VW Golf Mk4 1.8 - Overheating

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Thu 21 Aug 2014 15:03
VW Golf Mk4 1.8 - Overheating - mscott

Warms up to 90 deg as normal and stays there for a few miles, then temp starts to creep up. Can be brought back down to 90 having the heater on full blast. Cooling fans not cutting in because the radiator is cold, but the top hose to the radiator is hot. New water pump 6 months ago. Any ideas welcome.

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Thu 21 Aug 2014 15:30
VW Golf Mk4 1.8 - Overheating - Railroad.
Even if the fans were cutting in they wouldn't have any effect on engine cooling since there's no heat in the radiator to be dissipated. The thermostat on your car is located in the return to the block from the radiator bottom hose. Change this anyway, whether you suspect it to be faulty or not, but if it was stuck closed it would give the symptoms you describe.

Edited by Railroad. on 21/08/2014 at 15:31

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Thu 21 Aug 2014 15:34
VW Golf Mk4 1.8 - Overheating - skidpan

Air in the system that was not correctly bled out when the pump was changed.

Radiator silted up and will not allow passage of water.

Would not suspect the stat since the top hose has hot water but they are cheap so worth changing anyway.

So basically I suggest you flush the system, change the stat, refil with water/antifreeze mix, bleed correctly and then see if there is an improvement.

FYI the fan switch on every VAG car I have owned has been 1/2 way down the rad. If the rad is cold the fan will never switch on.

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Thu 21 Aug 2014 15:53
VW Golf Mk4 1.8 - Overheating - Railroad.

Would not suspect the stat since the top hose has hot water but they are cheap so worth changing anyway.

I would agree with that if the thermostat was located in the flow to the radiator, but it isn't. it's in the return to the block.

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Thu 21 Aug 2014 16:38
VW Golf Mk4 1.8 - Overheating - skidpan

Would not suspect the stat since the top hose has hot water but they are cheap so worth changing anyway.

I would agree with that if the thermostat was located in the flow to the radiator, but it isn't. it's in the return to the block.

Thats changed since the 1.8 Mk 2 In fact every car I have owned has had the stat in the top hose close to the head, that way it gets hot water immediately form the engine. How on earth does the hot water get to stat in the block return to open the stat?

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Fri 22 Aug 2014 11:28
VW Golf Mk4 1.8 - Overheating - Railroad.
The wax end of the thermostat is always fitted towards the hottest part which in the case of it being in the return would be the block and not the hose. Also most thermostats are two stage, recognisable by the circular disc at the bottom. This opens and closes a bypass port which allows for coolant to actually circulate when the engine is cool rather than just remain still which is what tends to happen with single stage thermostats because the coolant has nowhere to go until it opens. This prevents 'hotspots' from forming at the furthest point from water pump and provides more even cooling.

Edited by Railroad. on 22/08/2014 at 11:32

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Fri 22 Aug 2014 14:03
VW Golf Mk4 1.8 - Overheating - dieselnut

I have the 2l CR diesel in my Passat & noticed the thermostat is the same, located in the return from the rad.

So it would seem VW have implemented this fundamental change posibly throughout its engine range.

Have other manufacturers done the same?

I'm guessing it must give tighter control over the engine temperature.

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Wed 27 Aug 2014 15:43
VW Golf Mk4 1.8 - Overheating - mscott

It was the thermostat.

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Wed 27 Aug 2014 17:24
VW Golf Mk4 1.8 - Overheating - Railroad.
Glad you sorted it and thanks for the feedback.
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Tue 21 Jul 2020 21:12
VW Golf Mk4 1.8 - Overheating - klejdi

Hello i have a mk4 gti 1.8 and it get overheation after 20 min that i start the car... i have change thermostat ... head gasket.... cylinder head... water pump... i have check radiator and the tubes if is anything wrong and again the same.... my golf is gazoline and with natyral gas. Pls if anyone have any idea please tell me. My instagram id klejdi_reci if u want to contact me

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