Quick and dirty check method for blown head gasket...
With engine cold [be safe] remove radiator cap.
Start and run the engine to operating temperature, while observing what
happens to the coolant at the radiator fill neck.
As temperature comes up and engine runs, if the head gasket is blown, you
will see the coolant surge at the filler neck.
If you accelerate the engine to fast idle... coolant will surge and
overflow... more engine speed will increase the size of the surge.
What is happening with a blown head gasket is that cylinder pressures are
much higher than coolant pressures... ie.. 15 lb radiator cap thus,
combustion gasses are inserted into the coolant system, which overpowers
the "closed system" and pushes coolant out the overflow...
Generally, combustion gas, being much hotter than the cooling system can
shed heat, will cause coolant overheating...
Depending on how "blown the gasket is" ... you usually see coolant loss..
as the gasket degrades further [and it will] more hot combustion gases are
inserted into the coolant and you see a rise in engine temperature at
first, not much, as gasket degrades.. more heat.. until you are well into
the death sequence where coolant is pushed out, thus less coolant, and hot
gasses are pushed in, thus more heat to shed, with less coolant.. until the
engine cooks and seizes..
As you lose coolant, most systems mount the temp gage sending unit high in
the system [ie heat rises] ... as coolant is blown out that sensor may
be left bare of coolant and actually read colder, all while the engine is
committing suicide...
If you don't see a surge at the filler neck, and find no leak points, there
is a cap you can rent at FLAPS with a pressure gage to read coolant
pressure... [Snapon will sell you a set for several hundred dollars, rent
one]
There is a weep hole at the bottom of the water pump... hidden behind the
fan drive pulley... look for it.. if you see any moisture, water pump seal
has failed and you will lose coolant from that.. so worth checking.
Obviously... look for leaks at hose clamps, heater hoses, etc.. look at the
engine block for freeze plug leaks [they get rust holes sometimes and weep.
as engine temp rises.. they weep harder.]
Hope any of this helps. Good luck.
On Wed, Oct 7, 2020 at 9:12 PM Allan Streib via Mercedes <
mercedes@okiebenz.com> wrote:
> If it's using coolant that rapidly I would think that you would see one
> or more of the following if it's due to a head gasket leak:
>
> - white smoke in the exhaust, and/or smell of ethylene glycol
> - coolant in the oil (milky appearance)
> - oil in the coolant
>
> Allan
>
> Craig via Mercedes writes:
>
> > The tires on the BRV were getting rather worn, so I got a new set of
> > tires. I then noticed the very slow coolant leak increased dramatically,
> > requiring me to fill the radiator every time we left the house.
> >
> > I'm thinking it may have blown a head gasket, but in calling our local
> > O'Reilly the fellow who I spoke with (after 1700) said they had nothing
> > to check coolant for combustion gases. I'm thinking I should call again
> > tomorrow morning, and maybe call the local NAPA as well.
> >
> > Any suggestions or comments?
> >
> >
> > Craig
> >
>
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