Should pipe from rad cap to header tank be hot?

[email protected] · 18-04-2016, 19:02

Hi

Fitted an alloy rad yesterday and was just having a feel about today and noticed the pipe from the rad cap to the header tank was warm. Should this be happening? Is it normal and is just firing coolant back to tank? Or have I got a problem here?

Cheers

[email protected] · 18-04-2016, 21:47

Anyone?

swinks · 19-04-2016, 11:06

Yes, should be warm.
Purpose of this pipe is to carry excessive coolant to expansion tank once valve in the rad cap opens at set pressure. It's natural for coolant to expand under temp and build pressure, hence you have valve in the cap which opens under pre-set pressure to let excessive coolant out (to expansion tank).
Once engine is cooled down, the negative pressure builds up in system and valve in rad cap opens (it's two-way valve) under vacuum, sucking back coolant from expansion cap. For that reason you have two marks on tank "max" and "min".
So, if excessive hot coolant is pushed out to tank, hose should be hot from coolant.

[email protected] · 19-04-2016, 17:09

Excellent mate. Thanks for the help. Least I know I have nothing to worry about lol.

foreskin fred · 20-04-2016, 00:15

It's 'cos it's broken.

Barry P. · 20-04-2016, 18:14

Probably worth doing a head gasket check, they push fluid into the expansion tank when the head gasket is on its way out.

18-04-2016, 19:02	#1
[email protected] BooooooosT Join Date: Mar 2016 Location: Recaro, Scotland Car: Scotia White 6 GSR, stock-ish Posts: 125	Should pipe from rad cap to header tank be hot? Hi Fitted an alloy rad yesterday and was just having a feel about today and noticed the pipe from the rad cap to the header tank was warm. Should this be happening? Is it normal and is just firing coolant back to tank? Or have I got a problem here? Cheers

19-04-2016, 11:06	#3
swinks Senior User Join Date: Dec 2009 Location: Lincolnshire Car: ex-Mitsubishi Galant VR4, Mitsubishi Lancer Evolution 8 FQ300 Posts: 326	Yes, should be warm. Purpose of this pipe is to carry excessive coolant to expansion tank once valve in the rad cap opens at set pressure. It's natural for coolant to expand under temp and build pressure, hence you have valve in the cap which opens under pre-set pressure to let excessive coolant out (to expansion tank). Once engine is cooled down, the negative pressure builds up in system and valve in rad cap opens (it's two-way valve) under vacuum, sucking back coolant from expansion cap. For that reason you have two marks on tank "max" and "min". So, if excessive hot coolant is pushed out to tank, hose should be hot from coolant. __________________ ex-Galant VR4: 269 WHP and 325 LbFt torque at 0.9 bar (stock engine, turbo and ecu) Evo 8 FQ300: 351 WHP and 415 LbFt torque at 1.6 bar Last edited by swinks; 19-04-2016 at 18:18..

20-04-2016, 00:15	#5
foreskin fred Registered User Join Date: Apr 2014 Posts: 625	It's 'cos it's broken. __________________ Just tell yourself over and over again "I've been conned". Eventually it'll sink in.

20-04-2016, 18:14	#6
Barry P. Senior User Join Date: Feb 2003 Location: Somewhere on a race circuit. Car: Red Evo IX GT, Silver Evo 2 GSR, Radical SR3, Van Diemen Formula Ford,and a big "Datsun". Posts: 8,743	Probably worth doing a head gasket check, they push fluid into the expansion tank when the head gasket is on its way out. __________________ "Welcome my son,welcome to the machine."

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18-04-2016, 21:47	#2
[email protected] BooooooosT Join Date: Mar 2016 Location: Recaro, Scotland Car: Scotia White 6 GSR, stock-ish Posts: 125	Anyone?

19-04-2016, 17:09	#4
[email protected] BooooooosT Join Date: Mar 2016 Location: Recaro, Scotland Car: Scotia White 6 GSR, stock-ish Posts: 125	Excellent mate. Thanks for the help. Least I know I have nothing to worry about lol.