coolant flow question...

[jakeb]

Does anyone know if the line that run back to the overflow take from the spider hose is a return back to the engine? Or is it a return from the engine to the overflow tank. I would assume it flows from the tank back to the engine through that hose...but am not 100% sure.

The reason I ask is I am installing a m42 into a 1967 2000c and was not able to fit a radiator with the build in res tank so I just plugged that hose as I THINK it is a return from the res tank which I don''t have. I am running an e30 318(m10) radiator.

jake

[7pilot]

The spider hose is the main drain to the water pump. .

[jakeb]

hmmm, any idea where I can connect it then without a overflow tank? Upper or lower radiator hose?

[RoadHazard]

If you don't have the built in expansion tank, you will need an external one. Just find a place to fit it.

[jakeb]

So should I be able to run the small little hose off the top of the radiator to another tank which then connects to the spider hose....

The e30 318 radiator has a cap on the top tho...then the expansion tank would too...would that work fine?



a quick pic of the swap

[RoadHazard]

Yes that would work. When bleeding the system, you will need to fill coolant at the radiator cap and let it burp there.

[jakeb]

I just went and looked at the radiator that is in the car and I don't think adding an expansion tank is going to work. The overflow line only will work when the pressure pushes the cap open.

So could I Tee the spider hose into the lower radiator hose? Or do something with the cap to make this radiator work differently.....

hmm bummer

[7pilot]

The lower radiator hose feeds to the thermostat and then to the engine. The coolant from your expansion tank would not be cooled by the radiator if you plumb it in that manner.
This would reduce the efficiency of the radiator.

m.

[jakeb]

there is a spot for an m14 connection at the bottom drivers side of the radiator and i am going to try and hook the line to there. The m10 318 radiator doesn't use a expansion tank the same way as the others...it is more of just an overflow.

From what i understand by connecting at the bottom of the radiator i will be bypassing the thermostat a little bit...as the water pump will be pulling from the bottom(cooled) side of the radiator. But that shouldn't really hurt anything.....should it?

[7pilot]

You could experiment, but watch the temp carefully.
The coolant in the expansion tank still won't be passing through the entire radiator circuit.
If the car sees track action, it would be advisable to route the cooling circuit as it is in the stock M42 engine bay.
The M42 most likely runs hotter than an M10 for better emissions, plus it makes more power.
You may run into runaway coolant temps that even a large cooling fan can't bring down. I would use the 80 degree fan switch to give the fan a chance to do some cooling before the coolant temps can spike past the capacity of the fan.

m