upper radiator hose

[air-cooled or diesel]

i have no idea as we had a '79 mk1, i ended up blowing the clutch when i had just got my drivers licence and it died a year or 2 later, lasted a good 15 or so years, i dont remember too much about that model as i was a little young, but the '84 mk1 we had, had a/c so the heater must have been controlled @the vent doors. thats been a while ago, as i think that car saw my sister thru college and later my parents got it from her in cali and drove in back to the east, fixed her up some, only to lose her a few years later, i do miss her, my sis' good girl, she had all kinds of like trinkets and stuff on it, it was funny, had the E for 5th gear. maybe 1 of the first 5th gears vw put in. certainly remember going along @like 65 mph in a 4speed, its unreal by todays standards, revs so high,,

[libbydiesel]

I'm not particularly familiar with the Mk2 Jetta/Golf setup.  Does it allow ambient airflow through the core (from exterior to exterior) when the heat is turned to cold or is the core completely closed off to any airflow at those times?

[air-cooled or diesel]

yea, ive taped up both my mk2s recently; i do suppose both my(our)mk3s will need to be opened and taped up some time, some of the foam is getting out of the vents on them., the mk2, the heater vent door closes off the heater core, i would suppose its hot all the time back/in there, but the funny thing is, if the heater door isnt taped you wont get heat, like none, the air 'can' flow by, thru core, but it takes the straight route of cold vent flow, the heater core is somewhat recessed in vent system, air goes in outside vent, or can be on recirc, as far as i know the recirc is for max a/c setting, air goes thru evaporator, if you have one, then the heater door, closed the air travels straight to the vent door, and then up down, or out vents in dash. with heater door open, full heat, the cold flow is now blocked and the air takes a slight detour to core, then vent curves back some and goes to vent door, and so forth, up down or out vents as vent door is set.

[air-cooled or diesel]

The filter works to keep the bypass restriction from being clogged by a single piece of debris.  It doesn't really matter if it is a restriction.  The bypass line is only there to bleed air.  You just don't want it to plug completely. 

i cannt say i agree; both of my mk2's flow a steady stream of water out of the bypass to the reservoir, as revs increase water stream increases, obviously. theres bound to be some air, mostly froth. after i fill system and burp, usually 2X, theres almost no air i can see, when i watch, i feel its a relief, at top of system, and should improve flow to rad, by the way of relief. if you have less than a steady stream from bypass, your filter needs cleaning or change.

[libbydiesel]

It is not uncommon for small amounts of air to enter any automotive cooling system due to small unseen leaks that allow air in as the system cools and goes to negative pressure.  Most cooling systems safeguard against air accumulating in undesirable locations with the layout of the cooling hoses or by adding small air bleed lines just like the one discussed.  That small hose will assist some with bleeding the air out of the system when the system is drained/filled, but its main purpose is to prevent air from gradually building up in the radiator and nullifying the radiator's ability to cool.  Any flow in that circuit does not 'improve flow to the radiator', it bypasses the radiator and so reduces the flow through the radiator.  If your theory were correct that increased flow in that line helps the radiator, VW would not have installed the restrictor in that line.

[air-cooled or diesel]

although ive heard of the restrictor; ive never seen one on any of the 5 mk1s & mk2s we ve had

[libbydiesel]

It's not an imaginary part.  I have personally seen them.  They were fitted to the original stock hose in that circuit.  If the restrictor is not present, someone replaced the hose without installing the restrictor in the new hose.  With a 25-35 year old car it's not exactly uncommon that the hose gets replaced and and the person doing the replacement doesn't even realize the restrictor should be moved from old to new hose.  The anti-vibration clamps on the injection lines and the timing belt covers are similarly not imaginary either and also server a useful purpose despite many people removing them and never reinstalling.  Did you know that the Mk1 timing covers are supposed to have a little plastic cover part that inserts between the head, injection pump and metal cover?  On 99% of the Mk1s that part is also missing...

[air-cooled or diesel]

like i said ive heard of,,online, and have been in some discussions with it,, but interestingly enough none of our mk1 or mk2's had the hoses replaced or the restrictor. all of them had the oem hoses on them, on the 1 mk2 i just swapped out all the hoses. my other mk2 still has the stock hoses on it,,should have replaced, but i ll do that next time i do the timing belt, hopefully the old hoses will last that long; i cannt say that for the other mk2, blew a water pump, and the 1 hose was so gone, luckly i got to it, and the rest.

[libbydiesel]

You're the original owner of each of the vehicles you assume have the original hoses?  In order for me to believe that you are, please post up the original purchase documentation.  Otherwise, it would be good to stop yanking everyone's chain.

[RunninWild]

How can you tell they are the original hoses and not an oem replacement? These vehicles are old. What's to say the hose wasn't replaced 20 years ago with a dealer part? Are the hoses date stamped?

[libbydiesel]

That's exactly my point.  He would have to have owned the car since new.  Regardless, I'm glad this thread came up.  I know my mk1 does not have a restrictor in it and I should add one and a filter before it. 

[thomas m]

Here you can see the little orifice("plug") near my right thumb and finger. The yellow/tan "stuff" is some gunk that backed up there due to not changing the coolant fluid. Eventually, this blocked the orifice, stopped the flow into the overflow bottle and blew the top off of the heater core. This is from my 1991 NA VW diesel.

[libbydiesel]

That hose plugging won't increase the pressure in the cooling system unless the radiator and heater core are BOTH also plugged.  The pressure cap takes care of the pressure regardless of whether or not that hose is plugged.  That hose just lets air bleed out of the top of the radiator back to the expansion tank.  Regardless, adding a filter pre-orifice as mentioned earlier will prevent it from clogging. 

[ORCoaster]

Libby, two questions regarding the filter you put on years back.  Did you find that it restricted the flow comparable to the restrictor in line?  Any idea what the inside diameter of that thing is? 

Also did you ever notice that the heat of the coolant made the plastic of the filter really soft to the point you thought it would explode if the pressure went up to the point the release in the coolant cap would let it go?  What is that 17 lbs?

I just put one of these on my Rabbit and just going to watch it for a bit and monitor how fast I heat up in the mornings.  I have a great temp sensor on the dash.  Big Blue and Digital. 

[libbydiesel]

I had the filter installed along with the restrictor.  The flow did not seem restricted beyond what the restrictor limited it to.  I ran the single filter on that car for several years (4-5?) and 30,000+ miles until I sold the car to my brother-in-law.  He drove it that way for a couple years and then sold it.  The filter held up that long without any perceptible damage from heat or pressure.