Coolant/heater Mystery

[pcdee]

Hi all,

 

My heating is only blowing cold or luke warm at best and i've been trying to fix it for too long!

 

The latest twist is that after a coolant change something weird is happening to the coolant system. It's up to the maximum line, then SOMETIMES when I go for a drive the low coolant warning sounds and flashes. I look under the bonnet and the expansion tank is empty, if I open the cap the pressure gets released and the coolant comes flooding back and once it's cooled and settled down goes back to the maximum line.

 

So it appears I'm not losing coolant but it's going somewhere?! I've read and read as much as I can online and it all seems to point to an airlock which makes sense considering the heating problem and that fact that I put around 6 litres of coolant mix (G13 and ionised water) despite Halfords telling me it has an 8 litre capacity?

 

So could there be a 2 litre air lock?! It doesn't seem likely?

 

Do I have a cracked block?

 

The head gasket seems fine - no mayo in oil, no oil in coolant.

 

I've driven the car to temperature, parked back up and taken of the expansion tank cap (as it's supposed to be a self bleeding system), squeezed all the pipes and idled for ages but nothing seems to have happened. Is there a bleed valve?

 

The other thing i've noticed is the higher right hand side hose (looking at the car head on) going into (?) the radiator is hot but the lower left hand side hose coming out (?) of the radiator isn't as hot - don't know if that means anything?

 

It'll cost me a fortune to take it the local Skoda dealer but i'm running out of ideas........ 

Edited 13 November, 2014 by pcdee

[steveo82]

Is yours a diesel engine? If so then yes they are a big old cooling system!

 

If the coolant capacity is indeed 8 litres then yes this could cause an airlock as from empty to max line in the expansion bottle is about 3/4 litre to a 1 litre so there's still a litre to go before it's full!

 

The system needs to be topped right up in the expansion tank then engine run up to temperature and you just keep an eye on the tank and top up, usually when the thermostat opens it will drop, this is when all the air will be forced out of the system and then top up as required. There are no bleed valves on these engines to my knowledge so I would do as described above and see how you get on.

 

As long as it gets up to temp then the stat sounds like it's working and the hose situation you describe sounds like an airlock to me.

 

Steve

Edited 13 November, 2014 by steveo82

[Guest]

I've found on problem cases like this I've needed to orient the car at some extreme angles to purge any air, such as finding the steepest incline, grass banks included!

Get the car facing skyward and give the throttle a good few blips, reverse to change the angle and repeat.

Crazy but it has worked for me before.

[pcdee]

Cheers guys i'm off to find a hill!

[mixskoda]

I'd hate to say it but you may have a very slight leak on your head gasket allowing air bubbles to enter your cooling system which then find the highest point - usually the heater matrix. the coolant level dropping in the expansion bottle is due to the rubber hoses expanding due to the increased pressure, and when you release the cap and the pressure with it, the hoses relax again and the coolant rises back up the bottle. I hope I'm wrong but its been a tell tale sign for me in the past and turned out to be right in the end. I knew on earlier skoda,s that if the cam belt and water pump had been changed with pattern parts, some times the water pump impellers would come away from the shaft causing no water circulation. Has yours been changed ??

[pcdee]

Thanks for all that mixskoda.....

 

So after Halfords told me the cooling system (on a 2005 2.0l Tdi Octavia estate) has a capacity of 8 litres I checked with skoda and they confirmed that to be true. I felt relieved because I got less than 6 litres in when I did the coolant drain/flush/clean/refill so this will certainly be a contributing factor. Seems obvious now but that's why when under pressure, the coolant disappeared - I was around 2 litres short.

 

Just bought a third bottle of G13 and topped it up (used 4 litres in the end). Waiting for it to cool down again to hopefully squeeze in some more water for a near 50/50 mix.

 

I bought the car (used obviously) a couple of months ago and the cam belt and water pump was changed as part of the deal. So you could be on to something.... 

 

What do you mean by pattern parts? Is there a way to check?

There is coolant circulating (can see it trickling back into the expansion tank when up to temp) is that what you mean by water circulation?

 

Is there was even a slight leak on the head, would an exhaust gas test on the coolant show this up? Or does it need to be big leak to show up?

 

I've currently got the dash off to access the matrix. Even before I topped the coolant up, both metal pipes (inside of the bulk head) connecting to the matrix are red hot but the matrix itself (inside the plastic cover) isn't hot which to me makes no sense? How can the inlet and outlet pipe be hot but the bit in between not? That must be the issue with the heating right - matrix not hot = air flowing over it not hot?

 

We're closing in now! Continued thanks for everyones help.

Edited 14 November, 2014 by pcdee

[pcdee]

(just had a google for pattern parts. I understand now. The garage that carried out the cam belt/pump change put a stamp in the log book so i'll check in with them).

[trundlenut]

Are you sure you got 8 litres out when you drained it. When I did the cambelt and water pump on my old Octavia, there was about 1.5L still in the system after taking the pump off and draining the system.

Sent from my Nexus 4 using Tapatalk

[pcdee]

Hmm good point. I can't tell what if any was left in the system. Where would it hide after a drain? The matrix?

[trundlenut]

Hmm good point. I can't tell what if any was left in the system. Where would it hide after a drain? The matrix?

Depends on where you drained it from.

Sent from my Nexus 4 using Tapatalk

[pcdee]

I disconnected the outlet hose from the radiator (bottom left looking at the car head on) and then disconnected the top right hose to radiator after a while too. Idled engine for a bit until the expansion tank was empty and low coolant alarm sounded then flushed with water. Reconnected hoses and put a bottle of cleaner and water through the system. Disconnected hoses and flushed again with water as before then reconnected everything and put new water and coolant back in. (Car was cold when all this was done)

Edited 14 November, 2014 by pcdee

[mixskoda]

An exhaust gas check would show traces in the coolant but as you've just changed it, it may take a while. If the coolant is trickling back to the expansion bottle then the coolant is flowing fine as you said. The cooling system should bleed itself normally, that's the idea of the small return pipe. If both heater pipes are hot then that usually means that the coolant is circulating through the heater matrix. If the car was older I would have suggested flushing out the matrix in both directions using some rubber hose attached to a hose pipe but a mk2 Octavia isn't that old, unless the car had some head issues before you bought it which churned up some muck from the water jackets in the engine and settled in the heater matrix. What mileage is the car ? Is the heater control working ok ? On a different thought, I purchased my parents mk2 2.0 tdi with only 39000 on the clock but it was already on its second radiator as we were told from the vw specialist garage that fitted it, that its a common fault that they start leaking from the bottom corner. Could that be your coolant loss ? Is your car petrol or diesel ?

[pcdee]

It's a 2005 2.0.Tdi and it's done just over 131,000. 

 

Even though both matrix pipes are hot could the matrix still be blocked? I don't know the coolant system layout but I wonder if the matrix part of the circuit (suggesting the matrix can't be blocked) or if it is 'tee'd' off so the inlet pipe is can get hot, the matrix is blocked but the outlet pipe gets back filled by the coolant system so that gets hot too? I think I'm going to have to go for a matrix change. They're not that expensive and it'll rule it out once and for all. 

 

The controls seems to work fine and with the left hand side dash off I can see the heat flap arms move when I change the heat setting.

[mixskoda]

^{I would try and flush it out first as changing the matrix is not a 5 minute job, and the air con pipes would need to be disconnected which would mean a re-gas - if you have air-con that is, also if the heater pipes have already been off in the past have they been put back on the right way ?}

[pcdee]

No air con but i'll give the matrix flush a go. Space is really tight on the Octavia - can barely get a hand in to touch the pipes with a finger tip (engine side). How to get in and disconnect matrix pipes - remove under tray and get underneath?

[Guest]

This should help:

http://skoda.workshop-manuals.com/

[pcdee]

nice one! http://workshop-manuals.com/skoda/octavia-mk2/heating_ventilation_air_conditioning_system/heating_air_conditioning/heating/removing_and_installing_parts_of_the_heater_unit_part_3/removing_and_installing_heat_exchanger/

[mixskoda]

Any luck with the heater ?

[brizer]

Hi pcdee I had the very same problem with mine, it all started when my water pump gave up the ghost & got a friend to change for me then the problem started & like you spent a lot of time trying to bleed it. then decided to take it to a skoda dealer to sort it out, they said it would mean the removal of the new pump as I could not guarantee it was a genuine part (it wasn't) plus he put it in with mastic & this clogged up the egr valve. that was that problem solved but my heater still does not work just blows cold air until I put my foot down then it blows hot but goes cold again. so if you sort heater out I would be great full to find out. all the best Gerry. 

[Guest]

@brizer

Assuming some mastic has found its way into the heating circuit, it's plausible that it's acting like a flap valve, or at least a restriction.

High rpm will increase the flow of coolant to the point that there's sufficient heat going into the matrix but as your engine speed reduces so does the flow of hot coolant and the demand for heat overcomes the supply so you get a cold output.

A new matrix may be the only solution or you could try flushing the current one out.

[brizer]

Hi Micmac. Thanks for that info I was sort of going down that road, now I will have to find my Haynes manual & find out where to start bet its a bloody pain to do. no good asking the dealership as they said they didn't have a clue what it could be, but their happy they have my money for the work they have done, (I,m not bitter)

     will give it a go when I get the chance & some nice weather. Thanks again Micmac all the best Gerry. 

[Guest]

@brizer

Don't forget the links previously posted in this thread, they'll help more than your Haynes manual... they're just not the same these days

[brizer]

Hint taken thanks again :beer: Gerry.

[pcdee]

Hi,

 

Sorry for taking so long to get back.

 

The problem has gotten worse in that now the car is actually losing coolant. Haven't had time to engage with it properly over the last few days but a block tester (http://www.ebay.co.uk/itm/181059430832?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT) is on the way and so is a new coolant cap to make a pressure tester. I plan to drill a hole in the top of it and put a bicycle inner tub valve through and seal with silicone sealant, fit the cap, and pressurise the systems up to 15 psi with a bicycle track pump and watch for a drop in pressure/see liquid coming from a hold in a coolant pipe.

 

I've also got a new matrix on the way (part no.1K0819031B) - mine was £22 used and delivered on eBay.

 

So I plant to test for exhaust gases in the coolant and hopefully that's not the case. I'll also change the matrix to get rid of that variable. Then pressure test the system and try and find any leaks.

 

I'm hoping that the matrix is clogged and there's a hole in an easy to get to pipe! 

 

Will update with my findings.

 

(any best practice tips for exhaust gas testing and/or pressure testing very welcome)

[VrsMule]

Is it over heating at all ? The Mrs had an A3 1.9 TDi and it was overheating intermittantly and bringing on the coolant low level warning, changed the thermostat still the same and the heater was non existatant after that. Turned out to be a tiny nick in the head gasket.