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VW Golf MK7 TDI - Heater blowing cold / Silicant bag in expansion tank

Posted By candellara Monday, June 24, 2019 8:55:51 AM
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VW Golf MK7 TDI - Heater blowing cold / Silicant bag in expansion tank...

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candellara
 Posted Monday, June 24, 2019 8:55:51 AM
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I posted this on an old thread relating to the same issue but someone suggested i post a new thread

As stated, 6 months ago (during a motorway drive) we lost heat to the vents and we had gurgling noises from the dash. The car was subsequently booked into VW and their diagnosis was that there are no fault codes present but what is common on MK7 Golfs was that the silica bag in the water expansion tank ruptures and blocks the heater matrix. Price to rectify £819 for new matrix.

I didn't believe them and was a bit miffed that they hadn't tried to flush the system so i took the car away. I disconnected the hoses from the matrix at home and flushed with a hose and water was flowing freely. Upon reconnecting & top up, heat from the vents again!! The car only does local town driving and everything has been well for 6 months UNTIL, a recent motorway drive. Same symptoms, no heat from vents, gurgling noise and some water being forced from expansion tank on this occasion. Note that the coolant in the system is totally clean along with the expansion tank - no signs of any dirty contaminated water.

After returning home, i ordered a new expansion bottle & cap - very low cost and really to eradicate these items from being any cause. After fitting and topping up, we have heat again from the vents.

Well, today i opened up the old expansion tank with a saw - and, the silicant bag is not ruptured and is fully intact with all of it's crystals!!!!! Now this is becoming farcical as the amount of threads there are all over the forums about this exact problem and VW continuing to replace heater matrix's. One poor lady has had 3 heater matrix's as the VW dealer insists that the silicant granules have contaminated the system and continue to block the new heater matrix's. Indeed my local VW dealer wanted to relieve me of £819 for replacing the matrix - when we now know the matrix isn't blocked.

Any thoughts?
Monday, June 24, 2019 8:57:17 AM by candellara
Crasher
 Posted Monday, June 24, 2019 5:35:16 PM
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The Golf 7 (MQB platform) heater matrix is extremely prone to getting blocked even when you are convinced it isn’t.

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laldog
 Posted Monday, June 24, 2019 6:20:47 PM
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So if your matrix is fine and the dealer is wrong what is wrong with your vehicle??
candellara
 Posted Tuesday, June 25, 2019 6:04:16 AM
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laldog (24/06/2019)
So if your matrix is fine and the dealer is wrong what is wrong with your vehicle??


I don't know but i'm not convinced it's a heater matrix issue as all incidences of this seem to surround either the silicant bag rupturing or brown stained coolant from casting sand remaining in blocks.

Currently the vehicle has no issues - but it's only being used for short journeys. The problem only happens during longer motorway runs and becomes apparent when there is no heat to vents, gurgling sound from dash and water leaking from the expansion tank. Under the bonnet, coolant pipe to matrix is hot - outlet pipe is cold.

Short runs / city driving no problem. Heat from vents, both pipes to matrix piping hot, no water loss or gurgling noises etc. Temp gauge always reads 90o and no fault codes present when the system was scanned by VW
Crasher
 Posted Tuesday, June 25, 2019 4:44:07 PM
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Ignore the temp gauge, the readings are a joke. We have replaced a large number of MQB platform heater cores now and not once have I seen one of these tea bag things, plastic cylinder yes but nothing else. The system MUST be flushed absolutely clean.


Vile Invention

Dark was that day when Diesel conceived his grim engine that begot you, vile invention, more vicious, more criminal than the camera even, metallic monstrosity, bale and bane of our culture, chief woe of our Commonweal. How dare the Law prohibit hashish and heroin yet license your use, who inflate all weak inferior egos? Their addicts only do harm to their own lives: you poison the lungs of the innocent, your din dithers the peaceful, and on choked roads hundreds must daily die by chance-medley. Nimble technicians, surely you should hang your heads in shame. Your wit works mighty wonders, has landed men on the Moon, replaced brains by computers, and can smithy a "smart" bomb. It is a crying scandal that you cannot take the time or be bothered to build us, what sanity knows we need, an odorless and noiseless staid little electric brougham.

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candellara
 Posted Wednesday, June 26, 2019 6:07:40 AM
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Crasher (25/06/2019)
Ignore the temp gauge, the readings are a joke. We have replaced a large number of MQB platform heater cores now and not once have I seen one of these tea bag things, plastic cylinder yes but nothing else. The system MUST be flushed absolutely clean.


Still not convinced. If the matrix was blocked - it would be a permanent issue rather than an intermittent one? Why would it be that in normal city / town use the car has no issues - both pipes to matrix hot and heater working fine, no coolant loss etc and then you go on a high speed / motorway drive for 30 minutes - this issue suddenly appears?

Where VW don't have a coolant flush as part of the service schedule - is it coagulation of the G13 coolant causing issues?
Wednesday, June 26, 2019 6:12:53 AM by candellara
McTech
 Posted Wednesday, June 26, 2019 7:22:00 AM
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Hi C,

It is possible that the issue is nothing to do with blockages in cooling system.

Could it be gas in the cooling system causing gurgling noise after 30 mins of the motorway.

e.g. egr cooler leaking under higher pressures, but yes we could expect increased temp at ECT

I don't know but maybe the heater matrix constricts when flow increases causing some cavitation

I'm not saying this is the case - but if your car was with me and the cooling system flows correctly I would be looking for other possiblities.

Then again Crasher has VAG tattooed on the inside of his eyelids - a vast amount of experience.

Just thinking aloud....

M


I O, I O, its off to work I go!
Trovs
 Posted Wednesday, June 26, 2019 3:29:58 PM
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Water pump?
candellara
 Posted Thursday, June 27, 2019 5:04:42 AM
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McTech (26/06/2019)
Hi C,

It is possible that the issue is nothing to do with blockages in cooling system.

Could it be gas in the cooling system causing gurgling noise after 30 mins of the motorway.

e.g. egr cooler leaking under higher pressures, but yes we could expect increased temp at ECT

I don't know but maybe the heater matrix constricts when flow increases causing some cavitation

I'm not saying this is the case - but if your car was with me and the cooling system flows correctly I would be looking for other possiblities.

Then again Crasher has VAG tattooed on the inside of his eyelids - a vast amount of experience.

Just thinking aloud....

M


It's a tough one and alot of head scratching but one thing's for sure - i don't want VW to start swapping out parts without a firm diagnosis - that's one of the reasons we pay VW £150 per hour rather than an independent garage. There are so many incidences of this across the web and some people report that even after a new heater matrix at a cost of over £800, the fault still exists. There must be a definitive answer to this issue where someone has a identified the problem and made a correct diagnosis
McTech
 Posted Thursday, June 27, 2019 5:00:37 PM
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Tests can be done to check for cavitation using a WPS on a scope.

EGR cooler can be tested pressure test fairly easily.

A quick gas test on cooling system.

Tests really need to be done when fault (going cold) occurs.

I would do all @ £50 and hour....BigGrin

£150 ph buys you "similar" but with a leather sofa to sit on - filter coffee and a copy of Hare and Hounds...

and you'll still get a new matrix

M


I O, I O, its off to work I go!
Thursday, June 27, 2019 5:02:06 PM by McTech

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