could one of you engineering types

[KgB]

what was wrong with having a hose from the radiator go to the core, and the exit to the water pump....wait....that's backwards....waterpump in then out from the core to the rad.

  I do not want hundreds of gallons pumped through my heater core at 4000 rpm.  without bypass, it's just too much pressure:)

[CAP1]

Heater core clogs because of engine block corrosion, design has nothing to do with it. Poor quality metal with corrosive coolant leads to electrolysis-induced heater core clogging.  Others just wrong:)

actually, it's more a lack of maintenance that causes this, not poor quality metal. and yes, design does indeed have something to do with the core clogging.

[CAP1]

  I do not want hundreds of gallons pumped through my heater core at 4000 rpm.  without bypass, it's just too much pressure:)

there have been bypasses on cars for at least 3 decades. and the ones we used to use, actually worked reliably.

[KgB]

actually, it's more a lack of maintenance that causes this, not poor quality metal. and yes, design does indeed have something to do with the core clogging.

The majority of repeat heater core leaks are due to high flow rate or use of poor quality coolant. (Explains bypass.)
Check for voltage in the cooling system by touching the negative contact of a voltmeter to the battery ground or a known good ground and suspend the positive lead in the coolant, making sure it is in contact with the coolant but not touching any metal part of the radiator or cooling system.
I'm surprised you don't know that.

[CAP1]

The majority of repeat heater core leaks are due to high flow rate or use of poor quality coolant. (Explains bypass.)
Check for voltage in the cooling system by touching the negative contact of a voltmeter to the battery ground or a known good ground and suspend the positive lead in the coolant, making sure it is in contact with the coolant but not touching any metal part of the radiator or cooling system.
I'm surprised you don't know that.

i do know that.

 we were at first talking clogged cored. now you're talking about leaking cores.

if you want to go to leaking cores, i've replaced more 95 to present cores than older ones. i think i could safely say that in that 95 and newer group, most of them have been 2000 or newer. when we have all of this newer types of bypasses.

 in fact, the only heater cores i remember replacing(whether clogged or leaking) was in the fox bodied fords. a LOT of them used to clog. and a leaker in my 85 e-350.
 the most common leakers i had were the chevy cavaliers, and the other gm products based on that chassis. ingenious design there. lets use aluminum core with plastic tanks, and inlets. i did so many of them, that i had it down to under 30 minutes....and that's if i was screwing off.

[Skuzzy]

Heater core clogs because of engine block corrosion, design has nothing to do with it. Poor quality metal with corrosive coolant leads to electrolysis-induced heater core clogging.  Others just wrong:)

I was referring to the specific design of the part in question.  Clogging will occur quicker as the coolant velocity is reduced, which helps deposit particles (particles from block corrosion and other deposited particles from the rest of the coolant system), which slows the coolant more, which deposits more particles and so on.

Electrolysis is going to occur no matter what the flow is like.  Actually, allowing the coolant to rest in place will exacerbate the corrosive effects, once electrolysis has started it all.

Damage from old coolant is going to be more of a factor than electrolysis will be.

 I do not want hundreds of gallons pumped through my heater core at 4000 rpm.  without bypass, it's just too much pressure:)

Coolant is not pumped directly from the water pump through a heater core.  Virtually all coolant systems tap off of a feed to direct coolant into the core.  The back pressure is minimal.  The pressure the coolant is under cause more stress than any flow will.

Of course, that assumes a reasonably well designed coolant system.

[CAP1]

voltage is to be expected in a cooling system. .3V and less is pretty much acceptable in iron engines. i think it's just about .1 or so is acceptable in alum. engines.
 deposits in the heater core, and radiator will happen from not keeping your cooling system clean and maintained, regardless of engine build quality.

[KgB]

i do know that.

 we were at first talking clogged cored. now you're talking about leaking cores.

if you want to go to leaking cores, i've replaced more 95 to present cores than older ones. i think i could safely say that in that 95 and newer group, most of them have been 2000 or newer. when we have all of this newer types of bypasses.

 in fact, the only heater cores i remember replacing(whether clogged or leaking) was in the fox bodied fords. a LOT of them used to clog. and a leaker in my 85 e-350.
 the most common leakers i had were the chevy cavaliers, and the other gm products based on that chassis. ingenious design there. lets use aluminum core with plastic tanks, and inlets. i did so many of them, that i had it down to under 30 minutes....and that's if i was screwing off.

I was explaining presents of a bypass not leaking cores. But yeah it's kinda confusing, sorry.
Cap according to you core clogs due to poor maintenance. The damn thing clogs every year, how often does coolant need to be changed?  If for various reasons heater core becomes anode, coolant will corrode engine block.

[Shuffler]

My 98 Z-71..... the tube out of the intake manifold that you connected the heater hose to was made of pewter.

How genius was that. I bought the truck new in 98 and the tube disentegrated in 2000. Replaced it with a steel unit.

[CAP1]

I was explaining presents of a bypass not leaking cores. But yeah it's kinda confusing, sorry.
Cap according to you core clogs due to poor maintenance. The damn thing clogs every year, how often does coolant need to be changed?  If for various reasons heater core becomes anode, coolant will corrode engine block.

i've never had a recurring heater core clog.

 but poor maintenance can and will cost you a lot.

 had a toyota corolla a couple of months ago. looked like it had never been flushed. ever. i'll have to go looking. i think i still have pictures of the crap that came out of that one. it cost him a radiator, and a LOT of flushing.

 i generally recommend my customers to flush their systems once a year. either beginning of winter, or beginning of summer. i do this, because of all of the "better" coolants out there. plain old green antifreeze works wonders, and doesn't make nearly as many problems as dexcool, or some of the other coolants. in fact, i'd have to say that dexcool is most probably the absolute worst coolant out there.
 then there's the G-12 used in vw/audis.......stuff's nearly $50 a gallon!!!!

 basic maintenance on ANY car will alleviate most all problems. the corolla i mentioned, belongs to a customer that brings me a fleet of 8 vehicles. the previous shop they went to pretty much did nothing. these cars were in horrible shape. after about a year, i've got them to a fully preventative stance now. now, they only come in for basic maintenance, or the occasional failure, such as the malibu sitting out there now, "burping" the cooling system.....from a blown hose.
 cool thing is that now their drivers feel confident when they get in these cars......all of them except for 3 have over 200k on them. the malibu out thetre has 291k.

[CAP1]

I was explaining presents of a bypass not leaking cores. But yeah it's kinda confusing, sorry.
Cap according to you core clogs due to poor maintenance. The damn thing clogs every year, how often does coolant need to be changed?  If for various reasons heater core becomes anode, coolant will corrode engine block.

wait? this is from your post i quoted?

 The majority of repeat heater core leaks are due to high flow rate or use of poor quality coolant. (Explains bypass.)

[CAP1]

My 98 Z-71..... the tube out of the intake manifold that you connected the heater hose to was made of pewter.

How genius was that. I bought the truck new in 98 and the tube disentegrated in 2000. Replaced it with a steel unit.

you should see the various 3.8L configurations.

 one has the coolant system going through the alternator bracket

 some have a plastic tube threaded into the intake, which disintegrates. some have a plastic elbow that does the same.

[dkff49]

Because it was funner to make those shapes in a CAD program than something simple and boring?

,
Wab

Plus now it can serve a dual purpose.

You could give it to one of your kids to make a windchime.

[Skuzzy]

you should see the various 3.8L configurations.

 one has the coolant system going through the alternator bracket

 some have a plastic tube threaded into the intake, which disintegrates. some have a plastic elbow that does the same.

Don't forget about the plastic thermostat housings BMW used for many years (not sure if they still do).  Almost always insured the owner would be buying a new engine when it went out.  Of course, it never failed until the warranty expired.

[CAP1]

Don't forget about the plastic thermostat housings BMW used for many years (not sure if they still do).  Almost always insured the owner would be buying a new engine when it went out.  Of course, it never failed until the warranty expired.

are you talking the computer controlled thermostats, or just the plain old plastic ones before the computer controlled ones? which also tend to go bad.