Coolant Leak Won't Stop...

Might seem like an obvious question but is the pipe still round or has it been knocked and now oval ? You might not get a good seal if it is too far off round.
You mention the more you tighten the clamp the more it leaks, might tie up with being oval, but sounds like hose id is too big to me
If the pipe has those raised bits near the end, be sure you site the hose clip well away from it on the plain section

 

We all hope it works out for you but your diagnostics aren't convincing, doesn't mean that you aren't correct mind you. ;-)

 

This issue in all its particulars appears more and more mysterious to me.

Best
Martin

 

Coolant system being over-pressurized somehow by a small combustion chamber leak??

 

No.

 

and why is it you know this is not the case?

 

A minor scuff or ding to the inside of a cylinder wall is enough to allow the oil that lubricates the piston rings to sneak by and burn up during combustion, which can cause black smoke and/or a loss of compression. Unless you injured the head gasket, then damage to the combustion chamber almost always would lead to oil leakage. The geometry of the 308 engine block and its coolant passages/cavities is such that it would require a catastrophic puncture of the cylinder wall (like, say, throwing a rod) to allow coolant to flow into the combustion chamber or - conversely - for combustion waste gasses to gain access to the coolant system. Any such catastrophic cylinder failure will blow your motor long before a weeping coolant hiss arises as your most noticeable issue. HOWEVER, playing your theory, IF such a severe rupture occurred, coolant from the pressurized system likely would flow INTO the combustion chamber, as the exhaust valves would still be working and allow the pressure to be relived through the headers, where you would see a bunch of white smoke from burning coolant. At any time the motor is running (assuming you've properly bled air from the system - which is still on my recommend checklist items), the coolant system is highly pressurized already; if the combustion cycle were dumping into the coolant system somehow and over-pressurizing it, you'd see a ton of overflow coming out of the expansion tank drain hose, and not a small weeping leak. But mainly, without a catastrophic gasket or cylinder wall failure, it would be near impossible to observe the scenario you posit, and the owner hasn't described any other symptoms to suggest those failures.

IN SHORT: The coolant system doesn't have direct access to the combustion chamber in a manner that would explain it becoming pressurized by combustion, except in an event that would have caused catastrophic engine failure.

 

If you think it might have a crack then wipe it clean and rub some school board chalk over it. The chalk will show in the crack if you have a good contrasting colour

 

"Unless you injured the head gasket"

I assumed this is what they meant as the other scenarios you describe would presuppose they have extremely poor knowledge. I would give them the benefit of the doubt. I try to choose my words carefully online as advice may come across as criticism (this is very much the former )

I have seen several engines blow past bad head gaskets or through cracked heads to pressurize the coolant system. It is a valid possibility and not one I'd thought of (or anyone had suggested yet.)

 

Wasn't this 308 running a turbo set up the previous owner installed? Or was it just his Testarossa running TwinTurbo's.
By chance, was a leakdown and compression test performed at time of purchase? Would at least take this theory off the board.
Seriously hope it's just a simple problem with coolant hose/fittings..

 

Thorn, if you haven't got a stethoscope, use a piece of small tubing plugged into your ear and locate the origin of the hiss. You might be squirting out of the head gasket onto that pipe. A bit of ceramic engine seal and a head re-torque may cure the problem if that is the case.

 

While diagnosing with just pressurized air and suspect this area, a leak detection spray for pressurized air lines and fittings would also help a lot.
Amply sprayed onto suspected areas it creates big bubbles at the leaking spot after pressurized air is applied.
I use it permanently to find leaking air lines or fittings in my compressed air supply.
And it creates no mess. It simply dries without any residue.
I suspect it's nothing other than something similar to highly concentrated soap water. But it's handy to have it in a spray can.

Best Regards
Martin

 

Per what Martin said, I have always just used soap (Dawn)/water in a spray bottle and spray it onto the suspected areas. I use the same bottle of soap/water for natural gas plumbing, air compressor fittings, suspected tire leaks, etc. I also use it to wash motorcycles!

 

You make any progress on this?

 

Well, it was never a bad idea to replace the rubber hoses, so - best case - you paid for an unnecessary pipe (maybe they'll take it back for a re-stocking fee just to trim your outlay). If the replacement isn't made of aluminum when it arrives, I'd consider re-using the original. Feel better soon.

 

Trust me, some of us giving advice here are paying off huge "debts" for prior community support during the early days

I think that clamp corrodes due to dissimilar metal contact. It's basically identical to the air of intake hose clamp for a carb car that costs $2 some places and $40 elsewhere. I'd trim it down about 6" first or you'll just be coiling up some extra length at the end. I believe it's there to stabilize the long tubes and keep them from shearing against the hard steel chassis tube that they run through because of bumps or vibration. A little trick is, get a strip of insulation foam and wrap it between the bundle of pipes and the clamp to eliminate metal contact and hopefully reduce future corrosion.

 

The part number for the clamp is 10300190. I remember having to try T. Rutland's, Ricambi, Ferrparts, and GT in Arizona, and the prices were all over the place. You should be able to get one for less than $5 (although I'd recommend buying two, because it's easy to mangle one if you haven't wound one up before - or maybe if you're just a klutz like me).

Here's a pic of what I did to put some insulation between the metals...
Image Unavailable, Please Login
Image Unavailable, Please Login

 

So, did I miss something? Where was it leaking?

 

Sounds like it was leaking where he thought the original pipe was leaking, and new hoses fixed it. He also found a corroded clamp under the car where he drained the system.

 

Since originality is not so important for me in such obscure places, I used a wide cable tie.
Convenient, no corrosion questions, works and holds up since 20 years.

I do not think, like you mentioned, that dissimilar metal contact causes that corrosion, since according to the electromotive chain, zinc and steel are the more noble metals,and in a galvanic cell with these, aluminium would sacrifice itself.

Best Regards
Martin

 

The bands are available at Belmetric.

 

I think there's a special tool that you can get for those types of clamp. I reckon the idea of clamping the pipes together is to stop them rattling, so a tie-wrap seems like a pragmatic solution if you don't have a new clamp to hand.

Well done on solving the problem and hopefully you'll now get to enjoy the car for a while.