Intro & Advice Re Cooling System

[dt917]

First of all, I'm new here, and didn't imagine that my first post would be about a problem. I've been an enthusiast since the days of Siffert, Elford and Rodriguez, but only recently managed to acquire an entry-level 10-year old 2.7 Boxster. It hasn't proved as involving to drive as the Lotus it replaced (although that may well be because I haven't explored it's limits yet - which would require a track day) but I love the looks, the comfort and the performance.

Unfortunately I have hit two problems - one practical and one geographical. Yesterday morning was frosty, so I ran the engine for 5 minutes before driving into town. It was beginning to warm up as I drove off, but after 3 kilometres I realised that the temp warning light was flashing and the guage was reading zero. On previous cars a zero reading would indicate the absence of any coolant at all for the sensor to read, but the level in the expansion tank looked fine. (It has since gone down, but not by a lot and there is no obvious leakage from the car.)
I suspect a failed cap, split tank or failed water pump, but am curious as to why the guage is reading zero. Can anyone suggest an explanation or tell me where the sensor is located? Also, there was less pressure than I expected when I loosened the filler cap, which is suggestive. Does the warning light work by means of a pressure sensor? It now flashes when switching on from cold.
In previous cars, with coolant in the system and a functioning temp. guage I would risk the 2 km run into town, but in this case there would be no warning before the engine was wrecked, so that's out.

The secondary problem is that I am in the Dordogne at present, which appears not to boast even a single Porsche dealer - so I'm struggling to find anyone who can be trusted to recover and fix it.

Any information/advice much appreciated.

[tr7v8]

OK, the coolant light flashes because of low level in the header tank, not heard of reliability issues with them but always a first time. Header tanks split fairly common issue so worth a look.
Unlike older cars the temp gauge is not directly connected to the engine sensor, it uses the DME (engine management) & the sensor feeds that then the DME outputs a signal to the gauge. It is very slugged, in other words it indicates middle of the gauge over quite a temp range. If you buy a cheap OBD2 reader like the ELM327 ones & TorquePro for an Android phone you can get the true temp from the engine. Be careful it is an all ali engine & cooking it will be fatal to the engine & wallet!

[dt917]

Many thanks for the response. Now really puzzled as to why the temperature guage should have stopped reading at the same time as the light started flashing - but I guess it's so risky I'll just have to find a tow or recovery truck, if possible. I'll report back if the solution turns out to be instructive.
David

[Chris H1]

Four functions of the coolant warning light:

1. Engine coolant level too low
— light flashes slowly (0.5 Hz)
2. Engine compartment temperature too high
— light flashes slowly (0.5 Hz) (engine compartment blower might be faulty)
3. Engine coolant temperature too high
— light is lit; pointer on the right
4. Temperature sensor at water outlet faulty
— light flashes rapidly (1 Hz); pointer on the right

Note
The temperature warning in point three is indicated if the conditions "engine coolant temperature too high" and "engine coolant level too low" are present simultaneously
(1Hz = 1 flash per second. 0.5Hz = 2 seconds per flash)

The temp sensor is located at cylinder 4 on the engine & I have seen reports of the wire breaking which would give flashing light + gauge not reading as described. The level in the header tank is read by a sensor at the base of said tank & again can fail/stick.

As Jim said get yourself something that will read the codes

Fingers crossed its one of these simple (all be it a pain to get too/find) problems.

HTH

[dt917]

Thanks, Chris. From your info it sounds as though the only problem I have is with the sensor, if I have understood correctly. I have a zero (or no) temperature reading and a 1Hz flashing warning light. Which presumably means it's safe to drive as far as the nearest garage after checking the coolant level once more. Or have I got that wrong?
Thanks, David

[dt917]

Apologies - just re-read with brain in gear and answered my own question.