Mk4 GTI coolant loss

[Breadroll]

Just change the damn thermostat.

Whats that?

An a serious note listen to master Panic.

[watusay]

Oh God Bread...Hahahah send me one this way #thermostatplox

Yes Panic will do !!! Hehe

[watusay]

Just change the damn thermostat.

So Update...

Changed the Thermostat and its housing and also changed the thermoswitch on the Radiator as mine was looking a bit fugly when I changed the radiator (a while back)

Okay so update.

Cold Start. Car gets to 90 degrees and takes forever for thermostat to open, like a good 7 mins at 90 but when they do the fans come on gently and temp never rises. Take her out for a drive and bring her back and now temps are definitly behaving and the fans do come on. So looking pretty good so far.

Coolant level dropped a bit but I did flush a lot of it out so just wanted to ask hows do I bleed the system?

Also the old thermoswitch had an oring on it and the new one didnt come with a washer or oring, so reused the old Oring but it tends to squash a bit when your torque and when it does that it leaks a little. Is it supposed to have an oring on there or should it be a washer?

[watusay]

So car still loses just the tiniest amount of coolant but its very very little now.
Everything works well and fans come on when they should.

However I had a little bit of a rough idle on startup for the first 15 seconds and thught it was cause I did the N249 delete.

I decided to check the spark plugs. Theres a bit of oil on the tips of the coil pack and spark plug 3 and 4 needed a bit of effort to unthread(even after cracking I couldnt loosen with my fingers and had to use the ratchet). Also first 3 plugs coverd in oil the 4th was clean. Dont think its the valve cover gasket. I changed it 6 months ago and the spark plug wells seem dry, there seems to be another seal a bit lower down that looks like oil could be coming from there...Pics show nicely...Advice plese

[panic-mechanic]

There is only one seal and that is the tappet cover. There is not a second level seal. Often when a plug was not tightened properly it will carbon on the thread and be hard to undo.
When you reuse a water seal use silicone sealer and run a bead into the hollow of the fitting, Then push the seal into the silicone so it pushes out and then flatten that with your finger and install. No leak.

[watusay]

There is only one seal and that is the tappet cover. There is not a second level seal. Often when a plug was not tightened properly it will carbon on the thread and be hard to undo.
When you reuse a water seal use silicone sealer and run a bead into the hollow of the fitting, Then push the seal into the silicone so it pushes out and then flatten that with your finger and install. No leak.

Thanks Panic....I guess I need to redo my Tappet Gasket. I know I had the sparks torqued

[watusay]

And after a few days of working perfectly, after a spirited drive today she did the same thing...Fans didnt kick in until 105. Why I dont understand, thermostat is working as both hoses are hot but still. Coolant doesnt seem to be going down much if at all, puzzled as it was working.

[panic-mechanic]

Starting to think you have a waterpump issue.
Yes I know you say it was changed.

[watusay]

You sure waterpump and not cylinder head gasket? Bloody confusing as this was working perfectly. Not a hiccup and after a nice hard drive today with no time to cool down..straight into the driveway and idled and it started acting up. Shouldn't the fans kick in without it being water pump as it works off temp?

I changed timing belt and tensioner like 8k km ago as the mount near it had a loose bolt that kinda slowly rubbed against the belt. Would it be necessary for me to buy a new belt and tensioner if I change the water pump ?

[panic-mechanic]

of course I am not sure. Can't do diagnostic on the car itself. I have to depend on what you say. can't see the actual temp, can't feel a pipe, can't bypass switches, can't measure voltage nothing so no can't be sure.

[watusay]

This is where temp sits at when fans kick in but much louder than they were when they work at 90 degrees.
Top Rad hose much hotter than the bottom rad hose(which is hot but not boiling like top).
No VCDS errors

What else can I look for or test?

[dcmk4]

Of course one hose will be cooler given the fact that water coming out of a radiator is cooled..
If it's a problematic when sitting for a while then its water flow, either waterpump or thermostat.

Why not just change both and be done with the issues..

The fans are triggered by the temperature sensor on the radiator as far as I am aware, if there's not enough flow of hot water going through the radiator then the fans wont switch on as you are experiencing..

[watusay]

I changed the thermostat a few days ago and everything was working fine. Today it started to do it's nonsense again.

Would it be safe to say my fan control module is okay(when I on the A.C. both fans kick in)

[panic-mechanic]

No it is not safe to say the control,unit is ok. You have to test it with the thermo switch to see that at that stage it is either getting the right signal but not kicking the fans on high or is not getting the right signal.

[VAG Fan]

This is where temp sits at when fans kick in but much louder than they were when they work at 90 degrees.
Top Rad hose much hotter than the bottom rad hose(which is hot but not boiling like top).
No VCDS errors

What else can I look for or test?

In addition to Panic's last post:

From the above, I deduce that the high-speed mode of the fans is working, but the low-speed is apparently not. I would wager that either the thermo-switch (which you recently replaced) is faulty, or the fan control unit, or perhaps some part of the wiring in-between, or a fuse.

[TDIFlava]

Check if you water hoses are harder than normal or even swollen up when the car is running if it is then it should be an indication of a blown head gasket. Is there any coolant leaks that you can see as you mentioned the small loss of water?

[watusay]

Or or or. Can just make sure the bloody 30A fuse is not shot ....
Swooped with the ABS fuse...immediately threw ABS warning on Dash and the fans are now working. Stays around 96degrees in VCDS and fans kick in at 98.

Now u make sure no coolant loss.
My rad hoses feel full but not getting hard or like its swollen.

Water pump seems to be doing it's job as someone told me to also remove the small top coolant hose to check the flow and it's steady not erratic.

When they did the 3minute pressure test at the Silverton place here(not such a great place) it didn't seem to lose pressure at all.

The seems to be a very very light milkiness in oil cap but that's when I started the car. Let it warm up a bit but don't drive and checked. But as soon as I drive even that's gone. No milkiness on dipstick. Also some water out the tail pipe on first startup of the day.

Dunno if any of the info helps but yeah...always check thise darn fuses

[Ashveer03]

Check if you water hoses are harder than normal or even swollen up when the car is running if it is then it should be an indication of a blown head gasket. Is there any coolant leaks that you can see as you mentioned the small loss of water?

How does a hard/swollen hose indicate a blown gasket? I dont see how thats possible or even if it is possible thats a bad way of telling a blown gasket because hoses can deteriorate over time


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[VAG Fan]

How does a hard/swollen hose indicate a blown gasket?

Because the combustion gas, if it leaks into the cooling system, adds undue pressure.

[Ashveer03]

How does a hard/swollen hose indicate a blown gasket?

Because the combustion gas, if it leaks into the cooling system, adds undue pressure.

Oh ok cool i get your point, i still think thats not a very good indication of a bad head gasket..

Took OP a month of convincing to get the thermostat replaced, will need more convincing of how a swollen or hard rubber hose would 100% indicate a bad gasket.
@OP no disrepect, pointless replacing stuff thats not faulty


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[Stompie]

Could be wrong but im sure someone on this forum told me that the cooling system hoses will be hard when hot due to the pressure.

[watusay]

How does a hard/swollen hose indicate a blown gasket?

Because the combustion gas, if it leaks into the cooling system, adds undue pressure.

Oh ok cool i get your point, i still think thats not a very good indication of a bad head gasket..

Took OP a month of convincing to get the thermostat replaced, will need more convincing of how a swollen or hard rubber hose would 100% indicate a bad gasket.
@OP no disrepect, pointless replacing stuff thats not faulty

OP took a month because it wasn't really the thermostat was it. Both rad pipes got hot eventually. It was a case of the fan not spinning. More likely fixes were the Thermoswitch and the fuse. I tested the old thermostat mind you. Wasn't that old and it worked.

Don't think it's head gasket. Something would have contaminated by now. Car would run poorly. Something. For now I'm happy everything is working as is and will check the coolant but honestly. Doesn't look like its losing . Before it lost a lot.

By the way...I want to also burp the coolant system just for good measure. What's the best way if doing this as I've read many different ways

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[panic-mechanic]

There is 1 bar of pressure in the cooling system when it is hot. Anything more will get blown off by the water cap. Not a good indication of a blown gasket. If they immediately go hard even when cold - sure.
I did not even go to fuses in the check list because heck that is always the very first thing anybody checks isn't it?

[watusay]

True Panic bit I hate electrical system. Always sucked at wiring. Guy checked fuses from the top and said they were lekker. When I took it out saw it was looking rather old. The fact that I popped it in the ABS fuse and the lights popped up confirmed it.

Thanks though you were pretty spot on with most of the info. And I learnt something new

[watusay]

So update, cars temp is behaving 100% now no issues with that or the fans or anything.

Still losing a slight amount of coolant, from the max to the min mark every 5days.

My oil cap looks like this when I start the car, after a drive you cant see it but when you start it and just let it sit for a few mins and switch off it looks like this. Could this be a sign of head gasket?


However what I do notice is a bit of smoke(maybe vapour from where the Turbo Inlet pipe is and it doesnt seem to smell of oil but more like water as the smoke only comes out after the car starts for about a minute and disappears just as fast and happens everyday