Bolts for turbo and manifolds, was Turbo cooling fan?

Post by **Macflai** » 17 Jul 2007, 21:23

Well dismantling the turbo from my van I have seen something like a heat extractor, the "mouth" of this thing is over the turbo and is connected through a flexible hose to an electric motor. Invents. This vans have a lot of invents!
I think it works like the radiator fan, a heat sensor connecting to the electric motor? Is that right? Do you think they work?
I ask because when I fixed the gearbox I didn't install all the covers around the engine, only installed the engine undercover (heavy one).

Post by **andysimpson** » 17 Jul 2007, 21:57

The cooler works really well the problem is the switch that brings it on, vw were lazy/penny pinching with it. It measures coolant temp which os not a good way of doing it, mine measures manifold temp.

Post by **Russel** » 18 Jul 2007, 06:04

It is controled by the same sencor and relay as the aux.water pump.

Post by **Macflai** » 18 Jul 2007, 09:24

Ow! okay then but... The aux water pump has been disconnected due a broken sensor... so I made the whole trip to England, Ireland and Europe and back to Canaries with that thing broken... and we had no problems, always the temp was right

I am a lucky guy I think

Post by **HarryMann** » 18 Jul 2007, 09:36

The aux water pump has been disconnected due a broken sensor... so I made the whole trip to England, Ireland and Europe and back to Canaries with that thing broken... and we had no problems, always the temp was right Wink

Mac, the aux water pump doesn't control water temperature... in fact if its broken water temp will be lower if anything.

It circulates water through the oil-heat exchanger to first heat up and then cool the oil... but only when things get very hot (see Andy Simpson's comment about the sensor switch)

It would be oil temp that would suffer, and without an oil temp gauge, you wouldn't know... unless it gets very hot and the buzzer goes off.

The aux pumps often don't work on older vehicles (all are now old) - the turbo cooling fan also fails due to the same switching system being used. Sometimes the whole turbo blower has not been replaced and is missing.
The aux. water pumps are about £60 from VW

Post by **Macflai** » 18 Jul 2007, 09:51

Now I am thinking about dismantling the heat extractor and check if the engine runs well here. Usually temps are something like 25ºC the most of the year but we are getting 30ºC and a bit more in the south of the island, Playa del Ingles and Maspalomas where the thermometer reaches 35ºC or 36ºC...

Place where I live... northeast.

Check it if you want on Google Earth... 28° 3'6.36"N 15°27'59.37"O

Post by **HarryMann** » 18 Jul 2007, 10:13

28° 3'6.36"N 15°27'59.37"W will get it.

Doesn't seem to like O for West on our Google Earth

...looks a very relaxed and pretty place from here. Some nice panormas around the town...

Post by **dave friday** » 18 Jul 2007, 12:00

Andy,what sensor have you used and where have you fitted it?.
ta.

Post by **peasant** » 18 Jul 2007, 12:44

AFAIK the aux pump and the fan to cool the turbo only come on when it's pretty much too late and only when the engine is off.

When the engine is off and the temp sensor measures above 104 degrees coolant temperature, not only does the radiator fan engage, but the aux water pump pumps some water through the block to remove excess heat and the fan blows air on the turbo to cool it down.

If you drive your van properly and don't shut it down sizzling hot, neither should come on.

The pump and fan also get a quick impulse to run on startup to stop them from seizing.

But, as I said ...AFAIK ...and I don't know everything

Post by **HarryMann** » 18 Jul 2007, 16:29

I think you're about on the mark Peasant

Doubt if anyone really wrote a proper book on the deeper and darker mysteries of some T25 fitments...

Post by **dave friday** » 18 Jul 2007, 17:24

i've taken to turning the heater on just before[2 min's] switching off, then the 1st stage fan comes on for about 1 min, the aux water pump and the blower are allready on and sometimes stay on for as long as 10 mins!!.its a bit tricky treating the van gently as the road home is nearly allways up hill.

Post by **Simon Baxter** » 18 Jul 2007, 18:44

fan is there to cool the turbo (obviosuly) and as stated they generally run when the engine is off.
When you turn an engine off, it actually gets hotter as heat soak, well, soaks away. You stopped the engine so it has no pump.
So, you knock the engine off, the belt driven pump is no longer moving water so the engine gets hot, the aux water pump will switch on and start moving coolant around to try to lower the coolant temps.

then, you knocked the engine off, the oil in the turbo will also get hotter, the fan is there to try to cool the turbo to stop oil getting baked in the bearing housing.
On similarly engined contempory Golf, passat etc they have a water cooled turbo, with water pipes running too and from the turbo switched in a similar fashion to again lower the temp of the oil in the turbo once the engine is off to stop coking of the bearings.

Post by **Macflai** » 18 Jul 2007, 19:21

Ok I had a Land Rover Defender and has no that invent but the turbo always worked nice... and no problems... if I dismantle that heat extractor and no install it anymore, will the turbo have a shorter life?

Post by **andysimpson** » 18 Jul 2007, 20:59

Turbos on almost every engine has a drain at 6 o clock so all the runs out and does not get baked, on a t25 the drain is about half past four and oil gets trapped in the turbo where it bakes and turns to a solid eventually restricting oil flow and turbo dies. Even letting it idle for 10 mins your still looking at over 100c turbo temp.

Post by **Simon Baxter** » 18 Jul 2007, 21:51

andysimpson wrote:Turbos on almost every engine has a drain at 6 o clock so all the runs out and does not get baked, on a t25 the drain is about half past four and oil gets trapped in the turbo where it bakes and turns to a solid eventually restricting oil flow and turbo dies. Even letting it idle for 10 mins your still looking at over 100c turbo temp.

I often wonder about using a banjo bolt and a flexy hose to feed the turbo and try to get it to sit with the oil feed and returns closer to the vertical.

Infact, when i actually get time to build that AAZ up i may just do that.