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Hi all.
On several occassions I have asked and commented on running temperatures of Diesel Estates.My old MK1 2.1Td used to run at just under 70 degrees at 70mph.It would never go over 90 degrees even in a traffic jam,and I even had it go from 90 degrees to 56 degrees in a few miles after I started moving again.It had been suggested that the thermostats were permanently stuck open.
So now I have a 2.5Td and my main worry when I bought it was the reputation for a poor cooling system.So to my amazement it runs even cooler than my 2.1Td!On the motorway at 70mph it is at about 65 degrees!It goes up to about 90 degrees in stationary trafic,but it hasn't gone over this yet so I don't know if the fans are working either yet.I have done 1500 miles in it already so it has been well used.
Economy is around 40mpg with mixed driving and 45ish on a run.
So.........I think judging from previous posts,most 2.5's run at around 95 degrees.
My question is,am I doing the engine any harm by the cooler temperatures?If not I will leave as it is,but I find it strange that both my cars are running at a similar temperature.
The car is not using any water.
What do you think?
Regards Rob
PS.I "serviced" it today-changed the oil with 10-40W Semi synthetic,changed the oil filter(with a GSF one which was approx 40% taller than the one fitted),air filter and fuel filter.How difficult is it to drain and clean the LHM system with hydraflush?
HI Rob,

I have 2 2.5td's and they both run at 95 despite the catalogue of investigations covered elsewhere. 65 seems much too low as if the thermostat is stuck open maybe with some debris. The effect on the engine will be more emissions and slightly poorer economy. Just be sure the gauge isn't lying before doing anything drastic.

To test the fans just pull the brown connector off the top of the coolant outlet tank on the cylinder head. Both fans will start in slow mode and after 2 seconds they will speed up to fast mode.

I've never completely replaced my LHM in any Citroen I've owned. The replacement ratio due to continuous leaks have done that for me !! I think its well covered in the Haynes book of lies.


noz cool.gif
Hi Rob

GSF are one of the few non citroen spares suppliers who supply the correct Oil filter for 2.5 TD's. Most try to fob you off with the small 2.1 TD oil filter. The 2.5 actually takes the same oil filter as the V6 XM. GSF supply Purflux filters and the part was a LS520C, a filter more than twice the size of that used for the 2.1 TD. Sometime last year when I went to get my last lot GSF supplied PURFLUX LS880's which are not quite as tall as the LS520C. I made them provide catalogue evidence of the product change before I was satisfied they were supplying the correct part for the car.


Hi Rob,

I'd agree with Noz that your running temperature is way too low. Very strange that both your cars exhibit this.

I think 85-90 degrees is what you should expect (perhaps closer to 95 degrees if you're giving it some welly).

There's a lot of information on the 2.5TD cooling system in the (ongoing) post "2.5td Cooling System, Can it work? - you tell me !". Some of that may help you fix the problem and prevent any future coolant issues on your car.

I've recently flushed and replaced the LHM on my car and as Noz says it's well documented in Haynes. You need to run with the flushing agent for about 1,000 miles - so in effect you have to do the job twice. The worst part I found was dealing with the hose clips on the LHM reservoir. Is there a special tool for these (clip over and split pin type) does anyone know?

Hi Roy,

Yes Pleiades sell a tool specifically for those clips.


noz cool.gif
Hi all
I had a look at the file as it was being compiled and remember thinking I am glad I don't have a 2.5!Now you all know I am not an expert,but to my way of thinking it can only be the thermostat.The water looks clean on this car,my 2.1 looked like red ditch water!The water must be circulating well to enable it to run at this temperature,I would have thought if there was debris in the system it would not do this.The temp does go up quite quickly as soon as I stop in traffic,but then goes right down again as soon as air gets through the rad again.I have another 2K trip coming up,so it will be interesting to see what happens on some of the very long and steep motorway hills in France.
It is quite bizarre that most of you are wishing yours would run cooler and I wish mine would run hotter.I should add that at least 80% of my miles are on the motorways etc and not in town driving.When I put the heater on today it blew out very hot air.
The temperature gauge may of course be inaccurate,but it does move up and down the ranges mentioned smoothly.I find it strange that the cars are fitted with gauges that start at 50 degrees with 90 being in the middle and the "correct" running temp at this or even higher.
Anyway I am going to leave it as it is until the autumn,when I will drain the system and do the antifreeze.
What does your car run at Peter,as I think you do a fair bit of motorway driving as well?
Regards Rob
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