Bit of advice needed on plastic coolant flange replacement, HM engine

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VAG Fan
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Bit of advice needed on plastic coolant flange replacement, HM engine

Post by VAG Fan »

On our 1990 Fox, the plastic flange that sits on the side of cylinder head, pointing towards the left wheel (on top of the bell housing, i.e. at the exit point of the coolant) is leaking. I replaced the seal a few years ago, but I think the whole flange has now warped from the heat. It's leaking from the top bolt hole. So I'd like to replace the complete flange.

1) I've just phoned Goldwagen. The Aluminium flange is actually still available at R250. The plastic one is R60. Does anyone have recent experience with the quality of the plastic flange nowadays? If the quality is dodgy, I'd rather spend a bit more and have peace of mind. But if the plastic will last for a good few years, I'll take one...
2) This leak has been around for quite some time. The bolts may very well be rusted to the cylinder head. Any tips on removing them without shearing them off? E.g. preferably do the job on a cold or warm engine?
Mark R.
- - - - - - - - - -
2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
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Wolf Mk2 16V
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by Wolf Mk2 16V »

I bought the aluminium one, has to last longer
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panic-mechanic
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by panic-mechanic »

Alu one is always preferred
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by VAG Fan »

Thanks, gents, that settles it then.

Any words of wisdom on pre-emptive treatment of those bolts? I'd like to minimise the chance of complications, as I can only attend to the car over weekends and it needs to be kept running.

Even back in 1996, when I loosened those on my Mk1 GTS, the one bolt actually stripped and removed some of the alloy threads from inside the cylinder head. But at least the bolt didn't shear off. I could replace it with a longer one.
Mark R.
- - - - - - - - - -
2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by freezaburn »

I'd spray and soak with Q10 a few times and leave overnight to loosen any stubborn bolts...

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panic-mechanic
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by panic-mechanic »

And then I discovered shnell rostloser from liqui moly. Beats Q20 at that job.

https://products.liqui-moly.com/repair- ... t-xxl.html
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by VAG Fan »

Good stuff, thanks. I'll try to get some when I buy the flange.
I hope the Rostlöser gets past the wet flange holes and into the actual threads.

Much obliged for all the help!
Mark R.
- - - - - - - - - -
2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
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OettingerTDi
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by OettingerTDi »

I replaced the flange on the Citigolf a while ago, but with a plastic one, wasn't aware there was a aluminium one. So far so good.

Make sure to clean up the area on the head where the old flange comes off so you get a smooth surface. Then apply a thin layer of gasket sealer on the flange before you bolt it back to the head.
Anton van Graan

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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by VAG Fan »

Thanks, Anton.
I bought the aluminium flange from GW yesterday (R245, hopefully it should outlast the car...).
I don't actually have any form of gasket sealer (have always been relying on O-rings to do their job, but not always with 100% success). Any particular sealer you would recommend? (My Dad always spoke fondly of Hermetite Red, but I don't know whether that even still exists.)
[Edit: search function points mostly to Wynns gasket maker or similar; I'll ask at my local Midas or GW.]
Mark R.
- - - - - - - - - -
2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by OettingerTDi »

I used a gasket sealer I found at Midas, it was about R35-00. There are different heat ratings, I went for the one which was rated for up to 180 degrees C. My car is a 1300 and doesn't work that hard.
Anton van Graan

Current:
2009 Touareg 3.6 VR6
2007 Caddy Life 1.9 TDi
2004 Polo 1.6 Comfortline
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1997 Chico 1.3

Previous:
2003 Audi S4
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1998 Jetta 3 CLX (Taken by a friendly chap called Jack)
1993 Uno Turbo
1988 Ford Laser 1600i Sport
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by panic-mechanic »

grey sealant by elring/dirko. Buy it a Goldwagen. the end.

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VAG Fan
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by VAG Fan »

The repair is done. After seeing the old, warped plastic flange, I'm glad I bought the aluminium replacement. Granted, the OE part lasted for 27 years, but the cylinder head flanges are the hottest points of the cooling system, and somehow it goes against my grain to fit plastic there.

The bolts, BTW, were not severely rusted into the head.

For the first time in 30 years of motoring in Mk1s (sorry, Neuk and other purists), I had a real problem bleeding the cooling system. The engine wouldn't pull in the coolant but just kept boiling it out. But I managed eventually. Wonder whether the thermostat is going sticky.

Anyway, thanks for all the help.
Mark R.
- - - - - - - - - -
2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by panic-mechanic »

I have only had issues with bleeding those if you forget to open the hot water tap(switch the heater on) or if you close the cap pre-maturely. So let it idle with the heater on and the cap open till where it slowly starts pushing water up from heat( around 80degrees usually) then close the cap. Keep feeling for thermostat opening and watch the temp. Once thermo open wait for fans to run. Let it cool down, top up. Sorted.
Stephan van Tonder - Jhb - Putfontein Benoni
'05 Audi A6 3.0L TDI Avant
'09 Touareg 3l TDI
'13 VW CC 2l tdi (repair project)
'05 Touareg v10

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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by panic-mechanic »

I have only had issues with bleeding those if you forget to open the hot water tap(switch the heater on) or if you close the cap pre-maturely. So let it idle with the heater on and the cap open till where it slowly starts pushing water up from heat( around 80degrees usually) then close the cap. Keep feeling for thermostat opening and watch the temp. Once thermo open wait for fans to run. Let it cool down, top up. Sorted.
Stephan van Tonder - Jhb - Putfontein Benoni
'05 Audi A6 3.0L TDI Avant
'09 Touareg 3l TDI
'13 VW CC 2l tdi (repair project)
'05 Touareg v10

Perfect Power dealer. I do dyno tuning.
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Re: Bit of advice needed on plastic coolant flange replacement, HM engine

Post by VAG Fan »

Yup, closing the cap prematurely was my mistake. The heater valve was opened, so no problems there, but I had added too much coolant to the expansion tank too early, and so I thought I'd close it while warming up the engine, to prevent any unnecessary spillage, and just open it for short times. Wrong strategy. Took me twice as long, especially since the temp gauge itself (not the sensor) is iffy, meaning I had to guess the temperature somewhere in-between a cool lower radiator pipe and a boiling-back coolant feed pipe. So I ended up spilling a whole lot of coolant anyway. Learnt my lesson...
Mark R.
- - - - - - - - - -
2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
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