X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-d22.mx.aol.com ([205.188.144.208] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2364938 for flyrotary@lancaironline.net; Tue, 02 Oct 2007 17:57:37 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.144.208; envelope-from=Lehanover@aol.com Received: from Lehanover@aol.com by imo-d22.mx.aol.com (mail_out_v38_r9.3.) id q.c98.1d1be348 (29672) for ; Tue, 2 Oct 2007 17:56:58 -0400 (EDT) From: Lehanover@aol.com Message-ID: Date: Tue, 2 Oct 2007 17:56:58 EDT Subject: Re: [FlyRotary] Coolant Water Pressure To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1191362218" X-Mailer: 9.0 Security Edition for Windows sub 5378 X-Spam-Flag: NO -------------------------------1191362218 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 10/2/2007 12:40:31 P.M. Eastern Daylight Time, bbradburry@bellsouth.net writes: Can someone enlighten me a little on the science of this pressure? It seems to me that there could be some pressure build up on the positive side of the pump, but it would go negative on the suction side, so the net effect of the pump should be close to zero?? The volume in the system expands with heating and hydraulic locks against the cap. Some is forced past the cap at that pressure. A rather small lowering of coolant temp, such as reduced power, drops the pressure quickly, and in an amount that seems alarming. This is because the system has a small total volume. So the system looses a bit of volume, and the pressure drops to zero. Since there is no cushion or accumulator feature. So, it reacts suddenly to small temp changes. Many modern car systems have a recovery bottle with a cap that seals tight with no relief feature at all. A specified air volume is left above the coolant level in the bottle, (fill to level line) and expansion produces a linier increase in pressure, without exotic changes in pressure, with small temp changes, but always on the positive side (always has pressure when heated). The other advantage is that with the hose in the bottom of the bottle, only liquid can return to the engine during pressure changes. This soon removes all of the unwanted air from the system after a few heat cycles. This was the stock Mazda system from the 70s. Measuring pressure right after the pump just shows dynamic changes based on pump speed and temperature. And dynamic pressure may be higher than the cap setting, and dump coolant without regard to temperature. Pressure between the pump and the radiator will be the highest. Pressure just on the intake side of the pump will be the lowest. I use the early Mazda system with a bottom fed bottle and a 22 pound cap on that. The bottle is kept about 1/3 full of coolant. Never a cooling problem on even the hottest days. Lynn E. Hanover ************************************** See what's new at http://www.aol.com -------------------------------1191362218 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

In a message dated 10/2/2007 12:40:31 P.M. Eastern Daylight Time,=20 bbradburry@bellsouth.net writes:

<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>

Can someone enlighten me a l= ittle=20 on the science of this pressure? It seems to me that there could be=20= some=20 pressure build up on the positive side of the pump, but it would go negati= ve=20 on the suction side, so the net effect of the pump should be close to=20 zero??

The volume in the system expands with heating and hydraulic locks=20 against the cap. Some is forced past the cap at that pressure. A rather= =20 small lowering of coolant temp, such as reduced power, drops the pressure=20 quickly, and in an amount that seems alarming. This is because the system ha= s a=20 small total volume. So the system looses a bit of volume, and the pressure d= rops=20 to zero. Since there is no cushion or accumulator feature.

So, it reacts suddenly to small temp changes.

Many modern car systems have a recovery bottle with a cap that seals ti= ght=20 with no relief feature at all.

A specified air volume is left above the coolant level in the bot= tle,=20 (fill to level line) and expansion produces a linier increase in pressure,=20 without exotic changes in pressure, with small temp changes, but always on t= he=20 positive side (always has pressure when heated).

The other advantage is that with the hose in the bottom of the bottle,=20= only=20 liquid can return to the engine during pressure changes. This soon removes a= ll=20 of the unwanted air from the system after a few heat cycles.

This was the stock Mazda system from the 70s.

Measuring pressure right after the pump just shows dynamic changes base= d on=20 pump speed and temperature. And dynamic pressure may be higher than the cap=20 setting, and dump coolant without regard to temperature. Pressure between th= e=20 pump and the radiator will be the highest. Pressure just on the intake side=20= of=20 the pump will be the lowest.

I use the early Mazda system with a bottom fed bottle and a 22 pound ca= p on=20 that. The bottle is kept about 1/3 full of coolant. Never a cooling pro= blem=20 on even the hottest days.

Lynn E. Hanover

See w= hat's new at AOL.c= om and Make AOL Your Homepage.

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