whats the primary job for the top header tank hose? i have the bottom header tank hose teed into the botton rad hose, but wanted to know what the job of the top hose is so i can work out somewhere to tee into? is the header tank full at all times? or is the top hose only used during expansion of the coolant! cheers

[Edited on 30/3/11 by daniel mason]

On the Sierra I was under the impression it is the bleed point for trapped air into the expansion tank therefore allowing water from the tank to replace it. Therefore generally from around the top of the engine and close to, but on the engine side of the thermostat.

I could be completely talking B****cks through lack of knowledge.

Cheers

Adrian

the top hose should go to the thermostat housing and/or top of radiator (basically the highest point. it gets air out of the cylinder head, seperates air and water so only coolant gets into the engine.

on my engine, the bleed point on the top of the thermostat housing also gives the thermostat bypass, which is esasential to cooling and filling

[Edited on 30/3/11 by blakep82]

on the s2000 the thermostat housing is low down with a large outlet to bottom rad hose.and one of the heater hoses, which i have now bypassed. the water outlet cover is higher up the block an feeds the top rad hose

ooh, right, japanese engine isn't it? if the radiator has a pressure cap on it, as the japs usually do, then its not a header tank system you need, but an expansion.
the way yours sounds, air should collect in the radiator, and then come out of the radiator cap, into an expansion bottle which has some coolant in it. air comes out, and when the system cools, it sucks coolant back in to replace the air.

pwl on here has a header tank and runs the top header hose into a pipe which runs along the throttle body to valve i think?
my rad has no cap by thee way. its a pro alloy rad

[Edited on 30/3/11 by daniel mason]

ok, on my engine theres a bleed point just above the top hose outlet on the block, that goes to the header tank, as does the one out the radiator. i'll get a very crude photo up in a sec, of when mine wasn't quite fully fitted

terrible photo. but it gives you the idea


any air that gathers in the top of the enigne or radiator is piped to the top of the header tank, which should be the top of the system. any air is pressurised in the top of the tank, and if it gets too much, comes out the cap, that way you don't lose any coolant

[Edited on 30/3/11 by blakep82]

so if my bottom header tank hose goes to the bottom rad hose. can i pipe my top header tank hose into one of the hoses at a high point on the engine? thanks for the help by the way

here is a picture of the s2000 cooling system

thats right. basically, the header tank connections should go to the highest point of the cooling system to make sure no air can get trapped in the cylinder head.

the top connections on the tank are there to get air out the engine and radiator

so with my large bottom header tank hose teed into the bottom rad hose, which of the hoses in the diagram would you tee the top header tank hoe into?

i always struggle to work these diagrams out, but generally, whichever is at the top of the cylinder head.

if you look at the diagram though, the pressure cap in on the radiator, so usually, thats at the top of the system, and thats it. maybe worth a u2u to pwl if he's done it already. where's the water outlet cover? if that on top of the cylinder head i'd go with that. my engine is designed to run with a header tank though, so its easy, but yours isn't really

If you look carefully at the diagram the top rad hose goes into the outlet cover. It's labelled on it but the writing is small

[Edited on 30/3/11 by daniel mason]