On Wed, 08 Dec 2004 08:18:03 GMT, Paul Halliday wrote:
I got a good look at it in mid-steam yesterday, since I was lucky enough to be
parking after a short trip just as it started. Steam seemed to be coming from
all over the radiator, particularly the top half of the radiator. Not
especially from near either the top or bottom hose. Ah well, I really should
flush the system sometime in the next few months, so maybe I'll take advantage
of that opportunity to replace the radiator anyway.

In any event, I have a more pressing issue now: it sounds like I just rusted
myself a hole somewhere in the exhaust plumbing. One practically requires ear
protection to drive the car now. Not sure if the leak is at the exhaust
manifold, or down towards the catalytic converter. Any pointers on how to
pinpoint it? If it's something I can reach in the engine compartment I might
try to fix it myself, otherwise I'll probably give it to a mechanic.

Thanks,

John

On Fri, 10 Dec 2004 20:41:23 GMT, John B <rotten_NOSPAM_ (AT) ccil (DOT) org> wrote:
Well, if there's a pinhole leak, the flush may very well expose that leak
into a more pronounced hole, so yeah.

An exhaust manifold crack (between #2 and #3, almost always) is more of a
hiss than a roar. If you have a roar, I'd suspect the header pipe, probably
where the support that goes off to the back of the transmission is welded to
it. Ahem, just a guess.

Exhaust work would be a snap if not for rust. It's one of the few things
I won't do on my cars, and I do nearly everything else. I especially
dislike rust falling into my eyes while I'm working on stuff, safety glasses
or no.

Dave Hinz

The exhaust leak turned out to be easy to find, as it was a giant crack in the
intermediate pipe (between the catalytic converter and the mid muffler), just
aft of the collar where it bolts to the catalytic converter. I undertook to
replace it myself, which was successful though a pain in the ass: the bolts
holding the old collar to the catalytic converter were rusted beyond hope and
had to be sawed off; and the intermediate pipe was separated from the mid
muffler only after extensive heating with a blowtorch and much swearing.

And regarding the steam at the radiator, I dumped some Prestone brand radiator
leak stopper into the system-- only time will tell whether that helps anything.


John

"John B" <rotten_NOSPAM_ (AT) ccil (DOT) org> wrote

I read the threads on the steam thing recently and didn't have time to
reply.

For what its worth, on my C900 I came to the conclusion that it was
condensation on the engine block, built up overnight. Because:-
1/ I only noticed this in cold weather, when dew was likely.

2/ There was sufficient steam to indicate a leak, but no leak could be found

3/ The water level simply refused to drop a millimetre in a year of
motoring.

I don't like water or oil additives, if you really have a leak, you need to
fix the leak not fill the system with crud! (does anyone else remember the
Mike Harding sketch and the eggs in the radiator?!)

Cheers

Al

Al wrote:
My take on a likely source of this mysterious steam: (and I do remember
this as a regular "feature" on my 1990 900)

When the engine cools and the fluid in the closed cooling system
contracts it draws coolant from the overflow tank which creates a small
vacuum in the tank. If I'm not mistaken, there is a poppet valve in the
pressure cap that allows this vacuum to be relieved by drawing in
outside air.

When you next run the car and the heated coolant expands it can
eventually exceed the pressure rating on the cap (12-15 psi?) and
release some of the air from the reservoir. This could be the source of
the steam.

If this is the source, it should be easy enough to see if one were to
watch it through an entire warm up cycle. But then again, I suppose
this would fall into the "watched pot" category. It probably would not
happen just because you were expecting it to...

-Fred W

We certainly have a lot of potential explanations for the steam.

I find Al's explanation to be quite creative, and I would believe it if not for
the fact that I've driven the car for the last 10 years, and yet hadn't noticed
the steam until this fall. Although I will grant that I'm probably more
paranoid about my car than I used to be, so perhaps I'm just being more
observant. Does anyone care to comment on whether they remember 900s doing this
when they were new?

Fred's idea is equally creative, but I have observed the steam coming from the
radiator itself, not the expansion tank.


John