What are heat exchangers?

[jlawrence54]

All,

I have a 2000 Boxster S. I had the coolant pump go south and bolted on a new one, as well as a new serpentine belt. It still overheats. I have read some stuff on this site that wised me up to the possibility of debris from the disintegrated prop blades in the old water pump still being in the coolant channels, thus causing a clog. Someone suggested I pull the thermistor housing since the bits and pieces may have gathered there. They also suggested doing the same for the "heat exchangers". I have scoured my manual but cannot find any reference to a heat exchanger. Any thoughts on what else they may be called? Also, any advice on how to "burp" the coolant system to get air out, I understand that needs to be done as well. Thanks for any help you may provide.

Jim

[Flavor 987S]

Maybe they meant to say "heater core". The air cooled Porsches have heat exchangers to bring warm air into the cabin during the winter. It works great and very fast in my 1997 911 Turbo.

[san rensho]

Originally Posted by jlawrence54

All,

I have a 2000 Boxster S. I had the coolant pump go south and bolted on a new one, as well as a new serpentine belt. It still overheats. I have read some stuff on this site that wised me up to the possibility of debris from the disintegrated prop blades in the old water pump still being in the coolant channels, thus causing a clog. Someone suggested I pull the thermistor housing since the bits and pieces may have gathered there. They also suggested doing the same for the "heat exchangers". I have scoured my manual but cannot find any reference to a heat exchanger. Any thoughts on what else they may be called? Also, any advice on how to "burp" the coolant system to get air out, I understand that needs to be done as well. Thanks for any help you may provide.

Jim

Did the impeller break to peices and plastic bits were pumped through the motor and cooling system? If thats the case, be careful. Jake Raby has some horror stories of cracked heads and blown head gaskets because the impeller bits clog the water pasages in the head and cylinders leading to overheating.

[jhandy]

did you open the bleeder valve?
with the car running, are you able to get hot air withthe heater on? If no hot air, then there is air in the heat exchanger. Either way, you need to bleed the system by letting the air out.
The bleeder valve is under the false floor where you fill the oil and water.


check and fill the coolent level when the car is cold. Use porsche coolent or the other approved types. usally the "lifetime" and "add to any color coolent" are ok. after you fill it, open the bleeder, then go drive the car for 20 min. allow it to cool fully and then top off the coolent tank if needed. Leave bleeder valve open for a few days.

Only open the tank when cool, otherwise it will over flow and you have to start over.

Make sure the top is on tight.

[stateofidleness]

Maybe they thought you had a 914

[clickman]

The heat exchangers referred to may be the oil cooler on the top of the engine. Or, of course, the rads...

[jhandy]

Heat Exchanger (Heater Core) Boxster 986
Part #:997-572-129-00-M262

they are talking about the heater. If it blows cold when the car is warm, you have air in the system.

You need to open the bleeder valve and fill tank and needed.

[mikstew]

A heat exchanger is a device used to transfer sensible heat from one fluid to another by means of convective heat transfer. There are many different implementations but the most common is metal tube and fin, the purpose of which is to maximize the surface area upon which both fluids make contact. In automotive applications this is typically done with a gas (air) on the shell (external) side, and a liquid on the internal side (coolant for your heater, CFCs for your air conditioner).

As a chemical engineer I had to answer this one

Two possible reasons why you are overheating: debris is causing a blockage, or you have air the system. One is a lot easier to fix. Air is a ****************ty heat transfer fluid and thus will not keep your car cool (hence why we all switched to water cooled engines in the late 80s). Also note that the symptoms of both are the same. In other words if your heater is blowing cold when your car is hot, you do not necessarily have air in the system, it could still be a blockage.

Let the car cool. Take off rad cap and start the car, allow to run for 30 sec, add more coolant while running. This will help displace any trapped air. Also someone said there is an air bleeder valve in the system, use that, itll help. As someone else suggested, be careful about running too long. The thermostat will only measure temps in one location, while you may be boiling off coolant at or near the cylinders (which would be VERY bad)

[smshirk]

Originally Posted by mikstew

A heat exchanger is a device used to transfer sensible heat from one fluid to another by means of convective heat transfer. There are many different implementations but the most common is metal tube and fin, the purpose of which is to maximize the surface area upon which both fluids make contact. In automotive applications this is typically done with a gas (air) on the shell (external) side, and a liquid on the internal side (coolant for your heater, CFCs for your air conditioner).

As a chemical engineer I had to answer this one

Two possible reasons why you are overheating: debris is causing a blockage, or you have air the system. One is a lot easier to fix. Air is a ****************ty heat transfer fluid and thus will not keep your car cool (hence why we all switched to water cooled engines in the late 80s). Also note that the symptoms of both are the same. In other words if your heater is blowing cold when your car is hot, you do not necessarily have air in the system, it could still be a blockage.

Let the car cool. Take off rad cap and start the car, allow to run for 30 sec, add more coolant while running. This will help displace any trapped air. Also someone said there is an air bleeder valve in the system, use that, itll help. As someone else suggested, be careful about running too long. The thermostat will only measure temps in one location, while you may be boiling off coolant at or near the cylinders (which would be VERY bad)

Even though I love the Boxster and the 996 I had, I still wish Porsche had stuck with the aircooled engines. They finally solved the AC issues with the 964 and 993, and the 993 was darn near perfect, top end issues notwithstanding. In addition the aircooled engines were hand assembled and made to last forever. Our M96 engines just aren't as good with Porsche going mass production. The upside of that is more folks can drive Porsches and they are immensely more comfortable as daily drivers, but the sound and fury of an aircooled engine especially still calls those of us who started out with VW's and moved up to Porsches as we got older and had more money. It's true they run 20-30 degrees hotter than water pumpers, but the engines were no worse the wear for it. Even stuck in rush hour traffic in deep south summers, my 911 handles the heat much better than I do without real AC. It now sits all summer and is mostly a late fall early spring car, but I can't bring myself to part with it.