wrote:
> i have a 1990, 300m with a very slight leak somewhere from the cooling
> system evidenced by a slow dripping of antifreeze from the botton of
> the radiator. i have pressure tested it and found no drop in pressure.
> when i run the motor with the pressure guage attatched the pressure
> rises very steadily - no spurts or jumps, and gets up to the "danger"
> mark on my pressure guage. it has a 16 psi cap. what is the operating
> pressure for the cooling system supposed to be? any ideas. ps. it was
> 90 degrees when i tested it. thanks. brian
>

Are you actually loosing coolant - i.e., are you having to add any
periodically? One reason I ask is that the LH cars *routinely* develop
leaks in the plumbing going to the tranny fluid coolers (one built into
the radiator, the other a separate coil mounted in front of the
radiator) and engine oil cooler (passenger side of radiator). (Also
there is a p.s. fluid cooling coil in front of the radiator.) The
location of the leaks (at rubber hose-to-metal lines with screw-type
hose clamps) is such that it would appear to be coming from the radiator.

If it is in fact engine coolant leaking, the two most likely sources are
radiator hose (hole or loose clamp) or one of the plastic tranny tanks
has a leak (not uncommon based on my read of LH car forums).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')