VR6 Very Slow Warmup - Help please

[Projek01]

Hello guys,

This is not the first time that one of my car has had problems warming up but this is the first time I could not remedy it. The ambient temperature is falling below freezing now and I am having a hard time hitting operating temp. My commute to work is about a 15min-20min drive going 100 kph for about 85% of the drive. It was around freezing today and I barely hit operating temp today even with a 5min warm up on the driveway. When it hits about -20C, I am forced to warm it for 10min to get enough heat to keep the windows from freezing. This is a huge waste of gas and bad for the environment. Scaling looked quite significant before I did the acid soak. Rinsed all of the scaling out of there and soaked it one more time for good measure.

Things I have tried so far:

New Mahle thermostat (twice)
Citric acid flush of the cooling system (twice)
New water pump
New coolant after really cleaning out the system with de-ionized water mixed 60:40 coolant:water

These things have fixed my problems on my Honda and Toyota in the past. I am thinking that the electric re-circulation pump or check valves could be suspect but I do not fully understand the system. Do you guys have any suggestions?

Thanks in advance
Anthony

[ShermanEF9]

usually a failure of any of those systems would cause overheating problems, even in this weather. have you tried the ol' shove cardboard infront of the rad yet?

[jacky4566]

Looks like my post didn't get in when beyond crashed.

Did you test the new thermostat personally before installation? I know your not dumb but maybe you installed it backwards?

Next i would check all the thermo sensors and connectors, you might be running really rich and not warming up.

[revelations]

Dumb question - but are you sure its not a heater core problem?

['93 SR-V]

Seems like it could be the thermostat even though you've tried that. Have you tried an OEM thermostat? I've not had good luck with aftermarket t-stats myself.

[jacky4566]

Originally posted by revelations
Dumb question - but are you sure its not a heater core problem?

Good point. Is the engine actually cold or did your heater core fail.

[Projek01]

thanks for the replies guys.

I am looking at the temp reading on my cluster and it seems cold even there. Eventually, it does warm up and I get good heat after a drive longer than 30 min. I think that would rule out a plugged heater core.

I don't think the thermostat can be installed backwards on this engine but it would likely overheat if it was i believe. The Mahle one should be OEM without the VW box but I can't say for sure. If all else fails, maybe I should try one from VW.

The coolant flows through a heat exchanger to warm up the DSG oil too. Maybe there are too many things the engine is trying to warm up at once.

Another think I checked was for any codes using VCDS. All is normal there.

[jacky4566]

Another thing to consider. Which Mahle Thermostat did you buy? I see they make a few different 71C(low temp) and 80C(OEM). Maybe you got the low temp one?

[Projek01]

I bought the OEM temp 80C for sure.

Here is a simplified schematic of the cooling system. I am trying to understand if stuck open/closed check values could be something that would cause this. The directions of the arrows is throwing me off when I try to follow the paths.

[Ca_Silvia13]

Originally posted by ShermanEF9
usually a failure of any of those systems would cause overheating problems, even in this weather. have you tried the ol' shove cardboard infront of the rad yet?

Often the best solution is the easiest. My old Golf was the same way in college.

[jacky4566]

Originally posted by Projek01
I bought the OEM temp 80C for sure.

Here is a simplified schematic of the cooling system. I am trying to understand if stuck open/closed check values could be something that would cause this. The directions of the arrows is throwing me off when I try to follow the paths.

OMG you poor bastard. Leave it to VW to have such a complicated coolant system. Ya check those check valves, could be some backflow happening.

[revelations]

Yea definitely check those check valves and perhaps even add a flushing tee kit with a garden hose and do that for good measure. Sounds like something might be plugged.

[Projek01]

Yeah, I will have to check those valves. Hopefully they just need a cleaning if they are indeed clogged. At $60USD a pop, I don't want to blindly replace them.

Thanks guys for the tips

[carson blocks]

That's an absolutely terrible diagram for the cooling system.

[Projek01]

I did some poking around and the check valves seem to be working fine (based on temperature). However, from the temperature readings off of the hoses (approx using infrared thermometer) it seems like flow through the V51 coolant pump is going backwards. Does anyone know if that is possible?

These temperatures were taken after a short drive. Engine is around 70C and the tranny should be cold.

Thanks