Cant bleed cooling system after replacing seal on thermo housing - tried the usual.

[lobe]

Help,

Read all i can on most forums etc. 2003, 2.0 petrol, 8v APK engine.

Car, heater, cooling system were fine before. Previously, car warmed up correctly & then just sat half way on temp gauge, heater worked very well, no probs.

Changed the thermostat flange (behind the alternator) o ring, as it was weeping v slightly. Simple job, changed the other one on the end of the engine, 4-5 mths ago, there a good sticky on it although it for a jetta on here (the one above gearbox) No dramas.

O ring looked a little squashed etc. Fit new o ring seal to thermo housing. All good, no leak.

Did usual, of having heater on whilst filling, run with cap off etc, squash hoses etc.

This one has been totally different.
Cant seem to get the air out. I've changed plenty of radiators, heads, gearboxes etc in my time and have tried the usual tricks, burping the hoses, removing the coolant res/bottle & lifting higher up. Filling coolant res/bottle whilst having top radiator hose off, until coolant flows etc. Cracking a few hoses whilst its running and hot, make sure no air/steam pockets are there etc. Jacking car up to raise coolant bottle.

Im positive its air. Heater now only blows cool. Was fine before.

I have had it slightly warm out of the window vents on one or two occasions, but centre vents were luke warm. I'm sure ive got a big air/steam pocket in the heater matrix.
Heater inlet hose was hot, outlet coolish, although abit more idle'ing with cap off, burping hoses etc, seems to have helped and outlet is warm/hot (although not as hot as inlet (understandable). Still doesnt blow warm though like it did/should.

I flushed the cooling system, 6 mths ago, refill with fresh G12 etc. System bleed up fine in my drive way, no probs at all. No such probs when i changed the other housing (with temp sensor in it) either.

Car in exactly same position on fairly level drive way. Tried facing it up a slope with cap off, burping hoses etc.

Took it for a run a few times, around after having it running in driveway for ages, first run temp gauge went up off half way. Came home, let it cool, cap off, more burping of hoses. Repeat a few times, temp more or less staying on half way now, so not too bad.
Quick run up motorway, let it cool down, then check bottle again, burp hoses, run on fast ish idle till warm, still no heater !!!
When letting it cool from hot, can hear gurgling in area of heater matrix hoses, hoses that run from housing to top hoses of radiator.

Even tried a new thermostat i had in it, exactly same. Water pump etc all good before too.

Any ideas, am thinking, crack the heater inlet off, maybe a little compressed air and a long length of clear hoses with coolant in, see if i can push water through the matrix.

Any idea's ???

[Back Door Shenanigans.]

Weird, The only thing i can think of is there's crud all blocking up your heater pipes. Maybe try taking the heater outlet pipe and seeing if any waters coming out and if not then the intake and see if its the heater core or something more sinister.

[Jmac]

Unusual for a mk4 engine not to bleed, they pretty much take care of themselves after a basic bleed, never any need for the old skool bleeding like an old Audi needing jacked up etc, sounds like you stat may have decided to stay stuck open or is opening way too soon keeping the core temp down, you say all the components are good, thats cool but a sanity check is reqd i think, squeeze the rad hose and crack open the throttle and you should feel good pressure build up from the water pump, im sure t is but this is a 2 sec check. Next only ppther thing coming to mind after you have obviously dropped out the coolant to do the seal, perhaps there was gunk in the heater matrix and when the coolant level has dropped it has allowed the gunk to block off the core. rare but a chance, id be suss on stat myself. you should have hot in and hot out on the bulkhead and you should feel the pulse as you burp the pipes.
Im sure you are doing this with no AC too hey?got to ask

Good luck there
Jmac

[lobe]

Thanks jmac.


Spent a good part of today on it too. Bleeding, crack hoses etc. All to with no success. Hoses seem fine and pressure up, but not ridiculous like when head gasket is gone on a car. I can feel hoses pulsing as you say, when applying throttle.

When fans come on - 2 marks over half way on gauge (prob about 2/3rd's to fully hot ) hose to t-stat is hot so am guessing its open and flowing. As it cools to middle on gauge, t-stat hose is then cooler, i.e radiator and system is cooling it down, as normal.

Cooling systems always been clean and car was looked after by vw then, vw/audi independent garage prior to missus buying it, 8 mths ago.
I had no bother filling/bleeding after flushing the cooling system 6 mths ago. Hoses off, good flushing and not tap water either, Correct G12/water mix added. All good, it was pretty clean, i just wanted to be sure it had fresh G12 in.

Not sure if heater core is blocked. Inlet is hot, outlet feels warm/hot too.

Take it for a drive and it goes up two notches then fans kick in and bring it back to half way again.

I put a new thermostat in it when i changed the o ring 1st time around. Same deal. Couldn't get the heater hot. Was abit pushed for time,, suspected new t-stat, tested it and it didn't seem to open in a pan, so put the old one back in as had no real problems with this one as it all worked before.

Any ideas ? i cant crack the heater outlet off, because its under the fire wall and has a clip on it which i cant get to with normal grips. Am guess VW have special hose clamp tool.

Maybe i should try putting the old thermo housing back on - its the only thing that's changed really now. Side by side, the new and the old looked identical. New housing is Vaico - german one, not a crappy chinese knock off, old housing was original VW item.
New t-stat is identical to old one, letter markings, everything. Its a Behr one and both parts were bought from specialist german auto place - HSY. Am guessing the old t-stat is Behr as HSY supply parts to the indy german garages here in Adelaide.

Maybe old thermo was just slightly playing up, prior to me working on car ?
I did notice car move up off half earlier in week when i took it for a spin up the motorway (after cleaning MAF as idle wasn't as good as it normally was) but only under load a on a massive hill and only moved up one notch. Came straight back down.
I though the slight leak at the t-stat housing might not be helping and causing system to loose pressure when on a motorway blast, screwing with the t-stat momentarily. Thought i'd fit a new t-stat whilst fixing the leak with a new o ring and housing.

When the new t-stat was in, i had exactly the same problem as now, temp going up off halfway point and no heater, hence why i swapped it out and put the old one back in.


Any idea's ???

[Jmac]

If you have 2 hot heater pipes you can assume its flowing there, you are testing this with the ac off yeah?? even if you have selected hot with the controls inside it may in fact not be and a blend door not closing or opening properly dash side?? sounds like all is well engine side mate
Jmac

[lobe]

Thanks for the reply jmac,

Yep ac def off, heater turned upto to hot. Have tried tweaking controls, toggle ac on/off etc in case was a glitch etc, stuck heat control etc.
Not sure how these heater controls work on this car but on my old e36 you can hear them flick over as you turn the heat on to allow the hot coolant to flow to them and when you turn on the ignition.

Is there any thing i can adjust manually on/behind the heater controls to ensure coolant flow, fuse relay etc? I checked the carpet, to ensure core want leaking.

Somethings a miss as car never used to run above half way on temp gauge, not matter how you drive it.

Am sure w/pump is ok as it was before. When i pull small 10/12mm hose which tee's in from the heater inlet hose into top rad hose, plenty of coolant flows.

When i changed the t-stat & housing, i disconnected the alternator wiring, so i didn't touch it with my ext. bar and 10mmm socket. I disconnected the battery before this.

Its like the heater control is doing anything when you turn it up hot. When you turn it cold, the air is cold. AC is cold.

Then again, temp runs over half way and some, when i drive it. It never did this before i started this saga.

Maybe the h/gasket was on its way and this process has made it worse, not allowing heater to bleed out properly. Then again, both hoses to heater feel hot? Supposed outlet hose could be hot from steam/air and not flow.
No water in oil/oil in water but then again, have seen that before on blown h/gaskets. Hoses aren't at bursting point though like when a h/gask has gone.

[lobe]

Jmac,

Thought about what you'd said and i'd not checked for a pulse in the top rad hose from cold. A quick check of the car when cold, start engine, let all get around for a few minutes, rev hard - couldnt feel any pressure or pulse in the top rad hose from the pump.

Priced a belt kit, tensioner, w/p from HSY and will get it all done with some fresh G12/dist mix.

HSY parts confirmed - latest w/pumps (Ks or GS brand i think he said) have a brass or such type impeller & are also fixed on the shaft (keyed or spigoted etc). Previous ones were same material but could still spin on shaft, generation before that were/are of the plastic non metal type and can break or spin.

Confirmed with the indy vw place who has looked after car for quite a few yrs prior, that yes, the pump was changed with the belt. At 172k's milage he said yes, the pump as is due again & confirmed my thoughts with the material type used. He said it would have been the old plastic type fit. With my description, he said its classic w/p prob. Said the sometimes break abit allowing spin. I guess if they just crack slightly - the interference fit of the impeller onto the shaft obviously opens up etc.

If it was just the heater problem i had, I'd borrow my mates hose clamp grips and crack the awkward heater inlet and outlet hoses off. See if i had a steam bubble in the matrix - unusual though for these mk4's.
As i have a temp problem running up 2/3rds under load, up a hill etc - it points to w/p after double checking on a lot of forums etc and with no flow in the top hose etc.

W/p must have been on its way out, hence the thermo seal leaking abit, with the pressure build up in the block.

Just hoping the impeller is in bits when i take the belt & w/p out !!! - and not the h/gask

[JustCruisn]

I'd be praying the impeller is just cracked but still in 1 piece.
Chasing down bits of broken plastic through out the cooliing system could be a nightmare.