Xantia TD 1995. Running lukewarm. Changed thermostat.

JohnT · Unread post by **JohnT** » 22 Jan 2007, 18:11

I have tried two (one new) stats and checked them with boil tests on the stove. Even after a ten mile run the engine is not very hot. It will take at least seven miles in the morning to get the heater medium warm (ish). By this time the rad is not hot overall.
I have vented the system.
At no time does the unit get hot enough to turn on the fans. I have left it on fast idle (1200) for 30 minutes, the engine gets very warm, not hot, and the system equalises but it aint really hot!
There is no point blanking off part of the rad with cardboard or the suchlike as the rad is not hot enough in the first place?
Any ideas please? I am not a dunce with these cars but am staring at the obvious?
Thanks to all who reply.

jeremy · Unread post by **jeremy** » 22 Jan 2007, 18:20

Sounds like poor flow through the heater - either air in it or its blocked.

An alternative is that a heater flap has dropped off or is not working properly. Its an air blender which means that there is no water valve.

The gauge on our ZX 1.9D will drop if it idles in cold weather - as in a traffic queue but the heater still works nicely. The same is true for my BX Turbo.

KP · Unread post by KP » 22 Jan 2007, 18:27

As above give the system a good flushing with a garden hose untill it runs clear from both directions of flow. if you could single out the heater matrix i would flush that gently and see if that improves the heat at all.

Unread post by **Peter.N.** » 22 Jan 2007, 18:58

Does the radiator start to get warm at all soon after you have started the engine? if so, it could be that the water is somehow bypassing the thermostat. If the cooling system is in good condition, and the thermostat is not being able to restrict the water flow, in cold weather the radiator wont get hot because it is disposing of all the heat as the engine is producing it. Feel the top hose or top of the radiator as soon as you start the engine, it should stay cold until the engine reaches normal temperature and the thermostat opens. If not check that the seal is present on the thermostat and that it is actually sealing.

JohnT · Unread post by **JohnT** » 22 Jan 2007, 23:18

Thanks for the replies, perhaps I put in to much detail in the post as the answers to your points you are making are there. Peter asks as to whether the radiator gets warm soon after running. No it does not. (Hence no hot coolant going to the heater matrix) He then suggests that the water flow is a problem and is being by passed elswhere? I think he is on to the problem but I know not the answer. The heater matrix is not at fault, the two pipes are of nearly equal temp, not hot, but only warm after a long run. Yes I appreciate it is an air mixing system but that is not the problem.
This is not an easy one..........the detail I listed is being overlooked but thank you for your contribution anyway. Any further help will be appreciated. Cheers, John.

JohnT · Unread post by **JohnT** » 22 Jan 2007, 23:23

I think I have not anwered the point Peter made correctly.........the heater does have warm water supplied whilst the rad is still cold, but not hot. The supply/return pipes are never at any time hot.

UFO · Unread post by **UFO** » 23 Jan 2007, 04:43

The feed and return pipes to the heater should be hot as they are fed and return direct to the "closed" engine system prior to the thermostat opening. Only after a decent run time should the radiator and its pipes come up to temp as the thermostat opens.

I suggest that your heater core is blocked. It sounds simlar to this XM problem

http://club-xm.com/forum2/index.php?showtopic=1603

Unread post by **Peter.N.** » 23 Jan 2007, 09:19

If both heater pipes are at more or less the same temperature that would seem to indicate that the water is flowing through the heater matrix OK. Does the engine temperature feel about the same as the heater pipes? If so then the heat is being lost elswhere the only possible route is through the radiator. You could prove this by the time honered method of stuffing some cardboard down the front of the radiator, if you engine now gets warmer, which I suspect it will, you have a problem with coolant bypassing the thermostat. Incidentally, does your thermostsat have a venting hole in it?

Unread post by **RichardW** » 23 Jan 2007, 16:37

Obvious has not been stated - what does the gauge say?

My TD runs at 70 - which is cool, and I think an after effect of adding Forte sealant to stop the matrix leaking. However, it reaches this temp after about 3 miles, and there's plenty of heat from the heater.

howiedean · Unread post by **howiedean** » 23 Jan 2007, 20:10

RichardW wrote:Obvious has not been stated - what does the gauge say?

My TD runs at 70 - which is cool, and I think an after effect of adding Forte sealant to stop the matrix leaking. However, it reaches this temp after about 3 miles, and there's plenty of heat from the heater.

John,
What does your temp guage read after a good run? Mine always sits at the mark between 60 and 90. I've just replace the thermostat on mine as I thought that this was reading a little low. My previous HDI used to indicate just under 90.

BonceChops · Unread post by **BonceChops** » 23 Jan 2007, 20:32

Peter.N. wrote:If both heater pipes are at more or less the same temperature that would seem to indicate that the water is flowing through the heater matrix OK.

But he says they are not hot, just warm. This could be a blocked matrix and the pipes are warm by conduction in the water.

I would try removing both pipes from the matrix and try passing water through with a hosepipe. Carefully with it turned on only a bit to avoid damaging it.

Unread post by **Peter.N.** » 23 Jan 2007, 21:47

It could be that the engine is only just warm, that's why I asked him to check. If the thermostat is not operating properly in this weather the engine wont get hot at all.

Unread post by **alan s** » 23 Jan 2007, 22:17

Don't take it for granted that because the thermostat is new that it's operating OK.
I once saw a mechanic test a box of 20 thermostats for a Toyota before he found one working correctly.
I recently also saw a posting regarding thermostats that I didn't take a real lot of notice about at the time, and it was in relation to some thermostats requiring a small hole to be drilled in the flange to make them work properly.
It was something to do with a batch coming out minus this hole. I can't remember what effect the lack of this hole had on the thermostats operation, but it may be a line worth investigating in case you're a victim of "the (made in) China syndrome".

Alan S

[edit] BINGO - Found it!!

It's a long winded thread that gets as far off topic as is possible, but if you sift through it, I think you might find the answer in there.

http://208.109.104.50/forum/showthread. ... thermostat [/u]

Unread post by **Peter.N.** » 24 Jan 2007, 11:16

Most thermostats used to have this 'hole' , sometimes with a little 'ball valve' arrangement in it. The purpose I believe is to vent any trapped air and also allow a small ammount of water to flow past the capsule or bellows as it was in those days, to ensure that the thermostat was activated. Sometimes though, in very cold weather, the ammount of water passing through the hole was enough to prevent the water reaching proper working temperature.