Heating Problem

[Bigjeeze]

My MK1 has a problem I can't work out.

 

I replaced the thermostat because although it gets warm it never seems to move the temp gauge off the minimum spot. I recently replaced the Aux Heater and that is working fine - there appears to be heat at both ends of the pipework - ie the heater works in the rear and the car interior will get warm - albeit slowly. When I changed the Thermostat I decided to check the rad top hose - This appears to get warm - but the bottom hose doesn't - at all. It would appear that the thermostat isn't getting hot enough to open or the rad may be blocked - but it this was the case why doesn't it overheat?

 

Has anyone any idea as this is driving me nuts!!

[Bigjeeze]

My MK1 has a problem I can't work out.

 

I replaced the thermostat because although it gets warm it never seems to move the temp gauge off the minimum spot. I recently replaced the Aux Heater and that is working fine - there appears to be heat at both ends of the pipework - ie the heater works in the rear and the car interior will get warm - albeit slowly. When I changed the Thermostat I decided to check the rad top hose - This appears to get warm - but the bottom hose doesn't - at all. It would appear that the thermostat isn't getting hot enough to open or the rad may be blocked - but it this was the case why doesn't it overheat?

 

Has anyone any idea as this is driving me nuts!!

 

Anybody?

[big_kev]

Sounds like a classic sticking thermostat.

 

Don't know if the water still flows to the heater matrices even with a stuck thermostat.

This may be enough to prevent over heating.

[billywizzo]

As far as i know, all thermostats should fail open as they are what stops the water leaving the engine block untill it is at running temp, then open to keep the engine at that temp.

When mine failed the temp guage only just moved but after a long time and it never really got hot through the heater only warm.

Is the engine temp reading normally now or still cold.

It may be worth taking both hoses off the rad and use a hose pipe to pass water through it and see if it is blocked.

Have you felt the rad to see if it is hot all the way down.

If the car runs at normal temp and hot is felt through the heater then i would not personally worry.

[Bigjeeze]

1)I replaced the Thermostat and have the same problem.

 

The car heats up inside fine but it takes a long time.

 

2) The Temp gauge never goes beyond just off the min mark.

 

3) The heater matricesi ( both front & back ) get hot and pump out hot air.

 

4) The rad seems to stay cold - the top hose gets hot but not the bottom one. Not even warmish.

 

5) The Booster heater is working and helps heat up the car but still very little movement on the temp gauge and it takes a long time - more than 30 mins.

 

It is possible the Rad is blocked yet surely it would overheat?

Edited January 12, 2010 by Bigjeeze

[gregers]

have you tried flushing out the rad?

[Scorpiorefugee]

Adding it all up makes no sense 'cos your engine is running and the aux heater is running and yet nothing is getting hot. Either there is no heat being generated (not possible given what you've described) or there is a lot of heat being lost (thermostat stuck open but that would mean at least tepid water out of the bottom and, anyway, you've changed the 'stat)

 

As I said - makes no sense.

 

Some thoughts - It has been bl00dy cold and when my aux heater failed to fire up a couple of days ago (It seems to have fixed itself now) I had similar symptoms. Are you sure its running?

 

Is it any better now it's a bit warmer?

 

If you agree my comments above it may be worth rechecking everything after a 10 mile run.

 

I just cannot see how everything can remain cold after a reasonable run even in this weather.

 

one more thought, when my aux heater failed I noticed an increase in the MPG as it wasn't 'wasting' fuel.

[Mirez]

Its not unthinkable that you just arn't getting up to enough of a temperature to fully open the thermostat.

 

Always start with the easy things! Have you checked with VagCom the coolant temperature? It maybe as simple as the gauge sensor is defective - login to the aux heater controller and go to measuring blocks - you'll see a few in there and I think on page 2 you'll see two temperatures next to each other which are in and out temps - whats the "in" temp? That'll give you an indication of the current coolant temp but its passed down some long pipes at that point so it will be generally higher then that reading. You can do the same with the "engine" controller and see what thats says as that should be looking at a seperate temp sensor from the gauge one IIRC.

 

With the current exceptionally cold temperatures I wouldn't expect the stat to be opening very frequently anyway but logically if you have heat from the vent then its warming up hence my thoughts on the sensor. IF you had a blocked radiator it wouldn't be reading low!

[Mirez]

Ahh Scorpiorefugee got in before me but basically thats exactly what I'm thinking, it makes no sense hence why I get a second confirmed reading for the coolent temp!

[acecard]

When I bought my TDi 130 2005, it took ages to warm up. Got them to replace the thermo under warranty but didnt improve matters too much.

Frequently on a 20 min drive on a slight downhill slope, it hardly gets to 60 on the gauge. Work it a bit on the same journey uphill and gets to 90 no problem.

If anything, I have less trouble in the cold as I get that reassuring tick from the aux heater and things warm up nicely.

My experiences with a sticking (closed) themo is that things fry pretty quickly but don't they tend to fail safe (ie open).

Possibly two dicky thermos?

[acecard]

Plus, if it was my ch system, I'd be 90% certain of an air lock. Not sure if you can bleed the system on gals easily - modern cars defeat me.

[Scorpiorefugee]

Lots of perfectly good ideas coming in but the question remains...

 

If physically feeling the temperature of the pipes confirms that it is running excessively cool then this is totally against the normal effect of overheating for just about any fault bar permanently open thermostat or totally wrong fuel/air mixture so, if everything checks out OK, where is the heat going?

 

I had the common problem of water pump failure a couple of years ago at this time of year and made it home at 55mph for 200 miles with a cold radiator with the cooling apparently being managed by the interior heating and possibly the plumbing for the Aux. heater by simple convection or the effect of the pump which circulates water to the aux. heater so, as I suggested earlier, it might be worth re-examining these areas.

 

While I can't argue against any suggestions re possible sensor problems, if the engine is not getting hot to the touch then this seems unlikely - but it still doesn't make sense.

 

Just one more point, my MkII Aux heater is on virtually full time at the moment and I do know that without it the temp gauge was barely leaving the bottom until I hit 70 on the motorway.

Edited January 12, 2010 by Scorpiorefugee

[gregers]

mines just like scorpios aswell,if im stuck in traffic the temp needle actually gos down,

only when im moving does it move.

[seatkid]

Theres nowt wrong - your temperature gauge or sensor isnt working. (might be wiring)

 

In this weather, its normal to have a stone cold rad - just a hot top pipe - especially if your run is not at high speed/power and less than 30 minutes. The Tdi is just too efficient and all the heat generated is being sent to the two heaters (front and rear)

 

Thats why you need a working booster heater thingy to speed the process and heat things up a bit. I also have insulated the pipework running to the rear heater on mine with that DIY foam insulation for 22mm pipe. Helps a lot in artic weather!

 

 

Heated seats - they're the bees knees......

Edited January 13, 2010 by seatkid

[Bigjeeze]

Thanks Guys

 

 

I think I may be misleading you.

 

The heater blows hot air after a long warm up - The Booster heater is working - there is also hot air coming from the rear heater vents once the car is warm - what is not happeneing is that the temp Gauge appears to move very little and never goes into the normal or central position.

 

I have noiw changed the t stat - renewed the Coolant and it will now stay like that come whatever!!.

 

 

The reason I picked up on this is that my MK2 is hot after 15 mins or 5 miles .

[Phil]

I have the same problem with my mk1 seat alhambra, i have changed the water pump, the radiator and the thermostat yet if i boot it all the way to work about 50mins away it will just about generate enough heat for the gauge to register 1/4 of the way

 

If i drive as i normally would then im lucky it the gauge reaches half of that, 1 thing i have noticed is that the water system stays pressurised for a long time, if i leave it overnight then it will still be pressurised and the water level rises.

 

i have flushed the system with a hose pipe with all heating valves open, the aux heater works fine (just replaced the glow plug in this as well).

 

im going to take another look this weekend as you are all right in that it seems that the coolant isnt being restricted to the rad until it is at operating temp, which is the thermostat job, so im gonna check the operation of that, ill do the boiling water in a pan test, also will check that the coolant isnt somehow managing to get around the thermostat (e.g the rubber seal isnt fitted correctly).

 

Phil

[tim-spam]

This sounds like a problem with the sender or gauge. Bear in mind also, when comparing Mk1 with Mk 2, that the coolant circuits are different and that the booster heater is 5kW on the Mk 2 as against 3kW on a Mk 1.

[TDIPAZ]

Hi to all. I agree with the sender unit being at fault. there seems to be alot of sh*t sender units on the market place. so even if you replace with a new one, be it a colour grey, or black sender unit- two pin ... a lot of patern parts do not match the electrical current rating required to match the temp guage unit/ecu. thus giving you the temp inacuracies. and also no doubt High reving on start up when engine is cold, as i get at the moment with the replacement patern sender along with all the problems that you have described. My original faulty sender unit, gave me high reving on start up, when the engine was warm..

So all i'm waiting for is wam weather, so i will be more enthusiastic to get this problem sorted. As its a right pain of a job to get to the unit out. from the back corner of the engine. ie. fuel filter in the way has to removed to get acess. My advice after my experience is - buy a genuine part- water temp sender ..Thats my next move. best of luck folks