mk1 radiator boiling water?

Hi guys, ive got a mk1 golf 16v, ive removed the heater matrix, expansion bottle and water pipework on the right side of the engine, and replaced my radiator with a VW topfill radiator.

ive recently started my car for the first time and as the car gets up to temperature stem starts coming from the top fill cap and then water boils out of the lid (like opening a bottle of fizzy pop) i have looked at the cap to see if somethings missing but im unsure, there is a metal washer sort of thing in the lid that comes out, but should this have a rubber one instead or as well as this? is it supposed to be able to pour out the lid and do you guys have any ideas or tips?

the engine temperature says its only getting upto around halfway but i dont dare go pst that to see if the fan will kick in to cool it down as its already boiling out the lid. oh and does the 2 pin sensor at the bottom of the rad need to be different to cope for a different temperating being a different engine or will it be fine? the temperature light is flashing constantly too no matter what the temperature the engines at?

one other question too, i want to wire in a manual fan switch to work as well as my automatic fan, how would i go about doing this? i have a switch in the dash id like to wire it to

so any help would be great, thanks

Firstly I'd check your thermostat and make sure it's not sticking or even opening. The radiator cap is designed to open like this if the pressure gets too great, otherwise you've got a runaway steam boiler - check the numbers on the cap to see what pressure it opens at. Is the radiator large enough to cool the engine now you've removed water capacity ?

sounds to me like you need a new cap, afaik its the same fitment as the normal expansion bottle cap? if so get a blue one, available all over. same as pre-90 mk2 golf as well

I'm having the same problem with my 1.8t i have a blue cap topfill rad and the car's getting that hot the fan kicks in but if i keep going the waters started to push out the pressure cap and boiling over, i don't rate the top fill's i'm going for a mk2 1.8 rad with the header tank with low temp switch and stat to.

i read a post on here not too long ago with same trouble,,he changed quite a few parts,turned out that it was the timing which was out.cam was 2 teeth out and it was running rich if my memory is right.
hope this helps

i got a replacement (used) cap and seal and tried that, it took a bit longer but still boiled up and leaked out the lid.

should the system be air tight? when i squeeze the pipes you can hearair leaking out the cap.

also we still didnt manage to see if the fan would kick in, so we just ran the fan constantly and the car still boiled over after running for 5 mins, but the temperature reading was under halfway, left the fans on and turned the car off til the rad was cold and the temp was upto halfway still, (the temp light flashes constantly, it has since i first started the car a week ago) i get the feeling that either the temp reading isnt correct, or the sensors arent working?

helppp, VW festival in a week and the cars not even running yet

brad moles mk1 golf progress by bradmole, on Flickr

here is my radiator, does anyone know the part number for the thermoswitch or whatever it is at the bottom left in this pic? does it need to be for a 2.0 16v engine or the one for that rad? cheers

im gonna order a new cap, thermostat and housing and thermoswitch

Thats your fan switch mate you can get a low temp one from awsome so it kicks in early than normal one i'v gone for that.

http://www.awesomegti.com/neuspeed-180-f-82-c-2-pin-fan-switch

yes the cap should be fully sealed, try a new one first. if it isnt the coolant cant pressurise and it will boil over

right guys thanks for the help, im almost there now i think, still something wrong but i feel its not something major.

i noticed the top of the radiator above the threads there is a bead around the top where the lid screws onto obviously this is where the rubber seal pushes onto, well part of that lip had broken off on mine, so when i squeeze the pipe from cold you can hear air escaping, i filed the lip down so that the top is all level, put the cap back on and no leaking air, woohoo.

started the car and let it idle for 10 mins, after 5 mins or so the bottom rad pipe started getting warm, so im guessing the thermostat is working, then the fan kicked in, all good. for the first 5 mins or so i left the cap off and squeezed the pipes to try and get rid of any air, once the water started bubbling i put the cap back on and left the car idling for another 5 or 10 mins, the temperature slowly went up to 3/4 and the fan was on from around 1/4, im gussing the car will get upto about that normally if just sitting and not moving to help cool it?

so all seemed normal (except the temp light flashing constantly), then i turned the engine off and water and steam gushed out the cap, why might this be? is it normal? the only thing i can think is that the rad was too full? i left it about an inch and half down from the lid? i could hear the water in the top rad pipe bubbling afterwards for a bit


any help would be great

hmm the fan shouldnt be on till around 3/4, then it should stay on till the temp gets back to near 1/2.

is the rad nice and hot all the way across after the stat has opened?

http://www.vwgolfmk2.co.uk/viewtopic.php?f=37&t=14913

Check the fan kicks in when the gauge gets near 3/4, if not disconnect the plug from the radiator sender in the bottom, passenger side of the rad & bridge the pins. If the fan spins then the temp sender is broken

ive bridged the pins and the rad comes on, do you mean at 3/4 temp try this or just any time? does this mean my temp sender is broken? where is this located, is that the thing i disconnected to bridge the 2 wires from it? what replacement will i need?

where is the fill level for a topfil radiator? just a little bit from the top?

bridging the pins just checks the fan and wiring is ok, to check the sender you plug it back in and watch the temp gauge. the fan should kick in on its own at around 3/4, if it doesnt then replace the switch.

as for level fil i have no idea, it will chuck out the excess if its too full dont worry about that

just read through yoru FAQ on coolant systems, noticed you mentioned this somewhere

hmm maybe you have an earthing problem, clean all the battery/alt/starter wires, any brown wires to the head and also the braided earth from rocer cover to coil bracket (ifd this isnt there fit one)

i dont have a braided earth from the rocker cover to the coil bracket, i moved the coil to inside the car, do i definitly need an earth from the rocker cover to there or can it be put somewhere else? could this be my problem?

im getting leaking from the water outlet on the side fo the ehad beside the coolant temp sensors, ive blanked it with a metal plate and a gasket but its still leaking and getting worse, im gonna get some gasket material and try again

this wont effect the cooling system in any way, if it is a problem it usually makes the dash go loopy is all.

any leaks wont help as it stopsd the system pressurising properly, also since you blanked off the outlet on the side of the head you may have reduced the water circulation thru the head! ideally you want to loop a pipe from the head to the metal pipe on the side, though some people have got away with it

I know plenty of people have done it but isnt blanking off the outlet on the side of the head a bad idea?
Essentially the water is just going to sit inside the head and not flow around to cool it.

MR_LONG said

I know plenty of people have done it but isnt blanking off the outlet on the side of the head a bad idea?
Essentially the water is just going to sit inside the head and not flow around to cool it.

well thats what i thought but it seems people do it? i just dont know if your supposed to do something else too so would like some info on it if anyone could help, really want my car on the road before i lose interest in it

Hi - What radiator is that ? It looks perfect for a 16v carb setup.