Hey all

I just finished installing a new radiator instead of a really leaky and clogged one, which probably also had tap water in it, and also flushing the rest of the system with a garden hose. Then I replaced the generic coolant to a G12+ equivalent.

While in the past the temperature never budged from 90C, on the first long drive I've noticed it goes down to 80C and 70C at 100kmh even with the AC (and the fan) off. Going downhill even gets it to 60C! Ambient temperature was around 20C. I never though it was possible. Going uphill however brings it to exactly 90C like in the past (and maybe in traffic lights as well, we'll see).

Is it a new issue? Or is the new radiator (made by Nissens) and the G12+ coolant (made by Liqui Moly) are that good that the temperature cannot go up with the 100kmh windflow? What would happen when ambient temperatures would be around freezing?

 

And another thing: as mentioned, after the replacement, with the pipes disconnected from the radiator I took out the thermostat, cleaned it, and rinsed the pipes with a water hose (like Hanes recommended), filled a G12+ coolant, and replaced the thermostat. The problem is that only 4 liters out of the 5.6 capacity entered the system. Plus now there seems to be a mix between the old green liquid and the new red one in the tank along with foam as in the picture. What's your opinion?

Could be the combination of your new radiator working a lot better and your thermostat being shot. When the thermostat spring gets too worn it will allow coolant in the radiator at too low temperatures, cooling the engine too much/too soon. It could well be that your old radiator countered this.

 

It could also be that there are air bubbles in your coolant system, which give a bad temperature reading. Some hard steering to the right and left while driving can help make the bubbles float up. 

 

Don't know about the foam you are having.  maybe try flushing it some more times

Thank you. Can I take out the thermostat again and check it somehow? And can I take it out without losing a lot of still good coolant?

Is the temperature reading from one place? Because I am constantly checking mid-drive and the fan is off until it reaches the correct 90+ C as in the manual. It only happened when I idled for more than 10 minutes after filling up the coolant - I wanted to check that the fan logic is still correct and operating, and it is. For me it was clue that the sensor for the fan and the sensor for the gauge agree on the coolant temparture.

Edited 9 March, 20215 yr by PIXIP

Did you have heater controls set to hot when flushing with clean water?

 

There's a heater core that warms the cab. Perhaps that still had old coolant mixture in. Should be G12. Maybe someone used Ethylene Glycol (blue or green) not G12.

 

G12 and G12+ mix fine.

 

Mixing pink G12+ (OAT) and green/blue Ethylene Glycol coolant can turn to jelly. That might be the foam. Doesn't look like oily mayo of head gasket.

 

If bubbles present the temp sensor will read wrong.

 

Perhaps you can drain, reverse flush Radiator on its own and Block and heater together and try again.

 

Edited 9 March, 20215 yr by dvderlm

I don't have a manual covering AEE so I can't answer about thermostat/fan wiring switches.

 

On 2000 to 2002 Polo the heater core matrix is not accessible without aircon system disruption and needs VW dealer help.

 

You could perhaps use an IR thermometer to measure top and bottom radiator hoses as car warms from cold until the thermostat opens and hot coolant flows through rad, and the fan comes on.

 

Thermostats are cheap, get lazy and sticky staying open, so engine runs too cool.

 

There's also a weak spot in the plastic bridge of the housing...

 

Looks like you haven’t got rid of all the old coolant and it’s reacted with the new G12 stuff, turning it to a foam.
 

Unfortunately, to rectify this you’ll have to bite the bullet and completely drain the system to get rid of it all. The mix will be lurking in the heater matrix, engine block, radiator, expansion tank and pipes. Just draining the rad won’t be enough to get rid of it. 
 

You’ll need the hosepipe again to flush it all out. It’s also best to do this with the thermostat out and ‘ back flush’ the engine.

 

You need the rad pipes off to flush the rad and engine properly.

 

As mentioned, you need the heater set to full heat setting,otherwise coolant will be trapped in the matrix. You  then need to flush through that too. You need to do this until the water runs completely clear. The  longer you flush the better result you’ll get. 

 

As for the temperature it’s running at, to dispel any thermostat issues and to check it’s opening and closing ok at the correct temperature, you can stick it in a pan of water and boil it gently to check it opens/closes ok. If you have a thermometer that reads to 100deg C even better, the thermostat should begin to open around 80/90 deg, Though I’m not sure of the actual figure, though it can be stamped on the thermostat.

Edited 9 March, 20215 yr by mk2tastic

certainly needs that mess flushing out , wont be a problem to flush and refill with water , go for a drive and repeat until its coming out clean 

 

trouble is that doesnt explain the over cooling ...i wonder is the new thermostat stuck open?  i had this on another car and the car wouldnt get up to temp however hard i tried 

I'd bet on it being a stuck thermostat - I hat the exact same symptoms (minus the foam!) and a new thermostat fixed it. 70C on the motorway and then it would get warm in traffic or basically whenever air wasn't rushing through the radiator. Either a dodgy wax piston in the thermostat or something in the thermostat housing is clogging it open - either way looks like you need a good old flushing again anyway!

alot of non genuine thermostats are trouble , nearly scrapped our other car due to trusting a new one was working , after lots of head scratching a genuine one made it run fine 

 

your local parts store most likley has some additive to help clean the coolant   

The thermostat opening temperature specs can vary depending on engine size, whether it’s petrol/diesel and even the country the vehicle in used in, so if it does turn out to be the stat, then make sure you get the right one for your engine.

you can test it at home if you have a thermometer 

 

should be closed when cold then warm in a saucepan , it should open at the temp shown on the side of the part or the box , then close again as it cools 

Thank all!

Apparently the heating doesn't work at all! I don't think it is related to the radiator job I've done. I haven't used the heating anyway for the last 1.5 years, so wouldn't been able to spot the problem before the coolant change. In any case, there's cold air coming out now from the cabin vents, even on full heat.

Guess I need to figure out what's wrong with the heater matrix before I could flush the pipeline again like many of you recommended. I'll do that before trying to changing the thermostat since I believe it is still working.

 

As for the numbers:

Edited 13 March, 20215 yr by PIXIP

Only cold air comes out of the lower vents, (on the dash facing you,) warm air only from the long vent by the windscreen. 

Try and get a coolant flush from Halfords, euro, gsf, whoever is near you. Follow the instructions on the bottle. Make sure you donk around with heater controls to get it in and around the heater matrix. 

If there is still any old coolant anywhere in the system, unfortunately it means your new coolant will be contaminated. Not a problem if the old and new coolant are the same, but it will cause issues if they are different. 

As said above, before adding coolant, it wouldn't hurt to fill system with water only and run it up to temp or even drive for a day to flush system as much as possible, just make sure you play with the heater controls to get it all in the heater matrix. If you can spring for a couple of coolant flushes, adding a second if you run it in just water may help clear more too. 

Because the heater matrix is higher up in relation to the rest of the cooling system, and also has spots old coolant can hide, gravity is kind of against you on that one. 

Good luck dude. 

 

Thank you for the tips! I will try but honestly I can't tell if it's hot air or not yet. I'll have to wait for a cold night or something

 

The old coolant was a generic green one. The new one that was flushed, is a red Liqui-Moly G12+. I guess there was some mixing since foam started to show up in the overflow reservoir. I did take the thermostat out when I replaced the radiator and flushed the engine coolant pipes with a garden hose. Wouldn't running the engine on normal water cause rust and such?

 

Also, I have a coolant flush ready from Prestone. I also have this how-to video on safely flushing the heater matrix, which I am debating whether I should try: https://www.youtube.com/watch?v=M9SIafVsqyc

 

 

The air that comes out of the dash vents facing you will be "cold" or a bit colder than ambient. The air that comes out of the upper dash, runs along bottom of windscreen and also down onto your feet, or out the sides of the centre console if you have one, should feel noticeably warm compared to the front dash vents.

 

I had issues with my cooling system leaking last year. Turned out to be metal pipe running along the back of the engine into the water pump Had rusted through. 

As i had to replace that pipe, the bottom hose and also one of the pipes connected to the heater matrix, mine was pretty well drained. I did flush out as much as possible. Any pipe i could get the hose into, got flushed!!

 

When you put the flush in, go for a drive, set your heater controls to max and put them on full blast. That will pump the flush all around the system and up through the heater matrix. You could put the flush in a day, maybe even 2 days before you're looking to drain and flush, but you don't HAVE to do that.

 

Leave the heater controls on max setting while you drain and flush too. Once you've flushed and drained, you could fill up with just water again, and run it up to temp with heater on full blast just to be sure. If there's ANYTHING left, you'll see it come out when you drain again. Scuzz will hide like you wouldn't believe up in that heater matrix! Once you're confident it's all been cleared, fill her up proper. 

I filled up with prestone coolant last year and it's worked fine for me. 

 

Coolant/antifreeze has anti corrosion additives to help keep rust at bay inside the pipes. Doesn't help the outsides if you live anywhere with salty sea air! 

Good luck.