coolant flow

[schliske]

I'm trying to get my heater to work. I've got dual weber 45 dcoe's with a coolant bypass tube, a new water pump, new thermostat, new hoses, flushed heater core and 320 radiator. I had the heater box out and did the flaps, etc. It still isn't clear to me which way the coolant flows through the by-pass tube. Someone mentioned returning the water up to the top (to the water neck?). I don't know if it is possible to get the heater to really "melt your tennis shoes" with this set up like I was able to get in my '70 that had a 32-36 carb. Help?Thanks! michael

[TobyB]

You should be able to fry those Keds. But there are a lot of things that

have to be working really well do do that.

Hot coolant comes off the back of the head, goes into the heater,

then returns to the water pump via the return tube that goes along the block.

So if you're not getting good heat, you're probably not getting good flow. The

engine doesn't rely on the heater for cooling, so if it's not flowing, it doesn't

bother anyone but the cabin occupants.

Sadly, the primary cause of restricted flow is that the heater core's gooped

up. They do that. And they are a royal pain in the arse to get out to be

hot- tanked. We did Jenn's car, and it's always made my Chucks toasty.

If you are getting good flow, but not heat, the problem's either that the engine's too cool (the thermostat's cooling it too much) or that the heater core's silted up. Sadly, THAT fix is to pull the core...

The practical things to check before you pull the core are: Heater flap (make sure it opens) and heater valve (ditto).

They both run on the same handle, but ( I seem to remember) separate cores

so if one cable slips or binds, you'll get reduced heat....

Obviously, you'd wanna make sure your return pipe is unobstructed, but

I'm sure you did that.

hth,

t

[Guest Anonymous]

If you remember when you had a downdraft webber the hose to your heater went from the back of the head to the valve into the heater then out a hose to the water return neck attached to the top radiator hose.

Now with your sidedrafts you have the hose from the heater that used to go to the radiator return hose going to the water pump. Pause for a second. Some how this is going to reverse the flow since the water pump is the highest pressure on your coolant flow system. Unfortunately the pressure at the back of the head is damn near as high a pressure as at the pump. You will get almost no flow!

If you want try getting a copper tee fitting to insert into the return hose to the top of your radiator. Cut the hose put in the tee and run the "return line" from the heater to the tee. Now you are back where you were with your down draft carb set-up and you should be fine.

I was going to do the tee thing on my heater setup but decided to just pull out the heater save the weight put the heater in a box in my garage. The problem with no place for the coolant to go from the back of the head is it turns into a dead leg and the head gets hot. On my list of things to do is to complete the circuit from the back of the head to the radiator return hose no heater involved.

Have fun

[schliske]

The way I understand it (and I could certainly be wrong) the water pump sucks water from the thermostat and the coolant return pipe from the heater and pushes it into the front of the engine. Could someone verify this please? Thanks!

[ifayeoh]

Cooling

All '02 models use the same basic cooling system with a couple of exceptions. All models use an engine driven water pump and cooling fan with a vertical flow radiator and dual action thermostat.

Operation

We'll provide a quick discussion on the coolant flow in an '02 motor for familiarization. Starting at the water pump, the coolant is pumped into the engine block and up through the cylinder head. Most of the coolant exits the engine at the top of the cylinder head, at the hose flange next to the intake manifold. From here, the coolant flows either to the thermostat or to the radiator. If the engine is below the thermostat opening temperature, the coolant flows to the thermostat to warm it up, and from the thermostat it flows back to the water pump and into the engine. If the engine is hot, the thermostat shuts off the flow from the top of the head back into the engine, instead forcing the coolant to flow to and through the radiator. The coolant is cooled as it flows through the radiator and emerges from the bottom hose of the radiator to the bottom half of the thermostat. This cooled coolant then flows to the water pump and into the engine. By using this system, the thermostat controls the temperature of the coolant entering the engine, instead of the temperature of the coolant exiting the engine. This allows for better temperature control and prevents having ice cold coolant from a radiator on a cold day hitting a hot motor when the thermostat opens.

The heater takes hot coolant from a fitting on the back of the cylinder head, passes it through the heater core, and returns it through a pipe or through the bottom of the intake manifold to the water pump, where it is cycled back through the engine. The automatic choke on carburetted cars so equipped takes hot coolant from the back of the block and returns it into the manifold to go back to the water pump. The warm-up device on the tii and the manifold heater on a downdraft carburetted car takes hot coolant from the flange on the head and returns it to the water pump as well.

System Differences:

All '02s use the sa

the above is taken from http://www.bimmers.com/02/

Engine, cooling

Stay Cool!!!

Frank