2001 Passat Heating Problem

greenermetals

My brother has a diesel passat 2001 (1.9, 130 BHP if that matters) she has up til now been going like clockwork but he recently has had problems with the heating. He has enough heat to keep his windscreen clear but not enough to keep himself warm. He took it to a mechanic yesterday (he lives in the north) and he said it was a problem with the water pump which would need replacing, which means taking the engine apart. Long story short, 120 pounds labour plus price of pump. He has no coolant leaks. Is this mechanic right? is that what the problem is? a short google search mentioned something about a valve. How would he be sure the pump is the problem before taking the pump out? Any suggestions what else it could be? Thanks for your help in advance

SurferDude41

Would very much doubt its the water pump.
The heater matrix (small radiator inside the dash) could be blocked.
Or the coolant bypass valve could be stuck closed.(Could be temporarily opened by hand )
Its either located under the dash, or on the firewall.
If you follow the 2 small coolant hoses from the engine bay, you are sure to find it.

Is the car running at normal temerature? (The temp gauge at 12 o clock)

When the car is started, one of the (Large) coolant hoses. The ones that run from the radiator to the engine( under the bonnet)
Usually the top one gets warm first, then the lower hose should begin to get fairly hot as well.

If this doesn't happen, the Thermostat is stuck open.
Its a €20 part in an autofactors.

Any car with that sort of mileage, should have the timing belt, waterpump and and tension pulleys replaced anyway.

Let me know how you get on.

Happy Motoring:)

deaglan169

seems to be common problem with vags this winter, im having similar problems car heats to 90c then cools down to about 75c and remains there seems to be when im stoped at traffic lights etc.. it drops, some times it only rises to about 75c and sits there, i had timing belt and water pump done so i got mechanic to replace thermostat when he was at it and i also changed the coolant/temp sender still have same problem

SurferDude41

deaglan169 wrote: »

seems to be common problem with vags this winter, im having similar problems car heats to 90c then cools down to about 75c and remains there seems to be when im stoped it drops, some times it only rises to about 75c and sits there, i had timing belt and water pump done so i got mechanic to replace thermostat when he was at it and i also changed the coolant/temp sender still have same problem

Unless you are driving, a diesel car's temperature gauge will drop below 90 degrees fairly quickly anyway.

A petrol car can usually reach 90 degrees, if left to idle for 10 to 15 minutes. (From Cold)
You could leave a diesel car ldeling all day, and it would never warm up.

deaglan169

i understand that but when you get a diesel up to temp it should stay there for the duration of your drive

SurferDude41

No, the temprature gauge should sit at 12 O clock. pointing straight up at the sky, when you are driving along between 40- 60 Mph at around 2-3 thousand RPM.


I drive a Skoda Octavia Tdi, same engine as a VW, and my temp gauge sits at 12 O clock, unless im pulled in or sitting in traffic.
When I am either sitting in traffic, or pulled in to the side of the road with the engine at idle speed (900 RPM)
At idle, the temperature gauge will drop to 75 degrees.

This is normal, with a diesel car.

deaglan169

SurferDude41 wrote: »

No, the temprature gauge should sit at 12 O clock. pointing straight up at the sky, when you are driving along between 40- 60 Mph at around 2-3 thousand RPM.


I drive a Skoda Octavia Tdi, same engine as a VW, and my temp gauge sits at 12 O clock, unless im pulled in or sitting in traffic.
When I am either sitting in traffic, or pulled in to the side of the road with the engine at idle speed (900 RPM)
At idle, the temperature gauge will drop to 75 degrees.

This is normal, with a diesel car.

in the four years i have owned my seat leon it has never done this untill recently, it would take a while to reach 12 o clock as is normal then sit there but if i stoped and left car idling at traffic lights/jam etc it would never drop below 12. even if parked car up and got back into it half hour later it would have dropped very little maybe 10 o clock position, the symptoms i have mentioned suggest a dodgy thermostat but i have replaced mine unless replacement is dodgy also

SurferDude41

Could be a dodgy thermo-switch.
This activates the radiator cooling fan. Perhaps your fan is cutting in too early, causing the engine to cool down too much.

Did the problem start, when the thermostat was replaced?

Otherwise maybe an airlock, in the cooling system (Try Bleeding it)
Get a Haynes Manual, only €25, will be a good investment.

Your mechanic could have fitted the wrong spec thermostat???

deaglan169

SurferDude41 wrote: »

Could be a dodgy thermo-switch.
This activates the radiator cooling fan. Perhaps your fan is cutting in too early, causing the engine to cool down too much.

Did the problem start, when the thermostat was replaced?

Otherwise maybe an airlock, in the cooling system (Try Bleeding it)
Get a Haynes Manual, only €25, will be a good investment.

Your mechanic could have fitted the wrong spec thermostat???

ill check the thermo-switch tomorrow could be it, no thermostat is defo the correct one got it myself, also ill try bleeding it maybe mechanic didnt bother.thanks

greenermetals

thanks all for the help folks! the thermostat has been changed on it yesterday, and no change. read on the internet that perhaps flushing the coolant system and trying to get some of the gunk out of the heater matrix might help. Does anyone know anything about that? anybody do it with any success? What about this valve surferdude? where would i find it? Other internet searches have said it could be either the blender doors (which by all accounts are even harder to get at than the matrix) or a blocked pollen filter (i dont think it is as the blowers are going full blast)

greenermetals

the engine is running at normal temp. too, its at 12 0 clock

Tea drinker

greenermetals wrote: »

the engine is running at normal temp. too, its at 12 0 clock

Think the sensor is supposed to show it "at 12 o' clock" , even if the temp is not exactly that. It stops people obsessing about the temp or thinking there is a problem , and only if it varies outside a wider range is the change reflected on the dash

bryaner

With regards to the water pump, I have come across this once where the fins on the impeller of the pump had corroded away and the coolant was not circulating properly leaving the matrix without a constant feed of hot coolant.

That was once in 20 years but you never know..

Tea drinker

bryaner wrote: »

With regards to the water pump, I have come across this once where the fins on the impeller of the pump had corroded away and the coolant was not circulating properly leaving the matrix without a constant feed of hot coolant.

That was once in 20 years but you never know..

interesting point, I heard a few water pumps on passats failed as the impeller was spinning on the shaft, so same symptoms

greenermetals

SurferDude41 wrote: »

Could be a dodgy thermo-switch.
This activates the radiator cooling fan. Perhaps your fan is cutting in too early, causing the engine to cool down too much.

Did the problem start, when the thermostat was replaced?

Otherwise maybe an airlock, in the cooling system (Try Bleeding it)
Get a Haynes Manual, only €25, will be a good investment.

Your mechanic could have fitted the wrong spec thermostat???

the problem predates the thermostat. Think the cheapest option would be to flush the cooling system thereby flushing any crap out of matrix and then making sure that its put back in without any airlocks. Then he'll know if its definately the pump or not. What do youse think of this idea?

greenermetals

or maybe the thermo switch before the pump?