M

matt101

Member
Hi All,
I own a 300tdi discovery, I have had it over 4 years now and the heater has never seemed to work great.
It blows only warm air out, not hot.
There are no leaks anywhere, I have bled the system so I am positive there is no air trapped in the system.
Could this be a problem with the matrix?
I have taken the heater hoses off and put water through to check there are just blockages, all ok.
The engine always gets to temperature and the gauge stays in the middle.
Any ideas greatly appreciated.
Thanks
 
Heater warm but not
hot is believe a Tdi thing as the engine is cool running also very slow to heat up compared to the petrol engine D1, u say it gets up to temperature so what is the temperature? if water is flowing through the heater matrix ok then there's nothing wrong there, you may have an incorrect or faulty thermostat fitted.
 
Last edited:
discool said:
Heater warm but hot is believe a Tdi thing as the engine is cool running also very slow to heat up compared to the petrol engine D1, u say it gets up to temperature so what is the temperature? if water is flowing through the heater matrix ok then there's nothing wrong there, you may have an incorrect or faulty thermostat fitted.
Click to expand...

IME, It was an issue with the earlier ones my 95 was a bit as you describe, but both the 97's we have now are bl@@dy brilliant - but both have new genuine thermostats in - So.... check this -->

Marmaduke said:
Do the pipes that go to the heater at the back of engine get hot?
Click to expand...

and if not, then I'd change the thermostat - and if that doesn't work, then I'd be thinking about the water pump not pumping hard enough....
 
Yes this may be a thermostat issue.
After I rebuilt my 200tdi the heater was brilliant, I replaced the thermostat of course.
 
Thanks for the replies.
When I say it gets up to temperature I mean the gauge gets to the middle and that's where it stays.
Both hoses that go to the heater get hot.
The water pump has been replaced, this made no difference.
I don't think the thermostat has been changed however so maybe il give this a try next.
Thanks all
 
If the temperature gets to the middle and the pipes are hot I can't see it being the thermostat, if it were the gauge would be lower. I'd say it's some sort of blockage in the air side of the heater system.
 
matt101 said:
Both hoses that go to the heater get hot.
Click to expand...

Any chance you can measure the temperature ? ( I'm thinking non contact IR thermometer ) - if they are getting HOT, then I agree with Marmaduke - probably blocked on the air side....
 
Could also be a clogged up heater matrix, although it isn't totally blocked it could be quite clogged up .i.e doesn't hold much water or have a high flow rate.
 
The heater matrix inlet pipe should be nice and hot, and the outlet back to the engine bay noticeably cooler, if both pipes feel exactly the same or very similar temps (and the engine is up to temp with a good thermostat) it's probably clogged up with 20+ years of fluff and not radiating its heat very well in the cabin. (much as marmaduke said).

You mentioned flushing the matrix before, but back-flushing the system with a garden hose at modest pressure (less than 10psi for certain) can clear out silt deposits better than a standard system flush, as another idea

Not related to eventual max heat output but putting a new oil cooler thermostat in my 300tdi improved warm up times from 3-5 miles or so in the morning down to 2-3 miles (depending on outside temp), as the old one had stuck open.
 
Thanks for the additional replies.
I have ordered a genuine thermostat today (figured is maybe the cheapest option and worth replacing for peace of mind anyway).
As for the heater hoses, from memory both were just as hot as each other.
I will get the engine up to temp tomorrow and recheck this.
I will also try the hose pipe and put a little pressure into the heater system and see what comes out.
Thanks again.
 
matt101 said:
I will also try the hose pipe and put a little pressure into the heater system and see what comes out.
Click to expand...

I think the lower hose is the outlet (the side to flush from). Can't remember off the top of my head though
 
Definitely go for the thermostat. I had the same with my Disco 1 and replacing the stat made a world of difference.
Quite an easy job. Make sure you get rid of any air in the system. One way is to leave the engine running for a wee while with the expansion tank cap removed. This was told to me by a retired LR workshop foreman.
Remember to let us know how you get on.
 
Hi all,

Quick update. I replaced the thermostat with a genuine part this morning, I also ran the hose pipe through heater matrix as stated above (was just clear coolant coming out, no sludge etc)
Ran the car up after and I have now have heat!!
It's 100% better.
Thanks all for your help with this.
 
Funnily enough mine has started doing the same, had anyone used a bearmach thermostat? Only as as I have one amoungst my spares, I’m going to need a new housing too as the metal fill plug someone has fitted is seized solid.
 
I'm finding that some things are better fitted once and have been buying a lot of genuine parts to fight reliability issues, coolant & engine oil thermostats are winging their way to me courtesy of LR main dealer, £15 for coolant thermostat, £33 for oil stat
 
Just as some feedback for anyone that finds this in the future.

Fitted a new old stock thermostat housing as the fill plug was seized in place. This had what appeared to be a genuine thermostat in it so used that. No real difference, car got to temperature quicker so maybe the old one was stuck but still barely any heating.

Swapped out all of the coolant hoses and expansion tank yesterday, while doing that we also flushed the heater matrix. Very little flow to start with until loads of brown gunk came flooding out. Gave it a thorough flush in both directions with a hose and now the heater is really hot, lovely!
 
Coolant has a life span and it should be changed and flushed through but as with all things, second and third owners are never very good at keeping up with the maintenance.
 
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