I am doing a coolant re-route for the 96 1.8 that I am working on for my 91. I have read that with a re route the best(coolest) place to pull coolant for the turbo would be at the front of the head where the old thermostat location gets plugged. I was wondering if it would be a beter location to pull the coolant for the oil cooler as well.
As you can see with the pictures attached I was debating on drilling/tapping two 1/8npt holes one each for the turbo and oil cooler into the 3/8 alu cover plate I made. Would it be ok to just have one tapped fitting that runs to a T to supply the oil cooler and turbo or would this result in too little flow to properly remove the required heat from the individual components?

 

looks like it could work...but 1/8 npt with a tee might be to small. I would run two 1/8 npt to each...

 

Or 1/4 off the plate with a 1/8tee I guess could work too and might fit better.

For the heater core I have already drilled and tapped the head so that the coolant supply to the heater core will be right before the thermostat. I am using the basic spacer from Moss and was wondering if I could drill/tap it for the heater core return. Since the DP across the thermostat will drive the flow through the heater core it should work. I just don't know if this would be the best or if it would work at all. I want to say I have read of someone doing it this way, but can't find the thread.

I am trying to eliminate the heater core return to the waterpump inlet and avoid heat baking into the coolant system by the exhaust header.

 

Probably give you enough flow for the head, but very little heat after the coolant warms up and the thermostat opens. Got warm Winters where you are?

 

Warmer, bust I still like heat in the mornings. That is what I was worried about. I wonder what the DP is accross a thermostat like ours when it is full open. Where would be the best place to return the heater core flow then? Other than the mixing manifold. I don't like the idea of mixing hot coolant with the not so hot coolant coming out of the radiator.

 

If you return your heater core to any place that drains to the upper radiator inlet rather than the water pump inlet, you've effectively bypassed your thermostat. The engine will take half of eternity to warm up.

 

As someone who has the heater core returning to the upper radiator hose and not the lower one I can 100% vouch for Joe stating that it will take half an eternity to warm up. For reference over Christmas I drove down to my parents house which is a 3 hour drive when it was 15degrees out. I let the car warm up tell it was out of Warm Up Enrichments for MS. About 45min into the trip the water temp guage was back to reading at C instead of being at 11:30.

 

Wow, I didn't think it would be that bad. I'll have to go do some more reading and come back with more questions. The problems is that I have read so much on re-routes, that I forget what worked and what didn't. I always wanted to try a three way valve that will allow me to have one routing for daily driving to the mixing manifold I guess and then an alternative routing for track that will mix it in somewhere before the radiator inlet.