Radiator air locks and overheating

Guys hopefully someone can answer this

My car has always suffered with getting hot quickly and the fan not kicking in.
I decided to drop the coolant out today and flush the system and start again.

Its a 1.8 DX GTI (capacity 6.3l)

I will add that the waterpump and thermo were all replaced less than 100miles ago.

Anyway dropped coolant from bottom radiator hose and there didn't seem to be a huge amount to be honest and ran 10l of water from the expansion straight out the bottom.

Bottom hose back up and with a 5l mix of 2l coolant and 3l water started to add approx 2l back in through the expansion tank.

Started the car and proceeded to get the other 5l in, around 1l later the return hose is squirting the mix back into the tank.

I decided to try to undo the upper rad hose to let any air out and it spat out what looked like 2l of filthy water.

Anyway I persisted with what I had and got the remainder of the 5l in the tank, the return hose returning the mix the entire time.

Heaters are on full blast and the top hose is very hot, bottom hose stone cold.
Squeezing the bottom hose did cause a bit of slashing around in the expansion tank and hose seemed to harded up a bit but it didnt get hot.

Left the car on idle for around 15mins and the water temperature gauge didnt go any further than halfway so there was never a cause for the fan to come on anyway but something tells me that it wouldn't of.

There is probably only around 3l of coolant / water mix in the system and I cant get anymore in if I wanted but car is behaving (on the driveway at least)

My question is how the hell do I get these air blocks out of my rad when filling it and should all the rad hoses be equal in temperature? ?

Well the easiest way to remove the dreaded air bubble is
to drill a 1/8 or 1/16 inch hole in the lip of the t-stat.



Shows the proper orientation of it installed in the housing as well.

When filling the system take the upper radiator hose off both ends with the hole drilled or not.

Fill the Radiator with the hose attached on the upper radiator fill until it trickles out the upper radiator

Reverse the hose to fill to the block side until it dribbles out.

Fill from the hose to the engine side and burp it a few times (heater matrix full hot). Fill until it dribbles out the hose end.

Reconnect the hoses and tighten the clamps.

Now add coolant in to the expansion jug about 1/2 of the Expansion jug.
Burp the upper hose 3 or 4 times.
Refill the expansion jug to 1/2 full.

Start the car and allow it to fully heat the system so the radiator fan cycles one time Burping the hoses as it warms…..

After the t-stat starts to open the air trapped should release and lower the expansion tank, so you may have to keep it at 1/2 3/4 full.

After the fan has cycled the second time, you shoudl be able to top the expansion jug to the Full mark, and Cap it.

All should be good to go.

Caveats.

Using the proper t-stat for the Radiator fan switch is a must.  I have seen folks use a 165 t-stat with a 195 radiator fan switch and the radiator fan never switches on to keep the radiator cool, and what is mistaken for a "Air Bubble isn't."

A radiator hose that is hot at the top, and not at the bottom indicates to me that the t-stat is bad.

Yes I have gotten new t-stats that were bad out of the box, I usually test all of mine in boiling water on the stove to see them actually pop open.

Yes I have gotten new Radiator switches that failed to close at the proper temp… So I test those as well with a pan of boiling water, a thermometer, and a DVOM.

As I said the easiest way is to drill the hole.

Now to add to your Dilemma.

When you break the connection on the radiator (lower) you will only get the fluid out of the Radiator to drain and a partial head drain, as well as possibly the heater matrix and the expansion jug.  Why because the cold t-stat is closed and will not drain the block.

You have to remove the t-stat cover and pop the t-stat out to get most of the engine and head coolant out.

When doing this now it the time that you reconnect the t-stat cover with out the t-stat. Reconnect and tighten the hose clamps on the outlets.

Remove the upper radiator hose both ends, and Flush fresh water into the radiator from the upper hose connection till it spews out the upper block flange, and it runs clean.

You will reverse the hose to the upper engine flange and Force clear water into it from the upper engine flange until the water coming out of the radiator upper hose is clean.

You do this a few times as I usually will do it 4 or 5 cycles, till I am sure that all the Crud is Flushed out.
You can use a radiator flush and run it about in your engine for a few hours to scrub it… then Flush and back flush…..

While I have the front unbuttoned I do the heater core separately.

I remove the upper and lower hoses off the Barbed connection as well as the heater valve.  I use a pair of hose pinch pliers on the lower hose.  I pour some Vinegar, or CLR in to the upper hose about a cup, and let it work for 30 minutes to 45 minutes.

I open the lower pinched hose and Direct that water on to the ground away from things.
I then flush the lower matrix hose so water is coming out the upper valve hose clear and clean.
Reverse the process, and fill or flush from the upper hose out the bottom, I do this a few times 3-4-or 5.

I replace the hoses and clamps then I know that the Matrix is clean and clear as I button up the front, and get ready to fill the system with new coolant.

I also know that I can if I want change over from the Oldy Green Prestone a/f to the Pink or orange as the system has totally been purged…

As a side note, you won't believe how much more heat you will get out of your heater now. 

As in all the years of driving Diesels and Gassers You can rightly burn your buns off….when everything is proper and clean.

Briano1234 please dont ever sell your Mk1 and leave this forum, I'd be lost.

Thats the most comprehensive answer I could ever of wished for, thank you

WATERNAIR said

Briano1234 please dont ever sell your Mk1 and leave this forum, I'd be lost.

Thats the most comprehensive answer I could ever of wished for, thank you

Not that complete, I forgot the part that after flushing the cooling system, to replace the t-stat and o-ring before filling the system…ohohOPppsie     I suppose I could of directed you to my pictorial how-do I flush and back flush my radiator thread link in the Archive section.

How-to-flush-your radiator | Volkswagen Owners Club Forum

Or it could be a bad water pump that had the plastic impeller crack and is freespinning on the drive shaft…..
which is why I never use plastic impellers ever.
 

As an extra bit of advice when flushing a crudded up  system DON"T do it on a new block driveway, I just know this………

Well not unless the wife is away long enough for the clean up.

Does it actually over heat and boil up/loose water.

There have been quite a few where people are thinking they have problems when its working OK. The engine gets hot before the rad, the fan usually only operates on hot days in traffic or doing 5 point turns.

TBigJohn said

As an extra bit of advice when flushing a crudded up  system DON"T do it on a new block driveway, I just know this………

Well not unless the wife is away long enough for the clean up.

That is what they make pressure washers for… and remember what goes on the driveway stays on the driveway….. and who needs a clean driveway anyway….

Briano1234 said

TBigJohn said

As an extra bit of advice when flushing a crudded up  system DON"T do it on a new block driveway, I just know this………

Well not unless the wife is away long enough for the clean up.

That is what they make pressure washers for… and remember what goes on the driveway stays on the driveway….. and who needs a clean driveway anyway….

I'm married to a psycho Geordie, a pressure washer wont suture my testicles back on!!

I guess it is what they say, "Tain't who wears the pants in the family, but who wears the panties."

Besides if you power washed a message in your mess then leave it for a few days,,,,, she will forgive you…..and oh, may turn out better than you think.

Early-1800 said

Does it actually over heat and boil up/loose water.

There have been quite a few where people are thinking they have problems when its working OK. The engine gets hot before the rad, the fan usually only operates on hot days in traffic or doing 5 point turns.

It boiled over during its mot after being on idle for over 30mins causing the tester to do a little dance underneath it, since then I haven't let it go that far.

I panic as soon as the needle goes in line with the warning led and pull over and turn it off, usually after thinking I've let it cool down enough it refuses to start (which isnt unusual for a hot old car) but it proves its getting warm enough to warrant the fan coming on

Normal operation of the temp gauge is that it should go between the led and no more than 3/4 at 3/4 the fan should engage…. leads me to say the fan switch is possibly wonky, but your other hot cold hoses aren't and that suggest the waterpump or t-stat.


Bad t-stat, Bad Fan switch, bad fan.
Jumper the fan to the battery and ground to rule that out.

How old is your waterpump?
Does it have a plastic impeller?

Mismatch between the t-stat and the radiator fan?
 

Remove the 2 wires that go to the switch located in the side of rad. Touch them together, the fan should run. If it does the switch is fkd, if not either the fan or the wiring is duff.

Both waterpump and thermo are less than 100miles old but no idea of what material the impeller is made from.

First thing will be to check that the thermo 1. Works and 2. Is right for the fan and after that put the hole in it once I know its good.

I'll test the fan and then try the system again

While you have it drained, check the fan switch as well.

Ok guy, processes of elimination.

Fan works when jumped to battery at motor (its topran which suggests its already been replaced )



I removed the fan loom and checked for continuity with the multimeter and no issues there despite looking tatty



Now at the risk of sounding thick, are these the two wires I am supposed to be bridging to make the fan spin?



Because when I do I get nothing

Refitted all and tried again.

All rad hoses are now getting equally hot and I can hear the coolant tank bubbling away, temp gauge is sitting here



I assume this should be hot enough to kick in?

Fan still not coming on, would it come on earlier if the wires were switched to low speed rather than high or should it not matter.

Does it sound like we are looking at the fan switch?

Yup the fan would definitely come on earlier if you had it on the low fan setting as it's a two stage system I believe.

Looks like someone has installed a single speed fan rather than a two speed and has butchered the wiring to fit it.

Try the switcheroo of the wires

Ian

Indeed they have, I dont think you can get hold of single speed fans anymore.

I seem to remember a friend of mine recently with an 83 driver couldn't get a 2 pin fan and had to make do with a 3 pin, 2 speed fan

Ok I'll try again on the lower speed (although given the choice I'd rather have it on the faster option if I can)

And if there is still no action I need to check both the thermoswitch and thermostat and make sure they are in compatible working temps.

You can do that.

Just take the lower temp side of the switch (radiator switch has 3 pins for a 2 speed fan and a single speed fan has but 2 pins), and wire the Low temp switch side to the high speed side of the fan.

The radiator fan switch has 12V to it on one side only when not picked or hot, as it gets hot it picks and puts 12V to the Fan, if it is three speed fan switch the fan will kick on high when the A/C is turned on, or when the temp gets to 105 depends on the switches rating.

Look up the a/c schematics and you will see
the 2 radiator fan switch temps.

In the earlier Rabbits/Golfs they used the same switch as the after-fan run.  Where on later Cabriolets /Golfs  they had a separate after run fan switch.