C5 X7 2.0HDi engine temp.

[milleplod]

Had a trip up the M1 today to drop my daughter and friends off at Meadowhell. I glanced down at the instruments and was surprised to see the temp gauge showing only 1 bar, which then disappeared to 0 bars. As I exited at j34, a couple of miles later, the gauge came back up again to the halfway point, which is where it usually sits, and then stayed there for the rest of the journey. I had a new thermostat fitted at the back end of last year - I usually get hot air within a few mins of starting, very hot a few mins later, and the gauge shows 'normal', 4/5 bars, after only a few miles. This morning was no different.

I didn't have the presence of mind to check what sort of temp the heater was providing when the gauge dropped, I was glued to it and half expecting some sort of warning hooter going off to tell me all the coolant had just been dumped! Oh, coolant level looks OK too.

Was I getting super-cooling from the very strong (cold!) wind I was driving into?!

Pete

[GiveMeABreak]

Hi Pete, don't forget you'll have air resistance heating when starting the car for a while until the engine gets warm. Was the thermostat a kosher one - or one of the aftermarket variety? Quality does vary so am curious.

[milleplod]

Hi Marc.

Yep, I know about the resistance heating, I can feel that more or less straight away....just! The t'stat was a Febi one, so not genuine Citroen but decent (?) quality I think.

Pete

[white exec]

You should be able to assess whether the main stat is working, by feeling the temp of the hoses that run to the cabin heater and the radiator. After starting the engine and allowing it to run for 5 or so mins, the hose going to the cabin heater should feel warm/hot, and the one to the rad cold, as the stat should be shutting the latter off. If they both warm up at about the same rate, you know the stat is leaky or stuck open.
If stuck shut (very rare) there will be chronic overheating while driving.

[milleplod]

I reckon the t'stat's u/s! Just done a 15-mile round trip, after 5/6 miles, no bars on the gauge, then 1 bar showed just before parking up. Return home half hour later, only 2 bars showing just short of home, and the heater not as hot as it should be. Bugger - it was a pig of a job last time! It's under warranty, so just about to contact the seller....

Pete

[GiveMeABreak]

Did you drain and refill the coolant system last time is was replaced Pete (as per the replacement recommendation)? I'm just wondering if it needs bleeding / degassing which may be causing the odd readings.

[white exec]

And do try feeling those hoses, 5 minutes or so after a cold start.

[milleplod]

To add to the story.....just back from another 15-mile round trip. This time, it behaved perfectly - the engine would've been warm-ish from the earlier run out, but no bars on the gauge when I set off. Within a couple of minutes, I had 2 bars, and associated heat from the heater....few mins later, 5/6 bars and properly-hot heating....and it stayed like that for the whole trip.

Marc - no, no drain/refill when my mate fitted the replacement, but tbh it's behaved perfectly since it was done. It was actually fitted at the end of Jan this year, around 9k miles ago, so I'd have expected odd behaviour before now if there was anything amiss....I think!

Re the hoses - yes, I'll check them tomorrow morning after a cold start and report back. Could the 'stat be opening properly, and then partially closing again? Do they play up in that way?

Pete

[white exec]

'Stats can go leaky, stiff, sticky, all sorts, which can lead to erratic behaviour. No jokes, please.
Usually that get stuck open (or their rubber seals split), which makes everything run chilly - except if you use a bit of welly, in which case coolant/heater/engine will get up to normal temp, but then fall away again as you coast/go downhill/ease up on the power.

[milleplod]

Checked the hoses this morning after starting from cold - heater hose hot/rad one cold after 4 or 5 mins. Gauge and heater performed normally on the run out, so I'm thinking an intermittent fault.

Pete

[white exec]

If both hoses (heater and radiator) get warm at the same rate, then the 'stat is leaky/stuck open.
Heater hose should get hot well ahead of the radiator one, if the 'stat is doing its job.