On 2005-10-20, TeGGeR® <tegger@tegger.c0m> wrote:
> 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.

I'm curious what effect a thermostat with the air bleed valve pointed
downward would have on a system.

This car also has hot/warm intermittant start issues and I'm wondering
if these could be related to air (that I can't seem to get rid of)
hitting the ECU temp semsor.

It doesn't lose coolant and doesn't pressurize the expansion tank when
running, but when cranking the engine and only when cranking the
warm/hot engine, I hear air escaping from the vent hole in expansion
tank. THe thing runs great except for the intermittant start issues.

BTW, I've already resoldered the main relay and can hear the fuel pump
at 'key on'.

The next no start I guess I need to check for spark.

I do get an Oxygen sensor code. From what I've read this wouldn't keep
it from starting...would it?
escaping from the vent in the