mechanic. I'd just make sure the person is a Porsche mechanic, and not some second-hand Holden or Falcon wrench. I've found that feeling for air or listening for noise is nearly impossible with a 911, particularly a 2.7, since they have a noise all their own: they "howl" more than any other 911 engine, which is cool but hard to decipher anything from.

My old 2.7 had so many rattles and such to it (in addition to "the howl"), I could never make heads nor tails of what was going on.

Give yourself some peace of mind, and get it checked out. Don't think. Do. If the heat exchangers are bad, they'll prove so while on your car. If they're good, the mechanic will have already bolted them in place with good exhaust gaskets. If they're bolted in with good exhaust gaskets, you won't have any exhaust leaks. Additionally, I'd make sure your muffler is up to snuff. After that, all you should hear is that 2.7 "howl," which is a good thing. :)

O.K
I did something stupid !

When replacing the valve covers after the valve adjustment I used new gaskets, new washers and lightly sanded the lower covers on a plate of glass. The problem is that I reused the old nylock nuts(with a-bit of silicon) and I didn't sufficiently clean the mating surface of the engine as the previous owner used silicon on the old gasket. ( I cleanred it well but not perfectly).

Now (as you may have guessed) it still drips some oil ! Particularly from the nuts !


Q ?

Could I just replace the nuts with new ones or would I have to get a whole new set of gaskets and washers as well ?

jk: I'm not at all a DIY-er to the extent you are (though I may give a try soon :) ), but if it were me, I would have at least installed new gaskets. Give that a try, but make sure the mating surface is fairly clean.

How much sanding did you do?
Is the oil leaking from the valve covers?

JK,

You should be able to get away with just new Nyloks. If you have over-torqued them, though, you may also need new aluminium crush washers and possibly even gaskets. Search the archives for the correct torquing specs. I think it's 8 or 10lbs/ft, but please double check before doing it.

I wouldn't sweat it, though, it's a learning experience! I cleaned my surfaces with a knife and then lightly sanded and it's drip-free! :D

I did use new gaskets.

As for sanding the covers I used 240 git then 400 git then 600 git

They were surprisingly smooth and flat !

I torqued them (some at) 6 Lb/Ft as recomended in 101. But my torque wrench is huge and wouldn't fit well in most positions so I resorted to doing it by quess. I probably over torqued them rather than undertorqued them.

I should of used carb cleaner to remove all the old film of silicone, but i didn't have any at the time !.

I don't even think the covers are leaking other than from the nuts !

John,

You've inspired me to attempt my own major service! Great news about the studs!


Matt Holcomb
MFIWDP
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Lots of issues raised here, too many to cover well, but I have these comments:

DO NOT overtorque heat studs, particularly on a magnesium case engine. Go to 24 lb-ft and no more. If no one but you has touched them in quite a while, and if they just needed slight tightening, then this is indeed a good sign.

Nylock nuts have no sealing properties. The nylon part is not designed to seal, and does not seal. Sealing nuts look different. With sealing nuts, the sealing material is on the inside of the nut, rather than the outside. I understand folks who think these nuts are leaking, but I am not convinced. In order to leak, oil still has to get past the gasket under the valve cover. My suspicion is that oil is getting out of the engine somewhere, and blowing onto the nuts. It is very windy down there, and most of the wind is blowing down through the engine, where leaks are located. Particularly the heads, where rocker shafts and oil return tubes can leak.

So what did you find?
 

Hi JK911,

I would be interested to see if your problem had been positively identified.

I have similar situation on my 74 2.7. The head studs torque without a problem. I even backed them off and retightended to make sure the torque was correct. This is the third time I have checked the torque and this last time I increased to 27ft./lbs. which I don't think was a good idea. Anyway, I put everything back together, adjusted valve, etc. Started it up, and Phat, Phat, Phat,... from #2 and #6.

So..., I performed a rudimentary leak down test by hooking my compressor to cylinder #2. Sure enough, there was a distinct leak between the cylinder and the head. I could not hear any air pass through the exhaust, intake or crankcase. Thus, it would appear that I have a burnt head gasket on #2 (and possibly #6 I did not check).

I hope yours is just an exhaust leak. Looks like I am headed for a rebuild or upgrade regardless.

Jason 74 911

Are you guys sure it's not an exhaust leak at the manifold? I had the same sound (when it first started it sounded like a loose valve) then it got worse. Turns out the 3 into 1's (PO ditched the thermal reactors) was loose. I mean, I could have probably turned the nuts by hand. So, I put all new gaskets and nuts on and it was perfect!

A few thoughts.

You seem to be worried about what could be the problem. Like me, you seem to be at a disadvantage since you have only your car to judge what is "normal".

If it was me, I would take it to my trusted professional wrench, and ask his opinion. He has seen many, many Porsches in various states of repair and can be a better judge as to what is a disaster in the making and what is within the realm of normal sounds.

Also, if you know you have a hole in your muffler or exhaust, as a temporary patch, you may want to install a "muffler bandage" to seal the hole. This will help you tell if the sound is from your muffler or exhaust or somewhere else.

I hate to resurrect a long dead post, but what was the "final verdict" here? Thanks!

Hi Art. Well, I haven't done anything yet. I will be pulling the motor shortly replace the cam chains and fix some oil leaks. All the head studs remail torqued but there is a definite compression leak on at least a couple of cylinders. I can hear a Phat Phat phat when it is warm. However, I haven't been able to positivley ID the source. Another issue my engine had is that the previous PO had installed mechanical tensioners on the timing chains. As a result of heat expansion and unknown miles the left side chain is slightly loose when cold even when the tensioner is exapanded 100%. Once it warms it actually tightens up. Therefore, it is possible that the cams moved, due to the chain slack, allowing for the compression loss. Oddly, the engine is running very well.

Jason,

Thanks for the update, sounds very familiar, except my problem are the head studs. The engine runs great with minimal oil leaks, but when the engine is warmed and I step on the gas, I hear the "phat phat phat" ominous sound I have been dreading. I'm going to drop the engine this fall after our home addition work is done. I'm going to buy Wayne's book and figure out a plan based upon what I find out. Good luck!

I'm with Superman on this... The stud are not where the leak is occuring, it is either the seal/gasket leaking and the oil droppng to the lowest point, or it's return tubes doing the same thing. The nylock isn't a sealing nut... The torque is what is supposed to seal the cover...