Question of cooling system design theory,I-5 engine

[Cody Forbes]

I don't have anything too useful to add other than a note that GM made a 4-way heater valve in the mid 90's used on the LT1/LT4 and LQ (truck) equipped vehicles. Picture four hose fittings and a 2 way valve (forget if it's cable or electric). In position one the coolant flow was routed through the heater core and the bypass blocked. In position 2 the bypass is opened and the heater flow is completely blocked off. Would be an elegant solution to impliment.

-Cody (mobile)

On Apr 12, 2011, at 1:20 PM, Andrew Dickinson <amdickinson at rogers.com> wrote:

> Hi Tony:
> 
> I have experienced similar issues on the 5k/2c cars.  I have thought of 
> installing a set of valves to (A) Isolate the heater core, and (B) connect a 
> by-pass when the core is shut off.
> 
> I have also pondered the constant flow.  I can't see a German engineer allowing 
> hot to flow when it should not UNLESS the idea is to keep some small amount 
> flowing to prevent corrosion.  I discounted that idea and actually plan to 
> install the multi-valve set up.  I have even thought of ddraining the core 
> during summer months but I am not sure that would be more or less beneficial.
> 
> That's my $0.02.
> 
> cheers;
> 
> Andrew
> 
> 
> 
> ________________________________
> From: Tony Hoffman <auditony at gmail.com>
> To: quattro at audifans.com
> Sent: Tue, April 12, 2011 1:02:26 PM
> Subject: Question of cooling system design theory,I-5 engine
> 
> Fellow Q-heads,
> 
> I have a question of theory as I'm working on the A/C system of my '86 4000
> Quattro.
> 
> Firts, a little background. I live in Houston, where we already are seeing
> 90 degree highs :( So, since my A/C compressor dies at the end of last
> summer, I've decided to upgrade while I'm in there. I have installed the
> rotary compressor from a 90Q, which also requires the lines, brackets, and
> Oil filter adapter. All said and done, the system is putting out 44 degrees
> from the vents at 80 degree outside temps. Pretty good, for what I've seen
> so far. I've never been able to get it below 40 with the old setup. If I had
> the old setup just as it is now(I'll go over those details in a minute) it
> would be putting out somewhere around 52-55 degrees. So, I'm pretty pleased.
> 
> However, in every 4000Q I've owned or driven recently, even with the heater
> all the way off (verified under the hood against the stop) the heater never
> quits giving out slightly heated air. I've replaced the heater valve on
> several of them as well. This current one will be replaced, as I have a new
> one here, but hasn't yet.
> 
> Looking at the coolant routing, it appears that the heater core runs are
> sort of a "bypass" of sorts for the thremostat. So, if that's the case,
> maybe it isn't designed to ever shut off completely?
> 
> So, here's the question, if I completely shut off that coolant flow, does
> that create hot spots in the cooling system or engine. I really can't see
> how it could, but I want to make sure.
> 
> With the old system, I did have a set of pinch pliers designed to stop flow
> through rubber lines when you are working on them. Examples would be when
> you take a fuel hose off the pump, but don't want to drain the tank. I did
> that all last year, as that was the only way to get the temp from the vents
> below about 55degrees on hot days. I did not experience any sort of
> overheating, nor was anything damaged that I know of. But, I've got a valve
> setup that I'll be adding to permenantly shut off the heat during the
> summers, and I just want to make sure I'm not going to stop the flow that
> may be engineered into the cooling system.
> 
> As always, TIA,
> Tony Hoffman
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