Pressure Used to Test Cooling System?

I own a '93 Chevy K1500 pickup with a 5.7L engine. Recently I had the
intake manifold gasket replaced to stop an oil leak. 3 or 4 days after
the work was done I found there was no coolant in the overflow
reservoir but the radiator was still full, I guessed there may have
been air trapped in the system. I called the shop and they wanted to
do a pressure test to be sure there were no leaks. After the test was
done no leaks were found and the mechanic told me that he had pressure
tested the cooling system to 18 psi. This is 3 psi. higher than the
radiator cap and now, 250 miles later, I can smell antifreeze outside
the truck after the engine has warmed up. I can't see a source or hear
a leak but from looking underneath the truck I can see a few drops of
coolant that have collected at the back end of the block, between it
and the torque converter cover. There is no sign of oil in the coolant
or vice versa. Is 18 psi too high a pressure to use to test the
cooling system and if so, could it have unseated a freeze plug on the
back of the engine block? Does it seem more reasonable that the new
intake manifold gasket is leaking?

In article .com>,
gunny > wrote:
>I own a '93 Chevy K1500 pickup with a 5.7L engine. Recently I had the
>intake manifold gasket replaced to stop an oil leak. 3 or 4 days after
>the work was done I found there was no coolant in the overflow
>reservoir but the radiator was still full, I guessed there may have
>been air trapped in the system. I called the shop and they wanted to
>do a pressure test to be sure there were no leaks. After the test was
>done no leaks were found and the mechanic told me that he had pressure
>tested the cooling system to 18 psi. This is 3 psi. higher than the
>radiator cap and now, 250 miles later, I can smell antifreeze outside
>the truck after the engine has warmed up. I can't see a source or hear
>a leak but from looking underneath the truck I can see a few drops of
>coolant that have collected at the back end of the block, between it
>and the torque converter cover. There is no sign of oil in the coolant
>or vice versa. Is 18 psi too high a pressure to use to test the
>cooling system and if so, could it have unseated a freeze plug on the
>back of the engine block? Does it seem more reasonable that the new
>intake manifold gasket is leaking?

18psi is perfectly reasonable for a pressure test.

However, you COULD have lost a freeze plug or have a cracked hose, even.

If the new gasket was installed properly, it shouldn't be leaking, but
you don't know it was installed properly until you find the source of
the leak. An ultraviolet light should pinpoint it very quickly. You
may need to wash the engine down, then drive it a bit before using the
light, especially if there is a lot of old coolant residue from before.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
> In article .com>,
> gunny > wrote:
>> I own a '93 Chevy K1500 pickup with a 5.7L engine. Recently I had the
>> intake manifold gasket replaced to stop an oil leak. 3 or 4 days after
>> the work was done I found there was no coolant in the overflow
>> reservoir but the radiator was still full, I guessed there may have
>> been air trapped in the system. I called the shop and they wanted to
>> do a pressure test to be sure there were no leaks. After the test was
>> done no leaks were found and the mechanic told me that he had pressure
>> tested the cooling system to 18 psi. This is 3 psi. higher than the
>> radiator cap and now, 250 miles later, I can smell antifreeze outside
>> the truck after the engine has warmed up. I can't see a source or hear
>> a leak but from looking underneath the truck I can see a few drops of
>> coolant that have collected at the back end of the block, between it
>> and the torque converter cover. There is no sign of oil in the coolant
>> or vice versa. Is 18 psi too high a pressure to use to test the
>> cooling system and if so, could it have unseated a freeze plug on the
>> back of the engine block? Does it seem more reasonable that the new
>> intake manifold gasket is leaking?
>
> 18psi is perfectly reasonable for a pressure test.
>
> However, you COULD have lost a freeze plug or have a cracked hose, even.
>
> If the new gasket was installed properly, it shouldn't be leaking, but
> you don't know it was installed properly until you find the source of
> the leak. An ultraviolet light should pinpoint it very quickly. You
> may need to wash the engine down, then drive it a bit before using the
> light, especially if there is a lot of old coolant residue from before.
> --scott
I'm not sure if a 93 has the same coolant setup as my 90 K1500, but
there's a hardline that I think goes from the TB to the intake or
somewhere (the truck's at home) and on mine it's starting to seep. My
90 Beretta has the same kind of hardlines and after 17 years they're
starting to corrode in spots and have had to replace some of them.

I don't think 18psi is excessive, but any time you stress something you
run the risk of causing further leaks. It's like probing a rusty
exhaust with a screwdriver....

The previous owner of my truck already replaced the rad cap with a 7psi
one because it had multiple small coolant leaks....

Ray