citroen xantia v6 exclusive overheating

[JOHN XANTIA V6]

Hello
My name is john and i have an overheating problem with my xantia V6!!
One day i saw the temperature gauge rise very quickly. I stoped and i saw that one of the two heater matrix pipes was broken.
I forgot to mention that the bubble sphere was missing when i purchased the car .
I replaced everything with new parts ( including the sphere and the expansion tank).
Everything worked fine until i drove a long distance, and then the car started overheating (100-110 oC ) in high speed (more than 170 kmh). The temperature was returning to normal after slowing down.
After this incident, i always had to add a small quantity of coolant for normal -city- distance and speed, and today i noticed that the expansion tank was actually leaking around the seem.

Do you have any idea about a: the cause of overheating and also b:if this high temperature could be the reason why the tank broke?

Thank you

John

[CitroJim]

Hi John, welcome to the forum

Firstly a cracked expansion tank and a leaky bubble-breaker (degassing tank) are both very common problems on the V6 Xantia.

In view of the fact you lost coolant when a heater matrix pipe broke then the only conclusion is that one or the other head gaskets has failed.

Sadly, despite the ES9 engine being tough and durable one thing it cannot stand is any coolant loss. I have known several now go in exactly the same way as yours and always after an episode of coolant loss.

The ES9 does in my experience drink a little water normally but not nearly so much as yours does now.

On the plus side, the heads are easier to remove than it looks and a quick skim and new gaskets will see all right again. There is no need to remove the engine (remarkably).

May I caution that you never try to use a cooling system sealer of any type as they are known to block the transmission cooler which will (not may) result in premature gearbox failure..

The problem will get worse over time. When they really let go the result is spectacular. We have seen a geyser from the expansion tank.

Sorry to be the bearer of potentially bad news...

[CitroJim]

John, just another quick point.. I'm assuming the radiator is in good condition?

I ask as the V6 cooling system is a tad marginal at the best of times and a sad rad will not be helping... Normally they start to leak around the edges.

Also, what does your temperature gauge read in gentle, normal running? It should be quite low (around 60 to 70 degrees) as by a quirk of design the temperature gauge sender is effectively in the bottom hose and therefore reading water cooled by the rad going to the engine rather than hot water passing out of the engine.

A high standing temperature can indicate a bad thermostat - they're fun to change!

[Northern_Mike]

Are you sure about the head gasket Jim? I only ask because in my experience, when a head gasket goes and the car gets hot under extreme use - as 110mph can be classed as, they don't usually cool back down when you slow down.

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[CitroJim]

Yes, I'm speaking from experience here Mike and seen similar a few times on the ES9 and other engines. Inn fact it goes right back to a Poxhall Chavalier we once had in the 90s that suffered a similar fate and displayed the same symptoms...

Also, I'm reading that this behaviour only started AFTER the broken Heater Matrix hose.

[JOHN XANTIA V6]

Dear friends, thank you for your interrest!!
I must add that the normal cruising temperature is 80-90 oC and also that the engine reaches this figure very quickly, especially during the greek hot summer.
Now in the winter it reaches 80 oC (consider a mild winter)
The rad is in excellent condition, externally at least.

I also have to say that your points do not explain to me why a new expansion tank broke around the seem. Could this be the result of a over pressurized system and if yes, what is causing this high pressure? I assume that the cause could not be the high pressure because the tank has a pressure control valve in the cap. So?

[CitroJim]

I also have to say that your points do not explain to me why a new expansion tank broke around the seem. Could this be the result of a over pressurized system and if yes, what is causing this high pressure? I assume that the cause could not be the high pressure because the tank has a pressure control valve in the cap. So?

The tank is weak John. They fail very regularly even in normal use around the seam. If a new one went too that would indicate the cooling system is pressurising excessively which in turn suggest head gasket failure.

Did you replace the expansion tank cap? I'm assuming you did...

[JOHN XANTIA V6]

Yes i did.

[JOHN XANTIA V6]

If it was the gasket, by opening the cup in normal temperature , the engine should pressurize the coolant outside the tank, which is not what happens
when i tried it. Am i wrong??

[Northern_Mike]

Yes, I'm speaking from experience here Mike and seen similar a few times on the ES9

I'm not questioning you Jim. I'm merely saying on all the head gasket failures I've had - a Honda (Rover 416) a 2.1XM and a Skoda, all have simply started up and just got hotter and hotter until they boiled up. My Capri used to get hot im traffic but cool on the open road because the rad was blocked up. My MX-5 with the leaky rad used to get hot at speed and cool down when you slowed down.


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[CitroJim]

Point taken Mike which is why I asked the supplemental question about the radiator. OP says it's fine.

It may be worth swapping the thermostat but the fact the tank split worries me. Sounds like a lot of pressure there.