1999 Citroen Xsara Turbo Diesel Overheating At Speed

[B1981ci]

The car overheats rather quickly bit only at high speed on the highway (160-180+ kmh). This is the only time it does it though. Drive below 160 and it's fine. I thought maybe it could be the thermostat but if that were the case I would expect problems at any speed.

 

Car otherwise runs smooth, no noises, no lack of power, fuel mileage is great, etc.

 

What could be the cause of this and how do I if it.

 

I think the engine is a 1.5L turbo diesel but I'm not sure (it's definitely a 4 cyl turbo diesel).

 

 

Thanks!

[B1981ci]

It is an "xsara break (n2)" by the way. I guess if this info is accurate then it must be a 1.9 or 2.0 not a 1.5... http://www.auto-data.net/en/?f=showSubModel&modeli_id=1693

[Johndouglas]

You're right!   Your engine won't be 1.5 because TUDs were never used in early  Xsaras.   More likely to be the XUD9 which is a 1.9 turbo diesel.   I'm not surprised that your engine tends to run hot when you drive it in excess of 160kph.   Over it's 15 year life time it will have collected quite a bit of residue in the radiator and cooling system.    Even when the car was new and it was driven in perfect conditions (and probably stripped almost bare, it's maximum speed on the spec sheet was 170kph.   As you say, at a more moderate speed there's nothing wrong the car.  

[paul.h]

This post may be a wind up, apart from Germany where are you allowed to go over 160 kph (100 mph) and who would want to drive their car flat out ?

[coastline taxis]

Flush the cooling system out and get the head gasket checked. The cheapest way though would be to lift your right foot up a inch

[B1981ci]

I never owed a car that would overheat just because you drive fast and I've probably owned 20 or 30 different cars.  Some new, some old and high mileage, economy cars, sports cars, etc.  None of gthem would overheat just because you drive on the highway at, let's say 80% of the red line.  I also never owned a french car or a turbo diesel so I just wanted ot know if it's "nomral" or if anybody knows what can be the cause.

 

I am curious though why if it's crap in the cooling system does it not cause trouble at slow speeds?

[Johndouglas]

Just out of interest, where are you able to drive your Xsara at 170kph?

[paul.h]

At lower speeds the engine will be burning less fuel so there is less heat to be removed by the radiator but if you used the car in a low gear so it ran at the same revs as at 170 kph and used the same amount of fuel, then it would probably also overheat.

 

The heat removal rate by the radiator will depend on the coolant flow rate and air flow rate and the temperature difference between the air and the radiator - on a hot day it will be able to remove less heat. The radiator will have been sized adequately when new but if it is blocked on the outside by insects or other debris and on the inside it has rust and other dirt blocking the waterways, then its capacity for heat removal will be reduced. As well as cleaning out the radiator (or replacing with a new one), you should also check the fan is working and not damaged and the coolant is in good condition.