over heating

[albsure]

hi guys, al b frustrated, i need help with my 91 jetta eco diesel
 after changing the thermostat, coolant pump, sensor in the bottom tank of the radiator, and the belts, i'm still overheating. i can see it boil up in the round ball type resevoir tank, and then start spitting out of the side of the reservoir. i didn't know that these reserviors were vented or are they not, or do they have blowout plugs for when the pressure is too high. the cooling fans come on only when the AC is on but thats it. did i get a bad thermostat, ok but the fan should still come on. THE ENGINE RUNS GREAT!what do i look at next ? any one have an idea. its hot here all of the time can it run without a thermostat ? HELP :oops:  :cry: ALL THOUGHTS ARE APPRECIATED.

THANK YOU

[vwmike]

the reservoir is not vented. The only time coolant should come out is if the car really does overheat. Is the bottle cracked or is the rubber seal on the cap damaged? How far up does the needle on the gauge go before it starts pissing coolant? If you start it up when fairly cold and take the cap off of the reservoir do you get air bubbles coming out?

[albsure]

hi vwmike and thank you for your reply. i'm not sure if it cracked or the seal but its right at the very top left where if you pull off the plastic sheild appears to be 2 deep concave indentations ( vent holes ) ? i'm not sure i will check bottle and seal at 1st light theneedle is just past 1/2 when it starts to gurgle and then it starts to spit.
yes you get some bubbles and  the water appears to siphon up and down

[jtanguay]

just a guess... but is your fan working?  Maybe there is something clogged in the rad.

my rad fan died... and it overheated and coolant boiled out of the engine

[albsure]

hi jtanguay and thank you. the fan only comes on if i turn the AC on.
it does slow the process, but evevtually it starts gurgling and spitting out of the side of the reservoir.

[dieselpete]

why don`t you try shorting the wires at the rad thermoswitch, and see if your fan works on the hi speed (since you know your lo speed works when the ac is on)- this will at least eliminate the electrical side as a problem area
next how much pressure do you build up and how quickly- on a cold engine do you get pressure right away, any mixing of oil & coolant- that may be a head gasket issue
finally as someone suggested maybe the rad is plugged, and the coolant doesnt go through the area where the thermoswitch is located- hence the fan doesn`t come on
hope this helps- report back



                                                 cheers

[91 ECO]

I have installed a bad thermostat in mine (must have been stuck open b/c the engine would never get up to temperature).  When mine was running a little too hot, it was a clogged radiator.  Replaced the radiator, no problems since.

[albsure]

hi dieselpete and thank you.i'll try the switch thing as soon as i send this reply.

after running for only a few minutes you can see the siphoning action in the reservoir tank and then a few more minutes it stsrts gurgling and steaming and spitting from the side of the reservoir ball. there is no water in the oil or oil in the water. thats a good thing. i will take off the top hose and take the thermal switch out of the bottom of thr rad and see what kind of flow i get through the rad. the car is not at my house so this will take me about a 1/2 hour and then i will report right back. i'll wait a few minutes before i leave in case you have more input, questions, or suggestions.

[albsure]

thank you 91 eco i'm going to check for flow and short the wires at the switch right now i will report back shortly

[addautomotive]

Does the car overheat if you're moving, or only when it's sitting there. Could also be an airlock in the cooling system. After changing the thermostat, I usually unhook the top hose from the rad and pour coolant into the engine with it, then pour coolant into the rad.

[albsure]

thank you for the input addautomotive. ok 1st i started it up and pulled the plug at the thermal switch shorted the terminal and the fans came on . then i shut it off removed the top rad hose and the thermal switch and put a garden hose down the rad hose and water seemed to flow nicely.put the hose back on the engine then disconected the hose from the rad  stuck the garden hose in and flowed water back the other way. water flowed out of the reservoir ( top off ) i did not get water out of the upper rad i guess because the thermostat closed. if it is working properly.it is new but i have bought bad ones.? closed everything and started it up i got a few bubbles in the res. pretty much right away. after a few minutes the temp gauge was between 1/2 and 3/4 and it started gurgling and spitting hot water out of what does appear to a vent holeor blowouthole feature in the res. upper and lower rad hoses were both hot and the fans never came on. so what do you guys think could i have gotten a bad thermal switch and a bad thermostat. i dont know :oops:  

[albsure]

thank you for the input addautomotive. ok 1st i started it up and pulled the plug at the thermal switch shorted the terminal and the fans came on . then i shut it off removed the top rad hose and the thermal switch and put a garden hose down the rad hose and water seemed to flow nicely.put the hose back on the engine then disconected the hose from the rad  stuck the garden hose in and flowed water back the other way. water flowed out of the reservoir ( top off ) i did not get water out of the upper rad i guess because the thermostat closed. if it is working properly.it is new but i have bought bad ones.? closed everything and started it up i got a few bubbles in the res. pretty much right away. after a few minutes the temp gauge was between 1/2 and 3/4 and it started gurgling and spitting hot water out of what does appear to a vent holeor blowouthole feature in the res. upper and lower rad hoses were both hot and the fans never came on. so what do you guys think could i have gotten a bad thermal switch and a bad thermostat. i dont know :oops:  

[chrissev]

Question:  how did you fill the system?  I'm wondering because sometimes if you fill it wrong you can get an air bubble in the bottom of the cooling system that won't allow any coolant flow.  To prevent this you always fill the system by removing the top hose from the radiator and filling through there until the coolant spills out, then reconnecting this hose to the radiator.  

Also, you might want to remove the hose that comes out the bottom of the top hose connection to the cylinder head at the front, and put a hose in that and see if you get flow out of the radiator.  You should.  If not then it might be blocked

[albsure]

welcome back i havn't seen you for a couple of days. i took the top hose off of the engine and filled through the rad. then took off the other end  from the rad. and filled to the block. also is the reservoir vented should it be spitting hot water from the res. should i plug the hole?? what are the chances of getting a bad thermal switch and thermostat. should i leave the parts stores alone and just go to the VW dealer and pay the price for oem parts??

[fspGTD]

The vent hole in the top of the spherical A2 and later expansion chamber vents out anything that gets by the pressure cap.  Your pressure cap should hold approx 20psi before it vents.

That much coolant getting spat out of the top could only be caused by: 1. overheating, boiling coolant, building up steam and pressure.  Listen for any boiling coolant, which might continue for a little while after shutting off the engine.  Could be caused by a bad thermostat, bad water pump, insufficiently filled system with air pocket impeding circulation, etc.

Or,  2.  a blown headgasket, letting pressurized gasses from the combustion chamber bleed into the cooling system while the engine is running.  You can check for this by right after a cold start, removing the pressure cap and sealing the hole with your hand and feeling for an immediate pressure build-up.  An immediate pressure build-up indicates a blown head gasket.