chuck <chuck@localhost.localdomain> wrote in
news:slrndld8l1.6us.chuck@localhost.localdomain:

> On 2005-10-19, TeGGeR® <tegger@tegger.c0m> wrote:
>> chuck <chuck@localhost.localdomain> wrote in
>> news:slrndlcato.6ma.chuck@localhost.localdomain:
>>
>>>
>>> My 91 Civic presurrizes the cooling system upon startup. The
>>> overflow tank is also under pressure and there is a slight leak
>>> under the cap. There was also a spare cap under the hood when I
>>> bought the thing not long ago. Is this pressure normal or is the
>>> head gasket going? There is no oil in coolant, no coolant in the
>>> oil, and it doesn't smoke. It runs good and doesn't overheat. But if
>>> you start it with the cap off it sprays coolant. Should the overflow
>>> tank be vented? I only see one hose. THanks in advance.
>>
>>
>>
>> Something is seriously wrong here. Are you saying the expansion tank
>> has a pressure cap on it?
>>
>
> Well, it has a screw on type cap with the single hose from the
> radiator attached to it.



That's normal.



>
>> On your car there should be an 0.9-bar cap (13lb) on the radiator.
>> This cap should allow pressure to bleed off into a tube in the rad
>> filler nack that goes to a non-pressurized expansion tank.
>
> The cap is a 13 lb. I can't see how the expansion tank can be
> non-pressurized though. There's only the single hose going to it, and
> it screws onto the expansion tank unlike most snap on type ones that
> I'm accustomed to seeing. I see no apparent way for the tank to vent.
> The expansion tank is original...it slides right onto the motor mount
> bracket. Nevermind about the expansion tank...I found a hole drilled
> into a flat spot of the threads.


The tank /has/ to vent. As your coolant heats up, it expands. As it expands
it pushes into the reservoir, so the reservoir level will rise. When you
shut down and the car cools off, the reservoir level will go back down
again as coolant is sucked back into the rad.



>
>>
>> Is the rad cap aftermarket or OEM?
>>
>
> It's an aftermarket. Does this *really* matter?



Yes. If the cap is the wrong design for the car, or is defective, this will
affect cooling system operation. Change it just in case. It's cheap enough.



> I'm thinking about a
> thermostat, but it doesn't overheat and it does warm up as it should.


If it doesn't overheat, then the thermostat is fine.


>
> What I'm thinking of doing is screwing my compression testing onto
> each cylinder and attaching to the air compressor and looking for
> bubbles in the coolant. I guess that would tell me if it is a head
> gasket.


Sure would. But if you're not losing coolant, then your head gasket is
certainly fine.


Other than your report of "spraying", it doesn't sound as if there's
anything wrong with your car.




--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/