Hello. My diesel engine is very slow to warm up to operating temperature when driving and the temperature slowly drops when idling. I’ve already replaced the thermostat and the issue persists. It takes more than 10 kilometers for the engine to warm up. I have to say IT IS winter where I live, but my dad also has a car with a 1.9TDI diesel engine and there’s no such problem for him. 2005 Audi A3 103kw 2.0TDI. If anyone needs any further information I will do my best to provide.
Have you checked to see if the glow plugs are operating? Contrary to popular opinion, they don’t always activate only during the morning start. If it’s very cold out they will go on an off throughout the driving cycle.
It sounds like you have a bad thermostat or it was installed backwards. Both can happen. I’d remove it and test in a pan of hot water on the stove to confirm it is bad.
The only reason for a vehicle to warm too slowly is a faulty or missing thermostat.
10 Km seems reasonable, diesel engines don’t generate much heat. Using the heater while idling will cool the engine. Some diesel cars have supplemental heaters to warm the coolant.
Good ideas above. Also make sure the engine cooling fans are only turning on when they should, which is usually only during long idles or stop and go traffic. Are you making this slow-warm-up determination by how long it takes to get heat from the passenger compartment heater, or by looking at the coolant temp gauge? You say your dad has a similar car with a similar engine. Is one a turbo design and the other not?
Our diesel school buses would not warm up at idle enough to defrost the windows even when our mechanics started them 1’2 hour before we cam in. They finally installed block hearers and plug ins at every parking space. Good thing they did. We were violating to law by letting them idle more than 3 minutes.
I had a 60 mile commute with my diesel and in the winter time it could take half of that to fully warm up. Diesels run loose and don’t generate a lot of friction. I always had to put cardboard in front of the radiator in the winter.
I remember doing that with some of the diesels I drove from the 50s to the mid 80s modals but didn’t have that problem with the newer ones I never had a car with a diesel engine I would think by the 2000s they would be much more improved in that regard.
here’s something to consider . . .
Maybe we’re making something out of nothing
OP didn’t mention a check engine light on or a P0128 code or anything like that
Maybe everything’s operating within normal parameters . . . or good enough to not generate that or a similar code