Coolant blown out from expansion bottle

Thanks Shocks. I was reluctant to go to VW as it’s likely they will fit or sell me the same part which is obviously the cause of all our problems, but i’m no mechanic so I can’t dismantle and delve to far - I’ll break something else .

You don't have to buy the part from them but their electronic parts catalogue should have the correct type listed for your vehicle. If it's the one you linked to it'll be the same part number I mentioned.

By the way, the part VW supplied to me is a Rev B part, as designated by the B at the end of the Part number. The one I took out was a Rev A part so they've possibly addressed the defective design in the current unit.

@shocks that’s really useful, thank you again.

minu94 said:

So, this is the result after checking for exhaust gases in coolant. It’s pretty clear that it tested positive.
Before and after:
https://ibb.co/BgXpXmw
https://ibb.co/6YR8PK7

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Hi Minu94.
Did you have to change the headgasket?

Hi all,

yet another one experiencing this issue. 2014 golf mk7 GTD 73000 miles. Water pump and belt changed at 56000. Luke warm air from cabin vents on hi but nothing to shout about. Coolant loss which I can only presume is being pushed out of the expansion tank. Again needs refilling every 200-300 miles. Only one thing to add to it which i’d be curious to know if others have suffered is that the car will occasionally swing over for 3-5 seconds on start up. Could this potentially be related? Also interesting to note that I only realised that my vents weren’t acting as normal when my electric supplementary cabin heater failed on me and then I could see the true extent of my lack of heating.

I have the same symptoms. I took the car in November 2020. It was produced in 2015 at 176,000 km. Since I thought it was a lot of kilometers, I decided to serve it. We changed belts and water pump. The mechanic told me to monitor the antifreeze, but for the next month I had no problem. One morning when I turned it on, the low coolant light came on. I immediately called the mechanic and although he suspected there was air in the system, he told me to top up and drive. After about a month, the situation repeated itself. During a visit to the representative office, I was recommended to change the software due to the dieselgate problem, which made the regenerations more frequent. Which helped me find out that I always lose antifreeze after regeneration. So far I have changed the cap of the expansion vessel without success. I haven't noticed that it doesn't keep me warm in the winter. I found that the air conditioner was not blowing cold enough. The jet is colder on the left than on the right. Today I will check the air conditioner for loss of freon.

My engine is a CXXB. I have not met other colleagues here with this engine, but I guess the problem will be in the same part.

I noticed most in this thread are outside the US. My car has this problem as well. I have not taken it in to the dealer (yet) and just been topping off the expansion tank when it's low (haven't been driving much due to the pandemic). I also have no heat coming from passenger vent, and I believe blow out from expansion tank occurs during regen. I'm wondering if it's best to take it into the dealer and have them replace the heater matrix and flush the system, instead of them wasting time (& $$$) diagnosing the system?

--Ry

I’ve been monitoring this issue with mine after some great advice from people on this thread. I can 99% confirm that my blow outs only occur during regeneration. I can drive for days without any issues, but as soon as I notice the regen is taking place, sure enough there is a loss of coolant.

Shocks - you gave me some good advice about what part to change (which I intend to do shortly once I’m back in a familiar place) and how to manage on my forthcoming long journey. Im about to embark on said journey from Gibraltar to Scotland, I have 4 litres of the new pre-mixed G12 Evo coolant (which has replaced G13 and other variants), so I will report back on how the journey goes, how often the regen occurs and how much coolant I lose on average.

Since the last regeneration I have covered 412 km. The coolant level has not moved from MAX. Although the daily temperatures are high here, I decided to drive a little with the heating in HI mode. It seems to me that the flow is warm enough on both the left and the right side. There is another point that worries me. After buying the car, I gave it to replace the belt and water pump. Naturally, this involves draining the coolant. The change was performed in an unauthorized service center. A month later, the low light came on. I gave it to the still air in the system. After a while, I realized that this type of engine is bleeded in a very specific way. Is it possible that there is still air?

In two days I will go to the authorized service for inspection. What I want to know is that I have no problem with the head gasket.

On leaving my workplace, I felt that regeneration had begun. The revs went up to 1000 at idle and the fan turned on. From my workplace to home I have a drive of 50 km. and I thought it was the perfect time to test, I stopped at the first possible gas station and saw that my level was at Max. I continued my journey at a speed of 110 km / h on cruise control. Shortly before I arrived, I felt that the regeneration was completed according to the oil temperature readings (from 105 dropped to 91 degrees). As soon as I stopped in front of the house, I saw that the liquid level was at the MIN. The expansion bottle was not wet-walled, but I thought there was moisture at the bottom. 100% of the problem for me is only with DPF regeneration.

Yesterday I was at Volkswagen service center. They did a pressure test. The car keeps the pressure perfectly. They checked for external leaks and the operation of all pumps and the thermostat. For them, everything is normal. To further look for the problem, they want to dismantle the EGR and the intake manifold . I guess they won't find anything there either. Since the last regeneration I have passed no more than 100 km and the coolant level is still at MAX.

Travel about 200 km in two directions. On the way, everything was normal. I felt that the regeneration started in the city. I had a short drives and the regeneration could not be completed. But the level remained at MAX. The moment I got out on the highway home, the regeneration started again. I sensed it from the noise from the engine and the increased consumption on the dashboard. When I arrived I checked the level. It was already at the MIN. This morning I decided to hang two identical thermometers on the left and right vent nozzles. At a temperature set to HI and maximum fan power, the readings were 58 degrees Celsius on the left and 54 degrees Celsius on the right. Is this normal?

For May 25 I have scheduled disassembly and testing of EGR and intake manifold. I'm hesitant to tell them to change my heater matrix first.

deyan.akiwanov said:

For May 25 I have scheduled disassembly and testing of EGR and intake manifold. I'm hesitant to tell them to change my heater matrix first.

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Deyan, just my opinion, but I wouldn't bother with the EGR and Intake Manifold, based on the experiences of most here, it will end up being the Matrix. Also, if they do start changing out bits like these, you're looking at some big bucks!

deyan.akiwanov said:

At a temperature set to HI and maximum fan power, the readings were 58 degrees Celsius on the left and 54 degrees Celsius on the right. Is this normal?

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From memory, mine was a lot worse than this but I wouldn't rely completely on temperature differential to discount a restriction through the heater matrix.

I believe this is what happens when loss of coolant aligns with DPF Regen Cycles, If you look at a diagram of the cooling circuit (e.g., A19-11786 for my vehicle), the bulk of the coolant flow from the EGR cooler must pass through the matrix. Immediately after DPF regen, hotter than normal exhaust gets pushed through the EGR cooler. A restriction in the matrix, and therefore the coolant flow path (brown circuit), may cause the coolant to boil but the pressure/steam does have another path via the "small coolant circuit" (red circuit) to the expansion bottle. At the expansion bottle the cap works as designed by opening and dumps the excess pressure along with your coolant out of the car. There must be tipping point where the EGR coolant system breaks down because of the accumulation of crud in the heater matrix, hence the sudden onset of the problem.

shocks said:

MaximusDoom, I would strongly advise you to find a new mechanic. The magic tools he's referring to cost about a hundred quid and even though doing a head gasket repair is time consuming, it should be well within the ability of anyone claiming to be a mechanic. Any independent specialist VAG mechanic should be able to do any VAG repair without exception, even adaptations requiring factory authorizations.

I also wouldn't advise anyone to start with the assumption it's a blown head gasket. The very large majority of people on this forum have fixed their issues with a heater matrix change and this in my opinion should be the starting point for most people in the affected mileage/age range we have seen.

What sort of head gasket test did this "mechanic" do, a gas test isn't conclusive as I found out when I decided to change my head gasket out based on results of one of these tests. I did this head gasket replacement by myself by the way, and without having burglarize a dealership for tools as well mind. I found nothing wrong with the head gasket.

Unfortunately, I didn't discover this helpful thread until I was halfway through that exercise, after putting everything back together I was still getting blowouts of coolant. Once I changed that Matrix though, voilà, problem gone!

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Hi I have a 1.9 tdi 2008 I have this type air lock/build that results in back pressure into the coolant reservoir causing a loss of coolant gushing out the overflow when i undo the cap. when you say "Matrix" do you mean the heater matrix??

Any mention of Matrix on here is generally referring to the heater matrix. Note though, I think all the comments on here are w.r.t. EA288 engines which may or may not be relative to your issue which is related to an earlier generation diesel.

After the problem became more frequent and in my opinion started to happen and not only after regeneration, it was time for the diagnostics scheduled by the dealer. Dismantled the generation and somehow inflated with air. They said that I have a rather large loss of pressure in the intercooler. I found it at a price of about 400 euros. Changes are forthcoming and I will inform you about the result.

I own a 2013 registered Golf Mk 7 2.0 TDi Bluemotion. Low mileage-67,000 currently on the clock. Just recently it has had a history of coolant loss from the expansion bottle with no evidence of leaks or overheating, usually after a good run at main road/motorway speeds.. Both water pump and thermostat seals had already been replaced. Fault has now been identified as a defective ancillary water pump. Apparently the Mk 7 did away with an intercooler and two ancillary pumps do the job. A clue to this is also poor cabin heat performance. Now fixed to the tune of £240-the pump alone is £160. If you get any of these symptoms get your friendly garage to check them out in addition to the obvious.

There were visible traces of antifreeze on the intercooler. After changing it, I have already traveled 1000 km without the level drop. Engine dynamics have also improved.

markp66 said:

I own a 2013 registered Golf Mk 7 2.0 TDi Bluemotion. Low mileage-67,000 currently on the clock. Just recently it has had a history of coolant loss from the expansion bottle with no evidence of leaks or overheating, usually after a good run at main road/motorway speeds.. Both water pump and thermostat seals had already been replaced. Fault has now been identified as a defective ancillary water pump. Apparently the Mk 7 did away with an intercooler and two ancillary pumps do the job. A clue to this is also poor cabin heat performance. Now fixed to the tune of £240-the pump alone is £160. If you get any of these symptoms get your friendly garage to check them out in addition to the obvious.

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Can you identify the specific pump (and perhaps a part#) that failed on your car based on the cooling system diagrams shown in this recent tdiclub post? Cooling System Loops

Hi all, hope this thread is still live. Have the same coolant loss problem on my 14 plate Golf mk7 GTD so I’m looking to change the heater matrix.
I’m confident I can do the trim removal to get to the core (sat nav, glove box etc). My question is (to those who have already gone down this path): Did you clamp off the heater hoses in the engine bay and disconnect them at the bulkhead? This is what it says in the vw manual. Or did you just clamp the hoses and catch the coolant as you disconnected at the heater matrix?
Many thanks for any advice.

GTD64 said:

Hi all, hope this thread is still live. Have the same coolant loss problem on my 14 plate Golf mk7 GTD so I’m looking to change the heater matrix.
I’m confident I can do the trim removal to get to the core (sat nav, glove box etc). My question is (to those who have already gone down this path): Did you clamp off the heater hoses in the engine bay and disconnect them at the bulkhead? This is what it says in the vw manual. Or did you just clamp the hoses and catch the coolant as you disconnected at the heater matrix?
Many thanks for any advice.

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Hi, from memory the service manual says to clamp at the bulkhead (engine side hoses), disconnect at the bulkhead connectors, and then clear the matrix and interior lines by using compressed air. Make sure to put a bottle or container over the second opening to catch the coolant.

I would not recommend trying to catch the fluid in the car, the pipes are in an awkward place and you're going to make a mistake or miscalculation and end up with the inside of the car stinking of coolant for ever. There's a fair amount of coolant in that circuit and this is the reason the procedure is written the way it is.

shocks said:

Hi, from memory the service manual says to clamp at the bulkhead (engine side hoses), disconnect at the bulkhead connectors, and then clear the matrix and interior lines by using compressed air. Make sure to put a bottle or container over the second opening to catch the coolant.

I would not recommend trying to catch the fluid in the car, the pipes are in an awkward place and you're going to make a mistake or miscalculation and end up with the inside of the car stinking of coolant for ever. There's a fair amount of coolant in that circuit and this is the reason the procedure is written the way it is.

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Thanks for the advice Shocks. The reason I was exploring this option was that the bulkhead connections are a bit tricky to get at without removing some other bits first. Also best not to disturb connections that have been in place for a few years unless absolutely necessary.

Hey all,
great thread going here for this issue. I recently took my car to get cambelt+waterpump changed and get my 'no heat from vents' checked
no coolant leak was found external and CO2 test was done and came out green color. no leaks from water pump and both pipes hot from matrix. no error codes from computer
mechanic says coolant is burning internal possible internal blow needs further investigation however this particular garage dont do engine work.
is this likely to be head gasket related or still possibility of other issues

cambelt or pump werent changed in the end

bigb said:

Sorry no help here but has anyone noticed all these cars are from the general areas of England, Spain and Australia?

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That's interesting. Do you think there is a manufacturing defect? The climates are quite different. There must be as lot of people with this problem when you think only a tiny fraction of them will end up on this forum. I have a theory for others to blow apart. Let's imagine the defect is the headbolts fractionally too long or that they blow there thread out and let gases from the combustion chamber go down the head bolts and into a cooling passage. Another thing I was thinking about is the so-called parking heater. This small electric pump runs for a short time after the engine is turned off in order to heat up water in the heater circuit by taking the heat from the cylinder head.

How do we ever solve this if even the dealers don't know what it is? Would it be true to say there isn't generally anyone in a modern dealership that knows anything in depth about the cars they sell; they only know what VAG might have taught them at some training seminar. But think about what these people do. They are part fitters. They are stuck following procedures in a manufacturer workshop manual. They may not even understand how an EGR cooler can cause your engine to hydrolock.

I sympathize with all of you dealing with various cooling system problems. No, I mean really sympathize, because I have had my own, and still do!

1. When my sunroof drain failed, causing overflow to drain through the A-pillar, soaking the wiring bundle(s) directly under it (with connectors right there!). Dash lights/warning signals went crazy when I started it. I ended up taking it to the dealership BEFORE the recall issued on the FAULTY sunroof drains. They charged me just under $900 to fix it. Within less than one year, the recall went out, but despite numerous attempts to get reimbursed, TOTALLY ignored by VW (by mail, and twice electronically-WITH DATED RECEIPTS).

2. While the dealer had it, I walked back into the shop, and the tech had the dash COMPLETELY removed, because diagnostics were telling him that the DEF heater module (among other things) was failing. WRONG, he eventually figured out it was actually the soaked wiring, but when he reassembled the dashboard, HE BROKE THE HEAT Temperature control, or did not connect it properly. It was early Summer, and by the time I needed heat, and realized he broke it, it was 5 months later! No service warranty. Skrewd.

So I have no heat. BUT WAIT, this gets more amazing...

3. I then experience failure to warm up (engine). In the cold weather, it seemed like the thermostat was stuck open. I could see the gauge begin to climb, then plummet repetitively. I endured the cold without heat, couldn't defrost the windshield, and had to drive with frosted foggy windshield!!!

4. Oh, but then into the next mid-Summer, the water pump began to leak at the center of it-bearing/seal causing coolant to spew on the outer rim of the pulley. This water pump replacement costs just as much labor as a timing belt job (minus the relatively inexpensive timing belt parts). And I needed a new pump anyway, so I had reputable TDI guru in Belton MO do a timing belt job (as long as he had to open it UP!!!).
This was at ~70,000 miles!

5. Oh, and the thermostat is totally buried under the new location of the intercooler, with ridiculously complex plastic housing to remove, so that cost an additional ~$200, mostly labor. Did it all at once with TB replacement.

6. But I keep smelling coolant, and guess what... within a month, reservoir needed topping off. I don't drive it much now

I still have no heat. Guru replaced the failure prone clutched water pump with a normal pump, so it warms up (very slowly), but the heat control knob is STILL not connected. It gets warmer in the cab when I take a right turn, then cools off on left turns. OMG

I miss my 2014 TDI wagon with a clutch. Oh yeah, I have a DSG service kit and just can't wait to do that... Wonderful. I am at 75,000 now. I am driving my Toyota truck since it is getting cold again. What a steaming (OK, wheezing coolant) pile.

vwmk7 said:

Hey all,
great thread going here for this issue. I recently took my car to get cambelt+waterpump changed and get my 'no heat from vents' checked
no coolant leak was found external and CO2 test was done and came out green color. no leaks from water pump and both pipes hot from matrix. no error codes from computer
mechanic says coolant is burning internal possible internal blow needs further investigation however this particular garage dont do engine work.
is this likely to be head gasket related or still possibility of other issues

cambelt or pump werent changed in the end

Screenshot 2021-10-14 215134.jpg

• vwmk7
• Oct 14, 2021

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UPDATE
if anyone is interested or perhaps will help someone else experiencing this problem.

I have had the EGR cooler + heater matrix replaced both genuine parts
mechanic did the flushing 4 times and as well as the bleeding
now the heating is ok and gets warm before temp hits 90.

I bought my GSW with 97000 miles, and no heat. Dealer said the TSB says to flush multiple times, and that’s what takes up most of the labor costs. Silica gel pack was burst. Gurgling coming from heater core area. Whole shebang. I have plenty of distilled water and G13, and have a new heater core ready to install. I also got the coolant flush solvent from VW to put that through just in case. Unfortunately we just had a blizzard so I’ll have to freeze my feet off for a bit (no garage so it’ll have to wait) before I do it all.

Ive been looking at different methods to flush, and trying to find the best way. I’ve seen one where you use a wet/dry shop vac on the expansion tank to suck the coolant out (disconnect a hose on the battery side to let air in and modulate the vacuum), one where you let gravity work by disconnecting hoses on the bottom of the vehicle, and one that’s a combo of those two. What have you all tried, and what do you recommend?

mom picking up the Venturi type vacuum system to do the refill, and will probably do the refill(s) that way.

THANK YOU tdi club for this thread.!!!

I bought my Son his first car. VW golf 2013 Highline 2.0 TDi Bluemotion second hand as a private sale. After his first longer drive on the freeway he pulled up to his mates house for a couple of hours and when he got back in he got the low coolant warning. He couldn't see any obvious leaks so he topped up with distilled water. Used the car again around town for the weekend and we kept checking the fluid levels which was ok. A week or so later the coolant dropped again much like all the others in the forum. ( at this stage I hadn't found this forum thread unfortunately) I took the car to the local mechanic to do a pressure test on the cooling system - perfect - no drop. Car ran again for another week and it did the same thing. I took the car to a specialist Audi service center (non Audi). They checked the car over and pressure tested it again. They had it for a week and it didn't have a blow out. At this time my son found this forum and we read almost every page. Over the weekend I emailed the mechanic and pointed them to this forum and suggested the Heater matrix is the likely cause. I spoke to them on Monday morning when they opened and they were un-convinced and suggested the problem was the EGR cooler. I disagreed with them and asked them to do a back-flush of the heater matrix and entire cooling system. They did this as requested and I picked up the car a day later. ( $330 later)
Of course a couple of days later the same Blow out occurred. I was convinced (95%) that the heater matrix was partially blocked. I ordered a new heater matrix from the local Radiator repair place ( about $300). Saturday morning I installed it ( followed the YouTube video above). Eventually got the matrix out of the car and of course the new part I had was the wrong size and part number for my car, and the shop was now closed for the weekend! Had to re install the old Matrix because I was away for work the next week and my son need his car.

So the following weekend I had the correct heater matrix for the car in my hand. Removed the old heater matrix for the second time ( only took 1 hr the second time) and installed the new one.

Before installing new one I compared the flow by blowing with my mouth through the matrix. The new one was completely un-restricted. When I blew through the original one there was significant back pressure and the was a lot of water gurgling sounds coming from within. I cut the end off the old unit later and I could see many of the cores were blocked up. 100% - this was definitely the fault. Some of the guys here on the forum point to the DPF regeneration as the trigger for the Blow out - 100% this was the same for me.

My Son has since done over 1000km and there has been no coolant blow outs since. We had to do a tiny top up after the first run as the air was still bleeding or from the new Matrix.

I could have easily been sucked into replacing the ERG cooler and spending $1000's more without a solution.

Thanks again for everyone's contributions!