Porsche Enthusiasts Club Forum

OK so this was the post for the Porsche Show at Hatton

Scrub the Boxster, it won't be going
Fuelled up today & took it for a wash & whilst in the queue it boiled over big time. When the AA guy got to it, it had cooled & he topped it up with plain water. Nothing leaked out so we started it up. As it was warming through the penny dropped. As I had the hood down I'd turned off the climate. This switched off the fans which run all the time when the climate is on. It looks like the fans aren't tripping in when it gets hot, hence boiling over! So it'll be off next week to have the problem sorted, the coolant changed & it may as well have its service.
So it'll be Jeep tomorrow as the 944 needs a few jobs done before I'd take it that far.

A question for Jon M, what triggers the fans on is it just a water temp sensor somewhere or is it from the ECU?

Well it is now at OPC Tonbridge & had a phone call yesterday to say they were ordering an engine temp sensor & would change that.
Just had another call to say that it hasn't fixed it & it looks like a wiring fault between the engine bay & the relay. Investigations will continue.
The last time I had a problem like this was on a Renault 25 V6 23 years ago, didn't expect this sort of wiring issue on a Porsche

Sorry only just seen this!

From memory (I know it is the case on some boxsters) there is a water pressure sender and a temp sender that are both wired into the main engine management computer (DME/ECU).

When the right conditions are met, the ecu then outputs a signal to the fan relays (4 in total, one for each side on low speed, one for each side on high speed)

I recently had a 996 in with the similar wiring, dme etc.. which had the same problem. Turned out to be caused by a faulty dme, which cost about £250 to be repaired by my ECU guru.

More often than not, the fans pack up, or the resistor packs die.. you can jumper the relays to force them on in each speed one by one to rule out the fans, resistor packs or wiring. Then you can check out the relays by bench testing them with some lengths of wire, crimps, a bulb and a car battery.

I have not known the temp sensor or pressure switch to fail.

You may have a massive air lock though, this fools the pressure switch into thinking the coolant pressure is not high enough for the system to be heated up.

Jon & all an update on this. Currently OPC have found the following:- All the relays, fans & resistors are OK. They changed a sensor on the engine & reckon the DME is good. Apparently if you ground the relay connection then the fans are fine but something is high resistance between the DME & the relay wiring, therefore they don't get switched. I've just authorised another chunk of hours for investigation.
Jon, the DME fault you had, did it look like the above?

Jon, OPC Tonbridge have confirmed fault is the DME. This is on a 2000 W 3.2S Tip.

Several questions if I may please?

1. where is the DME & how easy is it to remove?
2. If I can get a DME from a s/h Boxster of the same year are they coded to the car, will it need recoding to mine?
3. How quick does your guy turnaround DME repair? I have BBA Reman just down the road but they say they need the part no. to know if they can test it.
4. Bearing in mind 2. got a s/h one?

did you get a warranty with this Jim? you have only had it 5 mins

1 on your Boxster it should be in the boot, behind the carpet on the bulkhead to the engine bay

2 they are coded to the car, but I believe it is more that the other units such as alarm are coded to it. I believe we have coded used dme,s in the past, but usually we repair them

3 about 4 or 5 business days usually

4 not got a used one. But they are not worth a lot because not just any garage can recode them, this also means some breakers only sell them as a set of DME alarm and key heads... Which is not advised, as you will never be able to have all the security codes in the future and would end up having to change the lot again

Thanks Jon, June busy for car events, July quieter so will investigate it later & find the part no. BBA Reman are literally 10 minutes from here, but if they can't do it then I'll parcel it up & send it down to you.

That is a conversation I'll start Monday. It was a tiny little garage & the Boxster was by far the most expensive thing that they sold. I've had it just over 2 months. Under the SOGA they have to cover 6 months & I believe 3 months has a different status as well, so we'll see what they say.

The car is now back & assuming I keep the climate on then there is no problem. They have checked it over & found a few other issues as well. Some important some not. Cracked coils, non-N rated front tyres, damp OS rad & condensor.

hmmm hope it was cheap