Yet another taurus heater core problem

My Dad's 99 Taurus seems to have been having the same clogged heater core problems that have been reported by numerous posters here. He had the system
flushed by his regular mechanic at the start of last winter, which helped somewhat but did not return the heat to full operation. With the onset of cold weather in November, it was obvious that the heater performance had declined again, so he had his mechanic do another flush, this time with a special "high pressure" flush system the garage had just gotten. The heater performance remains very poor. I discussed the problem with the mechanic, who mentioned that the heater core had a bypass tube, which, if clamped shut, improved the heater performance. He was a little confused because he had apparently never seen a bypass straight across the heater core like this.
From what I have read of others comments here, it seems that the problem is relatively easily solved by doing a thorough backflush, and that the poor results other posters (and my dad as well, probably) have got from having mechanics do the flush is that they don't seem to persist until the core is completely cleared (which may take 3-4 flushes). My questions are:
1) From some posts, I get the impression that the bypass was put on the heater core as part of a recall fix. Can anyone tell me the problem that was being fixed, and why/how the bypass fixes it?
2) Since the heater performace improves substantially with the bypass clamped shut, is there any damage likely to be created by just leaving it clamped shut until I can get around to doing a thorough backflush? (Morning temps are less than 10 F the last few days...)
thanks in advance,
Paul
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Paul W" wrote

Assuming we're talking about the 3.0 pushrod engine, here's the TSB that includes the bypass hose: http://blizzard.zmm.com/waterpump/BrownCoolant.pdf
As you can see, there's no real explanation of what the hose does. I've heard a couple of different guesses as to the purpose of the bypass hose, but none that made much sense. I can assure you, though, that with the hose in place, as long as everything else is working, you'll have plenty of heat.
There are really only two likely causes of low heat on these cars: either the core is blocked or the water pump is weak. (Of course it could be both) Since you've had the core flushed and it didn't help, the pump becomes the next logical suspect. The water pumps on these cars have an unusual failure mode in that the pump's impellor degrades very badly, but typically the engine temperature is seemingly unaffected. I wouldn't be at all surprized if a perfectly competent mechanic who hasn't seen this problem before tells you that it can't be the water pump. I wouldn't have believed it if I hadn't seen it for myself: http://blizzard.zmm.com/waterpump/
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Wow....
That's scary...
--

(\_ _/)
(='.'=) This is Bunny. Copy and paste bunny into your
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

old pump impeller was essentially a disc. I replaced the pump because the seal was gone and I had drip warning.
Jimbo
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sniiped stuff

The problem was poor flow balance and/or low total flow through the block at closed and small stat openings. The bypass was added and the pump impeller was redesigned to improve the balance and a few other characteristics. A 3 mm restrictor was added in the degas line to reduce coolant aeration in the system.
If I recall correctly pre '96 systems had a bypass but no degas bottle, but don't hold me to that. Can't say if your vehicle has the new impeller style. Hard to tell if you would have any problems by clamping off the bypass...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Rick" wrote

Wouldn't low flow be normal when the thermostat is fully or partially closed?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Generally lower than fully open, yes. However, there is a minimum flow needed for safe operation at various engine conditions.....
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Rick" wrote

The brown coolant TSB mentions "bank to bank coolant flow imbalance" as one of the possible causes. I've never really understood exactly what that means. "Bank" to me would mean one side of the V, as in the front set of three cylinders is getting more or less coolant flow than the rear set. But then how the bypass hose in the heater line might affect that seems a little voodooish.
At any rate, Paul shouldn't have to restrict the bypass hose to get heat. There's something wrong in his cooling system. (My money's on the water pump.) My bypass and a whole lot of others are unrestricted and our heaters work fine.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That's correct, but it's normally called left and right (as viewed from the rear of the engine)
No voodoo involved at all...

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Rick" wrote

How does the heater bypass even up the imbalance, then?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If it had worked in every case, they wouldn't have introduced the new impeller design part of the fix.
If you look at the flow vs pressure curves for a pump of this type there is usually an area of operation where a small change in outlet pressure (by increasing the restriction) results in a much larger decrease in total flow. In addition, the left/right side flow balance can be dependent on impeller style and position relative to the pump and scroll, scroll geometry, and external restrictions (the block passages). This balance is not always well behaved, and it's surprising how a small change in one of the variables can affect it.
On second thought, that does look something like voodoo, doesn't it?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks very much to all for your information. I'll check on the water pump.
Paul
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

hose to slow down the flow thru it & improved heater performance greatly. s
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.