ZX cool air from vents

Paul Thomas · Post by **Paul Thomas** » 25 Feb 2004, 20:13

I have a 1993 ZX TD.
More recently I have noticed that I can't get hot air out of the heater vents only warmish air. After 5-10 mins the engine is up to half way on the temperature gauge but the air coming out of the vents isn't exactly what you would call hot !!
I replaced my coolant last year and bled all of the system correctly.
If I adjust the temperature control knob from hot to cold it works ok and then back to hot it gets warmer but still not hot enough.
Any suggestions ??

Post by **RichardW** » 25 Feb 2004, 20:30

Paul,
First check the coolant level - if it has dropped the first thing to go off is the heater. If it has dropped you need to find out why!
What does the temperature gauge do? It should come up to 80 and stay there - even in this cold weather. If it is only getting up to 65/70 in normal running, then the stat has failed open.
I guess there's a possbility the hot air control has become detached somewhere and is not giving you full hot.
Of course, it's 'kin cold outside so you will need more heat 'dialled in' to get the same temperature in the car.......
Make checking the level the first priority though, as the TD engine has a serious dislike of running with not enough water!

Nikolaymk · Post by **Nikolaymk** » 26 Feb 2004, 02:57

Or maybe the heater matrix has gone?

Paul Thomas · Post by **Paul Thomas** » 27 Feb 2004, 16:08

[:)][:)]UPDATE:
I checked the coolant level as suggested, it was low and required approximately 1L.
When driving along, after about 5 mins the temperature gauge goes up to 90 (1/2 way) and then drops back down as I presume the thermostat opens. It then slowly climbs back up to 90 and stays there as the whole engine and radiator warm up.
Topping this up still hasn't sorted out the cool air though.
I will have a go at bleeding the system again on the weekend and see if this helps.
How would I tell if the heater matrix has gone ? it certainly isn't leaking into the cab.
Is it worth changing the radiator cap, could it be leaking fluid out when hot ?
Perhaps worth flushing the system through ? I used a holts 2-part flush on my L/R Discovery last weekend along with a thermostat change which has totaly revitalised the system and it runs nice and cool now.
Has anyone tried one of those presurised refilling/test kits ? I presume they attach to a spare tyre like the clutch/brake blead kits and then push the replacement fluid around the system ? Perhaps this would be a good investment and ensure that no air pockets form ?

Post by **RichardW** » 27 Feb 2004, 16:18

Paul,
The low level will defo cause the heater to stop working - only question where did it go??? Doesn't sound like the matrix has gone (Phew!) as this would be wet carpets and steam out the vents time. Could be radiator or a hose, or water pumps or (shhhhh!) head gasket. You will need to bleed it to get the heater to work again. Front on ramps, header tank on the radiator and open those bleed points. I see on my 95 TD there is a bleed hose coming off the heater inlet which terminates by the RH suspension strut, which should make things pretty easy to bleed. Oh, and try and avoid running it too much before you bleed as you may well see off the HG.....

Paul Thomas · Post by **Paul Thomas** » 27 Feb 2004, 16:34

Is the head-gasket a big job on these ?
Any idea of cost ?
I've done 116,000 miles, of which I've owned and serviced it for the last 66,000. It's never had a head gasket in this time.

Post by **RichardW** » 27 Feb 2004, 16:37

Don't go there until you have no other options! Fairly big job - prob in the £300 - £500 region depending on what's found, and your local mechanic's hourly rate!

zxdyson · Post by **zxdyson** » 27 Feb 2004, 16:53

Hi,
I had the same problem, which ended up being head gasket. Did the job myself, with the head off i had it leak tested and skimmed (£65) then put it back together with new bolts and gaskets (£70). So all in all it cost £135 and is still running well. If you do it your self be prepared and read all relevant bits of the haynes manual before hand to save frustration and time.
Cheers, Mark

Paul Thomas · Post by **Paul Thomas** » 27 Feb 2004, 16:54

How long did it take ?
Big job ?

Post by **RichardW** » 27 Feb 2004, 17:06

Paul,
Don't give yourself a coronary over something that might not be! First, get the system bled, and see where that leads you. Have a good look over for leaks - the radiator and water pump are favourites. HG symptoms include air bubbles getting in to the coolant (run the engine with the cap off to see this), the system pressurising very quickly after start up (remove and replace rad cap, start (cold) engine and run for about 30s, stop engine, remove cap and listen for pressure release - any will be due to gas getting into the coolant rather than heat induced), residual system pressure in the morning.
The head gasket on these engines is not that difficult, but it's not for the very inexperienced. It'll probably take somewhere between 4 and 6 hours to get the head off and the same to reassemble it. If you would be happy changing the cambelt, then you can probably do the head gasket.

TomH · Post by **TomH** » 27 Feb 2004, 17:53

I had the same problem, but it ended up only being an air-lock.

Paul Thomas · Post by **Paul Thomas** » 27 Feb 2004, 18:42

Decision made, I will flush with Holts two-pack this weekend followed by thorough flush through with hosepipe.
I will take opportunity to fit new thermostat while it is all clean even though it hasn't gone. (Original after 116K miles)
Refill and thoroughly bleed.
I'll let u know next week !!

Paul Thomas · Post by **Paul Thomas** » 01 Mar 2004, 14:11

UPDATE:
Flushed, flushed & flushed again with Holts 2-pack.
Existing coolant in good condition but changed anyway.
Engine is now running at 80 mark rather than 90 mark previously. Changed thermostat as well.
Thoroughly bled system as recommended on posts in this forum, absolutely no air left in it now !
The pipes in and out of the bulkhead for the heater matrix are both hot and seem to be flowing ok.
Still hasn't resolved hot air problem though !!
Where do I start from within the cab, could it be the control cable ?
I have fitted a new stereo a couple of months ago, perhaps I have disturbed one of the control cables ?

Simon Canfer · Post by **Simon Canfer** » 01 Mar 2004, 18:04

Just something to check: have you had a peer into the radiator/header tank with the engine running, to look for bubbles? It's an early sign of head gasket failure.
I did the 'head on my ZX TD a few years ago, took my time over a week and quite enjoyed it!! Certainly preferable to a Sunday panic job.
Sounds like you have a heater control problem as you've hot pipes though; do yourself a favour and change all the dash bulbs you find otherwise they'll blow as soon as it goes back together

Simon Canfer

Post by **Jon** » 01 Mar 2004, 20:48

Try and lay backwards with your head in the passenger foot well and look up behind the dash towards the centre. You will be able to see the two cables for heat hold to cold, and the other that operates the flap from windscreen to floor / vents direction.
Get an assistant to operate the cold/hot heater control, slowly. If its working OK you'll be able to see the cable moving the flap. Sometimes these cables bend or come off, its definately worth checking if the rest of the cooling system checks out.