TD with no heat

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rossnunn
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TD with no heat

Post by rossnunn »

Hi one & all.

ZX 1.9TD that produces not heat whatsoever from any of the vents.

We've disconnected the pipes into the heater matrix & flushed them through ok, we've removed & tested the thermostat, works fine, we've drained, flused & refilled the rad & still no heat at all from the internal vents.
The rad is pretty much had it & is loosing water but would this stop all the heat?
The input pipe to the heater matrix is getting hot but the return isn't all that, but we've flushed water both ways through with no problems.
All other pipes are getting hot as per normal & the footwell carpets are not wet.

I rekon a new rad should fix it, or there could be a flap in the matrix not open but would be interested in you guys input.
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NiSk
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Post by NiSk »

Sounds like someone filled it with some patent leak stopper and forgot the rule about opening the heater control fully . . .

//NiSk
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Post by Peter.N. »

If the matrix is clear and the water is circulating, the return pipe should be nearly as hot as the flow, are you sure you havn't got the pipes the wrong way round as this will cause the heater to fill with air. Replacing the radiator will only serve to cool the water even more. If the car is running normally and not overheating the water must be circulating OK, I can only suggest otherwise that the flap is stuck in the cold position.
Dave Burns
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Post by Dave Burns »

There should be hot water going throught the matrix at all times when at normal operating temp, regardles of any settings of the controls in the cabin.

Only one pipe to the matrix getting hot means hardly any water flow through it, if you have got water going through it ok when it was flushed then its probably air locked, you don't mention any bleeding of it.

Even if the pipes are connected backwards it will still work ok, just that the water would be going in the other direction through the matrix, since the pipes are moulded to shape it would be difficult to get them wrong anyway, but just in case they are not connected at the proper point, one pipe (feed) comes from the back of the cylinder head, the other (return) goes down to the water housing at the back of the block.

Is the thermostat the correct one, it should have a disk of about 1" dia. at the back that shuts the bypass flow off when it opens, the bypass is open when the thermostat is closed (cold engine) this recirculates water through the block/head for rapid warm up, if it remains open it will reduce the pull of water through the matrix.

Dave
rossnunn
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Post by rossnunn »

Thermostate looks to be the right one.

when I've said flush we've taken the two pipes off not right up at the matrix but at the next joint (right of the block), put a hose up one & flush the water out the other then did this round the other way, both times we had good water flow.

The car does not overheat, although he has had it once last week when overtaking come cars the temp gauge went right into the red, it had no water again.

there is a small pipe that goes from the bottom left of the rad into the water lines, this gets hot as does the main big pipe that feeds the thermostat.

We've bled the system to remove any air although I'm told that it will make its own air lock after a few days of driving, how true this is I don't know.
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James.UK
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Post by James.UK »

Hi Ross. Not much of this is making sense, (A) water circulates through the heater all the time, the controls simply direct where the heat created goes, so pipes in and out should be almost the same temp..

There is a bleeder above and to the left of the heater pipes where they go into the bulkhead, make sure you let air out using this when bleeding the system..

Behind the dashboard heater controls there is a cable that moves the flaps in acordance with the position you select by turning the dial. On my ZX there is a no-go area between 12 oclock position and 3 oclock position, you have to go round the other way. !2-9-6 3 and back ok..

If the dial is forced to go from 12 to 3 by turning clockwise, this will make the clip holding the cable come off. so the controls will no longer work.. Replacing the clip will solve that problem..

Thats all I know about the heater and its controls, I hope it helps..

I believe (not 100% certain) that the water leaves the rad through the large pipe at the bottom left hand side, and returns via the thermostat and large pipe top right. The water is driven by a pump.. Sooo, unless you have a major blockage, not enought water, faulty thermostat, an airlock, or the pump has packed up.. I cant see why the heater matrix would fail to get hot.. :?
James. (Nr M67 East of Manchester).
Dark Blue ZX 1.9D Auto 1994 'L' 5 dr (modified) Aura. 98K miles used daily. Ave mpg 40
Wedgewood Blue 75 CTD auto Connoissaur. 2002. 144k. used daily. ave mpg 40 ish.
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Post by jeremy »

I had a defective thermostat on our 1.9D Zx and the the heater still worked - just rather slowly. I'd expect some warm air out of it, even if what happened was that the matrix got hot when you turned the fan off and quickly cooled when you turned it on.

From the sound of it - no heat at all - a flap must have become stuck/disconnected. There must be an effective flap somewhere to shut off the heater in summer! - not that I've noticed much cool air flowing into the thing!
jeremy
JohnT
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Post by JohnT »

The system is simple.....when hot water is resticted in entering the matrix it will produce cooler air. If the hose to the heater is hot and the outlet is not it must be the valve; a blocked matrix, or the water returning to the heat source via the hose is blocked. I do not see how the thermostat is at cause here? As far as I am aware the 'flaps' direct air hot or cold to areas of the system, they have no effect on the heat produced?
Cheers!
John
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fastandfurryous
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Post by fastandfurryous »

This sounds very much like you have a 90% blocked matrix. I have the same problem on my 405 at the moment, and I'm afraid it's a new matrix required.

The way almost all matrixes work is the hot inlet is then split to go through many (maybe up to 20) pipes through the actual matrix, and then these 20 pipes are brought back to on for the outlet. Its very much like a radiator. One inlet, multiple cooling pipes, and one outlet.

What happens is that most of the pipes block, and leave just one or two clear. You can still get modearate flow through the matrix with a garden hose at mains pressure, but in the coolant circuit, there is very little flow. Only 10% of the matrix gets hot, the rest is stone cold giving very little heat output, and the return pipe to the engine is cold.

New matrix, problem solved.
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James.UK
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Post by James.UK »

Hi JohnT.. quote

>>If the hose to the heater is hot and the outlet is not it must be the valve<<

There is no valve on the matrix circulation route in my ZX, water just goes in one side, through the matrix, and out the other.. The only valve involved in the whole system is the thermostat as far as I know.. :)
James. (Nr M67 East of Manchester).
Dark Blue ZX 1.9D Auto 1994 'L' 5 dr (modified) Aura. 98K miles used daily. Ave mpg 40
Wedgewood Blue 75 CTD auto Connoissaur. 2002. 144k. used daily. ave mpg 40 ish.
JohnT
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Post by JohnT »

Hi James
If there is no heat valve (possibly part of the matrix) then how is the heat output regulated? The thermostat will not regulate the heating unless it is faulty and passing cool water, so no heat. There must be a flow valve to restrict the flow of near boiling water from the engine running at normal temperature?
Cheers!
John
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fastandfurryous
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Post by fastandfurryous »

JohnT wrote:If there is no heat valve (possibly part of the matrix) then how is the heat output regulated?
By having a cold air bypass, and a flap that selects a percentage of very hot air, and a percentage of cold air. This is an Air-blending heater, rather than what you are referring to, which is a water valve heater.
There must be a flow valve to restrict the flow of near boiling water from the engine running at normal temperature?
Nope. Full flow of 80-90 degree coolant all the time. Except in this case, where the matrix is blocked.
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jeremy
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Post by jeremy »

The ZX heater is of the 'Air Blending' type which have no water valve and rely on flap valves to control the volume of hot air entering the cabin. The matrix is always heated, its just a question of how much if any air flows over it into the cabin.

Theoretical advantages are a quicker response to controls (you haven't got to wait while the matrix warms up (except of course when the car is cold)) and you have no stiff and expensive water valve to leak.
jeremy
JohnT
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Post by JohnT »

Thanks for that, you learn something every day!
Cheers!
John
micitroen
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no heat

Post by micitroen »

However there was one advantage to the old system of a reservoir of 'cold' water sitting in the heater.......when the car started to overheat (usually in the summer) you could turn on the heater and fan and release another litre or so of cold water into the system. Usually involved opening the windows and sweating a little but I can remember using this to get me out of trouble quite a few times on my old Triumph Vitesse 1600/6. Still remember the no. plate; 811 CVB... wonder if she's still alive?
Mike



1993 BX TXD EST mmm. nice. 1990 Bx 19TZD Auto Lhd (now lives in France) 1998 Xsara 1.9d lx.
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