Hi,
You can pressure test the system with an automotive cooling system
pressure tester. The exhaust elbow/reservoir, exhaust manifold, heat
exchanger, and intake manifold can be tested for leaks by moving hoses
around and or plugging them. Check the reservoir first because I suspect it
has rotted thru to the exhaust cavity.
Jim In MA
"Olaf-C. Lepthien" wrote in message
om...
Hi,
pls excuse my bad english because i`m from Hamburg, Germany.
I bought an old Formula One equipped with Merc. 470 Engine. During
test drive on an river with the owner engine start was fine, it went
41 knts for a while. Total test ride was about half an hour without
problems or overheating.

After transport to my home i did some test driving in salt water, but
only short trips without problems. After that on my first longer trip
i went 25 minutes with 22 knts at about 2300 rpm, stopped for two
hours and then started to drive back. After 5 minutes at 2300 rpm
engine sound changed, drove slower about 1500 rpm suddenly felt engine
loosing power, then stopped at idle but engine shut off immediately.
Temperature on instrument was not showing anything special but engine
was extreme hot, smoking and melting the spark plug cables.
After engine cool down i checked oil (was black and no sign of water)
and water in internal circuit which was gone !!!. Checked impeller,
was fine. At home equipped with new spark plug cables and plugs i
filled up water and tried to start the engine whithout success. I
checke again the manifold water reservoir and the water was gone again
and there was a smell of gasonline. People told me i had to repair the
cylinder head gasket because of the temperature destroying it.
So i changed cyl head gasket, intake manifold gasket, exhaust manifold
gasket and let the head be plained. The surface inside the combustion
chamber was a bit rusty especially in cyl 1 and 3.
After assembling filled up water and checked compression of cold
engine which was about 6 bar on all cyls. I cranked the engine and it
started working, shut off at idle rpm some times but then worked fine
at idle rpm with flushing device. After engine running about 20
minutes checked water and a little bit was gone again.
I decided to have a test drive after installing a new thermostat
instrument (not the thermostat). On test drive went at about 2200 rpm
for 15 minutes. Everything seemed fine, engine wasn`t running hot but
shut off at idle rpm after stopping, was able to start engine again
easily. Checked water in circuit, some water was gone, filled up much
less than a quart (~ 1liter)again. After 15 minutes more at 2000-2500
rpm engine lost power, i stopped engine immediately. Checking oil now
i found water in oil (grey), water in circuit was gone almost
completely, reservoir smelled like exhaust smoke.

I didn`t make an compression test untill today, cleaned the motor from
oil/water mixture yesterday. I remember that the amount of oil was a
little more than usual so somebody said that after the first drive
with defects there could have been water in the oil which wasn`t
emulgated and my mistake was not to change oil ?

Do i have a cracked exhaust manifold / elbow ? I understand that this
is the reason why the inner circuit is loosing water and old cyl head
gasket was rusty. I don`t believe that i have a cracked cylinder wall
because engine was running great during last test drive before the
problems came again. But of course i don`t want to buy exhaust
manifold/elbow without exactly knowing where the problem ist located.
Does somebody have an idea or is there a possibility to test the
exhaust manifold ?

I know the preowner knows about the problem but doesn`t tell me ...

best regards
Olaf-Christian