4 replies to this topic

[nicklouse]

ok we know what people say you should do- fit the return to the top hose if you are not running a heater.

i have always run it to the bottom hose. why well aint it just like not having the fan on?

 

so lets look at the two set ups-

hot water is mixed and fed to the rad and cooled. (top hose)

hot water is fed to the rad and then mixed with hot water (bottom hose)

 

the rad will cool the water by the same amount  however it is routed.

 

so i would say that the bottom hose routing would run slightly hotter. this is why you hear people say the hose needs a reducer in it to limit the amount of uncooled water entering the cooled water.

 

now on a race car this could be beneficial with quicker warm up times and with a good big front mounted rad the cooling should not be an issue on a sprint hill climb car with a smaller rad as the time running is in minutes or seconds it should not be an issue.

 

so why this post. i am changing my routing from bottom to top hose and i was just wanting to put thoughts down. 

[timmy850]

The old style heaters use a tap on the head, so when the heater is off all the coolant goes through the radiator. When the tap is on the coolant goes through the heater matrix and is cooled.

 

Did any of the later cars ever have a heater installed without a tap in the system somewhere?

 

The heater core will always act like a secondary radiator, even if the fan is not on.

 

The best way to test all this would be install some temperature probes:

Top hose

Bottom hose

Heater takeoff on head

 

My experience with all this was when I hooked up the alloy inlet manifold. Not thinking about what I was doing, I took the coolant from the heater takeoff on the head, then to the inlet manifold and then to the bottom hose. This made a great radiator bypass system, which was fine for 90% of the time, but when the outside temps were getting up over 30 degrees it really struggled to keep my 998 cool. I have since added an engine bay mounted heater to the car and it runs really cool now. 

 

I don't think for a hill climb or sprint car when your run time is measured in minutes it will make any difference at all. 

[dotmatrix]

I use my car for hill climbing/sprinting and I have plumbed the heater take off into the top hose on the radiator side of the thermostat. I have a large front mounted radiator. this works really great as I was having problems with the water boiling in the expansion tank when I was done racing and these problems are now gone and I think this water routing among other things have fixed this problem. The next time I get a radiator recored or in for a repair I will be putting in a hose-connection in the far end of the radiator so that I can route the heater take off hose directly to the top of the radiator.

[Retroman]

Nick you will be right in that the hot into the bottom hose will mean less effective cooling as it will be going straight back into the block.

 

If you run it through a decent front mounted heater core between head and btm hose it drops engine temp by 5 degrees.

 

Never tried routing into a top hose but it should work better.

[nicklouse]

now lets bring in the MPi. what happens when the heater unit "tap" is closed?

hot coolant is dumped straight into the bottom hose. at a time when you would have thought you wanted more cooling.

 

on every car i have run or built i have take from the head to the bottom hose and never had an issue.

 

But as i have changed my breather set up and i have made up a different take off and i have a T piece being sent over i will be feeding it into the top hose which , i know cause everyone says it is, will be better. but i never had an issue. even the MG challenge Metro went heater take off to bottom hose. back in the days pre dry decking blocks.