Gti6 coolant nightmares

[stu28stu 1]

Hi

 

so this lockdown has given me time to get round to sorting my 205 out , 

 

i have the engine in and all is well fires first time all electrics work etc

 

however the cooling system has me in bits ,

 

i am not running a heater matrix as the shell was completely stripped when I started the project, 

so 

radiator is plumbed in correctly 

as is the radiator return to the back of engine 

 

what I am not convinced on is ...

expansion tank is teed into the black metal pipe just below stat 

the stat rear pipe is into the other side of the tee from expansion tank 

 

But when I try bleeding the system I get some air bubble and clear through the expansion tank as I leave cap off 

 

however I don’t get a constant stream of water from the stat bleed valve 

only seem to get water if I rev slightly , which does force some water/air out but when I check again again I can open the valve fully and no water ?
 

all pipes are hot and radiator and if I turn the fans on the temp does go down so there must be some flow round the system ,

dash said on 45 degrees yet the coolant is boiling after maybe 10 mins max 

 

check stat that’s working

water pump is working

no head gasket leak 

 

can you really get air locks that bad ?
 

[welshpug 1,657]

plumbing sounds fine, never had much of an issue bleeding a gti6 in a 205, in a 306 I add a big funnel wedged into the fill point to create a head of water which will push all the air out.

 

one thing I always do with any thermostat is to add a 3mm hole either side of the valve just in from the seal to aid with bleeding the top hose.

 

 

do you have the radiator bleed off pipe that goes back to the expansion tank?

[stu28stu 1]

Ok so plumbing sounds ok then 

 

yes I have the small hose from top left if looking at car returned to the top left of the expansion tank ,

top right hose on expansion tank is sealed.

 

should the water really boil that quick in a gti6 ?
 

and should you always have a steady flow out of the bleed valve when open at all times ?
 

 

[stu28stu 1]

So bleed using the coke bottle method and got a load of air out !
 

changed extension bottle cap and she ran up to 77 degrees 

then started to overflow/boil out througH the cap So had to put the fans on and cool down which it does fairly quick 

 

but she should just be able to sit at idle and not overheat 

 

what can I be missing ????

[allanallen 528 2 Cars]

Is it boiling or is it gassing up and blowing coolant out of the overflow? Is the cap a good one or is it weak and not holding pressure in the system? 
 

with the gti6 I added a self bleed take off to the thermostat housing (like the mi16 and 8v have) that ran back to top right of the header tank, you literally just pour coolant in and pump it all round by squeezing the top rad hose, very straightforward. 

[stu28stu 1]

It blows it out the overflow on the tank just below the pressure cap , 

 

just seems odd

 

as temp says 77 degrees when this happens 

yet thermostat is open as fluid is passing through radiator and I thought that opened at 83 degrees 

 

also how did you make a self bleed valve ?

 

[welshpug 1,657]

a headgasket failure is far from uncommon with these unfortunately, I've changed them over 10 years ago from original steel gaskets letting go in the corner near the water pump, they dont often mix oil and water till its really blown.

[welshpug 1,657]

thermostat will start opening at high 70's and be fully open at 83, but it really shouldn't be blowing it out that cool,  I would be checking the coolant for combustion gases.

[stu28stu 1]

Will check again for gas in the coolant ,

sniff tester didn’t pick any up but it’s worth a double check 

 

will a gti6 just sit at idle and hold a temp ?
or does it always climb when sat still and need fans 

[Anthony 1,003]

29 minutes ago, stu28stu said:

will a gti6 just sit at idle and hold a temp ?
or does it always climb when sat still and need fans 

 

Sitting stationary it will climb to the point where the fans kick in, which will provide airflow over the radiator to cool it down to the point where the fans turn off and then it'll keep cycling.

 

Most engines will behave that way, just varies how quickly they  heat up - and in my experience of GTi-6 205's, they do seem to get hot fairly quickly compared to an 8v.

[stu28stu 1]

Ah ok so sat stationary even just idling they have a constant cycle of fan use to stay at temp,
 

so I guess fan demand is around 90 , 

 

that’s useful to know well I just gotta sort the coolant issue first lol 

 

new cap ordered at 1.3 bar which should be more than enough 

so will start again when it arrives 

 

 

[welshpug 1,657]

standard turbo diesel 205 and gti6 are 1.4 bar caps, I think the gti used 1 bar.

 

basically increases the boiling point.

[stu28stu 1]

Thanks for info !

 

I thought it was 1.1 bar as standard ok no drama will get a higher rated one