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1.6 Bluemotion TDI Overheating

mikky

New member
Hello all at Golfmk6.com... first post so I hope this is in the correct forum, apologies if not.

I've joined up today to see if I can reach out to you MK6 guys and ask for some advice on an overheating issue I've been having.
Hopefully you guys might be able to help offer a cause.


Around town, the coolant gauge seems to stay at 90deg, although the fan is constantly blowing.
On the motorway at 70mph the coolant stays around the 90deg mark until going uphill when it climbs, but on the flat it can waver up too.
Turn on the cabin heater and the coolant temp rises very quickly, even when not pushing uphill, and has been up near 130deg when I've pulled over to let it cool.
Turn the heater off and will eventually cool, albeit very slowly.
Heater is hot.



Scenario is as follows:

2009 Golf Mk6 1.6 Bluemotion SE TDI


Last service done at 120K miles in Jan '21 - belts, water pump etc by my trusted local mechanic.
Last month (April) noticed that the coolant gauge was indicating high on the daily motorway commute - 120deg.

Went back into the garage for:

New thermostat - no change
New radiator - no change
Water pump fitted in Jan replaced - no change
Thermostat again - no change

Radiator is not getting hot (old or new one) - I can't feel the lower hose due to the undertray but the top hose is cold, as is the rad.
Water pump is flowing coolant back into the reservoir
Coolant has been bled a few times and is at pressure
No loss of coolant, nor any contamination
No emulsified oil
No loss of power
Cabin heater is blowing hot
Mpg is a bit low at 45
Oil temp is about 125deg
No warning lights, No rough running
Fan is always running very high
(It's had the dieselgate 'fix')

Upper/right hand hose going to the heater matrix is very hot, but cold on the return hose.

If the heater matrix is blocked, surely it can't affect the cooling system so much that it stops flow to the rad??


Could overheating be the matrix ?
If not the matrix what on earth is going on ??? I've run out of places to look.


I'm completely stumped!



Really hope you guys can shed some light on this.

Many thanks in advance.
 
Last edited:

vdubnick

Drag Racing Champion
sounds like blocked radiator... have you used g12 or g13 coolant only?
 

mikky

New member
Hope this helps anyone else who experiences this...
Bypassed the matrix and no overheating !
Radiator is now getting hot and all seems good.

I'm amazed the matrix can affect the cooling so much !
 

vdubnick

Drag Racing Champion
so, clogged matrix?
 
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