Please help me out with VW golf mk4 cooling issues

[Jimmyl]

Hi guys,

I have a 2003 VW golf mk4 1.6 L BFQ on the clock of 151 Kkm. It has been making issue after issue including sludges in engine oil fixed with flushing, bad idling improved by replacement of camshaft position sensor, malfunctioning O2 B1S1 needed renewing sensor... and the main issues currently are quite frustrating:

symptoms and signs- engine lights on, not smooth start, temperature climbing slowly, both fans on low to middle speed whenever igniting and lasting for a while after removing key. There is no overheating and after a while of driving, temp always reaching a stable 90 C. Now I have to take off the 30A first level fuse to stop the fans.

scan results: 1. 17700/P1292/F265 MAP controlled engine cooling thermostat circuit open, apparently normal cooling temperature sensor G62, with key on ignition, tested near 5 V between negative and positive pins, 0V between two pins of heating plug of Map controlled thermostat ( with temperature sensor G62 plug off). 2. 17811/P1403 EGR system : regulation divergence.

Plan: to fix engine code P1292, now I've ordered a Map controlled thermostat.

Request for help: please give me advice whether to also replace temp sensor G62 or further wiring check (with which I am not good at all). What do you think about the cause of constant fans-on? Is this associated with stat's problem?

Could any one help? Any advice of any is much appreciated.

Jimmy

[Jimmyl]

Update: I checked wiring of both temperature sensor and MAP controlled cooling thermostat. All normal. However I checked the resistance value of the heating component in MAP controlled cooling stat and it was open. So I put the new thermostat housing in, left the other parts of cooling housing untouched, replaced new red coolant, and deleted fault codes. Guess what, now both fans stop and temperature jumps to 90 C much faster. Rescanned again and there is no any fault code.

Therefore, P1292 code does influence over fans behaviors on VW Golf mk4 BFQ model. Many posts from various car forums say a stuck open thermostat won't cause both fans operating on cold start. My case shows that they are misguiding.

I did start to rule out issues related to FCM( fan control module) or radial thermo sensor and radial thermo switch, but luckily, I decided to try replacement of thermostat first and it works well. It saves me a lot of time and $$$.

Jimmy

[LeStig]

Great result !! These things can be difficult to diagnose ..... cooling fans have many issues !!

[Jimmyl]

Actually, before replacing the MAP controlled cooling thermostat, I had done many scans and noticed that whenever I deleted the bad codes, both fans did not engage at start but kicked in about 1-2 minutes later. I reckon it's about time that ECU receives fault info from the stat unit and thinks it needs to maximise the cooling in an effort to avoid engine damage. So that was my little theory but some mechanics firmly told me: no! I was told that having both fans on without AC on and at cold start has nothing to do with an opened stat, that I should take it as an additional issue other than stat.

Now a little bit happier but who knows. They say owning a VW means endless repairs! Of course ownership of a VW car either drains one's wallet or makes him a mechanic very soon.

[Jimmyl]

I mentioned the relation between fault codes and engagement and fans on cold start with AC off. The rationale behind this is, it's a functional issue instead of a physical problem. So try not to do any other replacement of parts for the fans running.

[flecralf]

Actually, before replacing the MAP controlled cooling thermostat, I had done many scans and noticed that whenever I deleted the bad codes, both fans did not engage at start but kicked in about 1-2 minutes later. I reckon it's about time that ECU receives fault info from the stat unit and thinks it needs to maximise the cooling in an effort to avoid engine damage. So that was my little theory but some mechanics firmly told me: no! I was told that having both fans on without AC on and at cold start has nothing to do with an opened stat, that I should take it as an additional issue other than stat.

Now a little bit happier but who knows. They say owning a VW means endless repairs! Of course ownership of a VW car either drains one's wallet or makes him a mechanic very soon.

Despite this old Threat...
Hey Jimmy,
you're right, after two Fiat (Panda Uno) and an Peugeot 309 confirm your point of view.
Before owning the damn Golf 4 I was limited focused on changing Brake Pads, Disks....exhaust system and similar fun stuff nothing critical....then came Drama Queen from Wolfsburg...Windscreen, Starting Issues....better Non-Starting-Issues....Cooling-Liquid-Fun on the street....electrical fun like magic automoving Windows...fear of the rain due water near the driverside....and an door left back, thats not supposed to be open cause of incoming water....and now top of list.... motortemperature is raising, engine is about explode...good idea to bring the car to ucraine border this days...at least in the role as decoy, drawing russian fire on it, would be my angry vendetta. Proud to be an German engineer. :-(
Best wishes
Ralf