[1.6 FSI] - Headgasket or simply Trigger's Broom

Evripidis said:
@PlasticMac I have a spare tank that I can pressurise and a vacuum pump with a set of ac gauges to test cap. I'll waste my time fitting the brand new polo one instead though as it will prove quicker. Most of my hoses are custom made so maybe there is a slight orifice somewhere that only leaks under vacuum.
Click to expand...
I'm not 100% sure of my theory, but pulling a vacuum directly on the expansion tank, (with the cap off), on the car, will tell you if there's a vacuum leak anywhere on the system. It's not unknown for a hose to spigot joint to be fine under pressure, but leak under vacuum.

The one way valve idea may be nonsense, and the system is sealed, with only over pressure relief. The small amount of air in the tank may just get compressed when the system is hot, and returns to ambient once it's cooled.
Mac.
 
Guys, I have know at least a couple of times, the expansion tank cap failing to close correctly, therefor letting air in.
 
Good Evening Evros,

Although probably not needed by now some FSI coolant warmup figures. I fear it will be of little use anyway, read on but thought i would post it anyway.

Background.

Ambient temperature 12℃ by dashboard gauge.
Climate ON and set to 23℃, working under AUTO.
Slight breeze that maybe added a minor cooling factor on the engine.
Engine cold at start and car largely stationary but it did include a brief gentle run of a few hundred metres at the start. (My neighbours windows are only about 4 metres from my parking area and she also chose today to hang out a great pile of washing. Thought best not to annoy by not having a running engine for half an hour and moved to the car park at the local rec, had the car park to myself.)

To begin some very subjective measurements by eye from the dashboard temperature gauge.

Time since engine start
(mins.)		Temperature
(℃)
14.5Needle moves off 60℃
17.570
21.980
27.990


As you can see it took almost half an hour to reach its normal (intransigent) 90℃ and it s becoming clear I made a big mistake in turning on the climate but I did not want to get cold!

What VCDS is showing at this point.

VCDS Coolant Groups.jpg


I logged the groups and spent a long time this evening grappling with Excel and a 2000 line worksheet, knowing little about how to use Excel. I eventually got Excel to produce some summary results. The real data…


Time since engine start
(mins.)		Coolant temperature at engine outlet
(G62)		Coolant temperature at radiator outlet
(G83)
Mins.℃℃
0.0912
1.01612
2.02712
3.03612
4.04112
5.04512
6.04812
7.05112
8.05312
9.05412
10.05612
11.05713
12.05813
13.06013
14.06113
15.06313
16.06514
17.06614
18.06814
19.06914
20.07114
21.07214
22.07315
23.07415
24.07515
25.07715
26.07815
27.07815
28.08016
29.08116
30.08216
31.08416
32.08416


Interesting to note the pronounced bend in the graph at about 6 minutes. My guess is that is when the cabin climate opens its flaps and begins to seriously use the coolant heat, severely slowing the coolant warmup.

It was clear it was going to take a long time to reach 110℃ so I gave up and called it a day. I am minded to do this again and leave the cabin climate off, but it will not be before Thursday.



Andy
 
@Andrew Andy I cannot find a way of thanking you enough. Thank you for doing this.

For the record, I began fitting the new tank yesterday but the mounting points need some modification to fit.

So, your test results are the same as mine give or take. The ambient temperature was the same and it took about the same time to reach 80 degrees. Of course I helped it out by doing a couple of short runs. When I did my first test run I had the cap of which helped in warming up and overflowing. During my second row of tests I had the cap on and got the results that you have read.

From what VCDS could tell me, I could see a perfectly functioning control of the system. The thermostat element started heating up when the engine outlet became hot enough and then let go when it cooled down. Then the radiator bottom hose began getting warmer. If it became too warm then it fired up the fan and so on and so forth.

After the sniffng test and the vcds tests, the header tank is the only thing left. After that I am not sure what else there is to do.
 
Andrew said:
Good Evening Evros,

Although probably not needed by now some FSI coolant warmup figures. I fear it will be of little use anyway, read on but thought i would post it anyway.

Background.

Ambient temperature 12℃ by dashboard gauge.
Climate ON and set to 23℃, working under AUTO.
Slight breeze that maybe added a minor cooling factor on the engine.
Engine cold at start and car largely stationary but it did include a brief gentle run of a few hundred metres at the start. (My neighbours windows are only about 4 metres from my parking area and she also chose today to hang out a great pile of washing. Thought best not to annoy by not having a running engine for half an hour and moved to the car park at the local rec, had the car park to myself.)

To begin some very subjective measurements by eye from the dashboard temperature gauge.

Time since engine start
(mins.)		Temperature
(℃)
14.5Needle moves off 60℃
17.570
21.980
27.990


As you can see it took almost half an hour to reach its normal (intransigent) 90℃ and it s becoming clear I made a big mistake in turning on the climate but I did not want to get cold!

What VCDS is showing at this point.

View attachment 104892

I logged the groups and spent a long time this evening grappling with Excel and a 2000 line worksheet, knowing little about how to use Excel. I eventually got Excel to produce some summary results. The real data…


Time since engine start
(mins.)		Coolant temperature at engine outlet
(G62)		Coolant temperature at radiator outlet
(G83)
Mins.℃℃
0.0912
1.01612
2.02712
3.03612
4.04112
5.04512
6.04812
7.05112
8.05312
9.05412
10.05612
11.05713
12.05813
13.06013
14.06113
15.06313
16.06514
17.06614
18.06814
19.06914
20.07114
21.07214
22.07315
23.07415
24.07515
25.07715
26.07815
27.07815
28.08016
29.08116
30.08216
31.08416
32.08416


Interesting to note the pronounced bend in the graph at about 6 minutes. My guess is that is when the cabin climate opens its flaps and begins to seriously use the coolant heat, severely slowing the coolant warmup.

It was clear it was going to take a long time to reach 110℃ so I gave up and called it a day. I am minded to do this again and leave the cabin climate off, but it will not be before Thursday.



Andy
Click to expand...
Andy,
If you set the climate to OFF, the engine, well the dashboard gauge rises to 90 in a few minutes. That's because the cylinder head, oil cooler, heater matrix coolant circuit looses the heater matrix, so almost no heat loss. I think, for the test to be typical, the climate should remain ON. That "small circuit" as Audi call it is quite effective, when the heater matrix is in circuit.
Mac.
 
Just realised I lost the fruits of my struggle with Excel, a 'graph', and the comment about bend in the curve out of context in last night's post.

Should have included

"
1676983325613.png


Interesting to note the pronounced bend in the graph at about 6 minutes. My guess is that is when the cabin climate opens its flaps and begins to seriously use the coolant heat, severely slowing the coolant warmup."

Andy
 
Andrew said:
Just realised I lost the fruits of my struggle with Excel, a 'graph', and the comment about bend in the curve out of context in last night's post.

Should have included

"
View attachment 104907

Interesting to note the pronounced bend in the graph at about 6 minutes. My guess is that is when the cabin climate opens its flaps and begins to seriously use the coolant heat, severely slowing the coolant warmup."

Andy
Click to expand...
I'll take a look through the HVAC label file, it may confirm your guess, at what point in the warm up cycle the HVAC controller decides to open the heater flap.
Mac.
 
@Andrew Yes indeed, I stand corrected. Looking at numbers all day I knew what you meant bend in the graph. Your experiment is the same as mine, it take a while to warm up.

I'll put it on the road for a couple of days and see what happens. When replacing the header tank, interestingly enough, the internal tank skin could move on the new one but was solid on the old one (and on an even older one).
 
Evripidis said:
@Andrew Yes indeed, I stand corrected. Looking at numbers all day I knew what you meant bend in the graph. Your experiment is the same as mine, it take a while to warm up.

I'll put it on the road for a couple of days and see what happens. When replacing the header tank, interestingly enough, the internal tank skin could move on the new one but was solid on the old one (and on an even older one).
Click to expand...
The time taken to warm up, and the seemingly low level of cooling required, tends to confirm the high thermal efficiency that the FSI was designed to achieve.
Mac.
 
PlasticMac said:
The time taken to warm up, and the seemingly low level of cooling required, tends to confirm the high thermal efficiency that the FSI was designed to achieve.
Mac.
Click to expand...
I admire your romanticism Mac. Mine has been leaking for quite some time now. Like the coolant.
 
OK,

The new expansion tank has been holding up fine. The old one must have failed either internally or at the sealing surface where it meets the cap. There has been no overflow or any signs of it, but.....

The radiator is leaking. It is weeping from the right-hand side and loosing coolant. It is less than 6 years old but I suppose it has had it, especially given the abuse it has taken.

Does anyone know of a reliable or OEM aftermarket brand?

Regards,
Evros
 
Evripidis said:
OK,

The new expansion tank has been holding up fine. The old one must have failed either internally or at the sealing surface where it meets the cap. There has been no overflow or any signs of it, but.....

The radiator is leaking. It is weeping from the right-hand side and loosing coolant. It is less than 6 years old but I suppose it has had it, especially given the abuse it has taken.

Does anyone know of a reliable or OEM aftermarket brand?

Regards,
Evros
Click to expand...
Good News Finally, my money would be on the Cap itself.
 
@Ami The cap is also brand new. I'd ordered 3-4 the last time.

The radiator had been showing signs but very-very minor. Now that the system is is holding up pressure, it is showing a lot more prominently.

I am not sure what makes I can get over here or whether I have to do another parts order from autodoc, which is a pain because I have to get the ordered delivered to Greece and then forwarded to Cyprus. A real pain.
 
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