Cooling a 2.0 16v - rad fan (new switch fitted..)

[KipVR 1]

The water pump is about a year and a half old

 

Sounds like it wouldn't be that after all then, you could check the flow is unrestricted by connecting it up to a garden hose and running water through the system (without the thermostat in), just to make sure though, run some rad flush through the system beforehand, you'd be suprised how dirty it gets.

[Jim 2]

I'm fairly sure there is no muck in the system though mate. I'm not lying when I say I've changed the coolant on my car at least 10 times in the last 2 years what with various jobs such as 2 radiators, and so forth. Every time the coolant comes out it's still totally clear and pink from the last time I changed it :(

[davidwort 0]

dodgy dash gauge? I assume the dash all works on 12v, in which case it should be possible to directly wire a second hand temp guage module to the senders to compare readings.

I think I have a VDO water temp gauge somewhere, definately got a spare passat dash and that has the same water temp unit as the C, if you don't get it sorted before, I'll bring it along to a meet. Need to rig up something similar anyway as I occasionally get a spike on the gauge as the engine is warming up which is far too fast to be a genuine temperature increase, it drops back down almost instantly too, another weird one :)

[Jim 2]

Would be up for a bit of under bonnet poking about at the next meet, David. Definately worth a try to see if we can work out whether the gauges / senders are telling lies.

 

The oil temp one has probably never been changed so could be over-reading as well!

 

Folks on club GTI are suggesting I get the fuel mixture / timing checked as if it's running lean it can cause an increase in temperatures?

[Henny 0]

if there was a blockage in the oil cooler, your oil temps would go up faster/higher than normal, but your water temp shouldn't go up much more, and your fan would kick in to keep the coolant temps down... the oil cooler is not in the main route for the coolant, so the coolant would simply bypass it should it become blocked...

 

Get your fuel pressure checked... I noticed on H-YYU that she was getting hotter than normal a few weeks before she came off the road due to a dead headgasket... that turned out to be a weak fuel pump causing the engine to run lean and therefore very, very hot... :(

 

I'd also be very tempted to stick a new water pump on to be honest...

 

Just a quick question... does the radiator fan ever come on? may be worth checking that it is working on both speeds and spins freely... could be something as simple as the over-run/first speed fuse having blown... :wink:

[Jim 2]

Can't get used to you posting on here again Henny! :)

 

Yeah the fan does eventually come on when the car seems to be really hot. Whilst putting the car away after the trip to Stealth the other day I stuck my ear to the grille and could hear it whirring away on lowest speed. I've bridged the pins on the plug so know that the fan does work on both speeds.

 

Fuel pressure I'd be interested to get checked. Just means more trips to Stealth and more bills but I'll pay whatever I have to to get my car running properly.

[mrbeige 0]

What's interesting is that the fan doesn't come on that often, which given that the rad switch, rad, thermostat are all new suggests that the rad just isn't getting hot enough to warrant the fan coming on in the first place. I really think it's the sensors and/or instrument cluster giving you duff info.....

 

 

...if not then just drop a 20vt in there and be done with it ;)

[Jim 2]

My thought it still on the circulation of the coolant. The clocks display the temperature of the coolant from the side of the block and the rad fan switch is right at the bottom of the radiator.. I can't help but think that, as you say Stu, the coolant in the radiator is just cool but for some reason the coolant in the block isn't and the system just isn't circulating the cooled coolant properly.

 

Or, as you say, sensors are lying..

[vwdeviant 0]

MAd Q but know anyone with an I/R temp meter? The kind you just point at stuff?

 

Could be worth checking hoses etc with one of those too, that way you're not relying on possibbly duff sensors/guages!

[Jim 2]

I think Eric / Tempest has one.. will have to bug him about it!

[Supercharged 2]

Might be worth buying the metal water pipes mate while you still can, they rust internally and this restricts flow...

 

Could also be headgasket starting to fail I suppose but I would think you'd see an excess in pressure in the cooling system.

[Jim 2]

Where do the metal water pipes run mate? I've never seen or been shown them before!

[mrbeige 0]

IIRC, there is one that runs from the RHS of the block round to the front behind the oil filter. It connect to the odd shaped T piece that connects the front top rad outlet to the pump and heat exchanger.....clear as mud....could well be blocked, they do rust like a rusty thing

[Jim 2]

Dread to think what they cost from VAG...

[vwdeviant 0]

 

Just for you Jim!

 

IIRC they aren't massivly expensive... had this with teh 8v GTi Engine in the Scirocco a few years ago!

[davidwort 0]

here we go:

pipe.jpg[/attachment:16ezja8f]

:shock: :lol: it's OK I think my price file is corrupt.

[Jim 2]

Zoiks!!

[mrbeige 0]

They are never that much?????? :shock:

[vwdeviant 0]

Hang on I'll ask a VAG-Mole.. :norty:

[Pickard1 0]

Just dropped by and read all of this.

 

I see that when you bridged the connector you only got the fan to spin on one speed as it sparked on the other. Did you ever repeat this test and have confirmed fan spinnage on both bridging configurations.

 

In this thread I used some spade connectors to stop the sparks/burnt hands!

 

viewtopic.php?f=1&t=48405&p=573374#p573374

[Jim 2]

Don't remember actually mate. Will have to go out and revisit that one.. don't remeber if I ever got it running on both speeds!

[Purple Tom 0]

Jim,

 

I know its been a little while since you posted on this thread, but I just wanted to add my thoughts into the equation. I am having similar 'issues' with my 2.0 8V (ADY), in that the temperature gauge happily climbs up to 110ºc on the gauge before the fan comes on, and then it only comes on on the slower speed. The temperature falls quite nicely to about 100º on the gauge, the fan turns off, and then the same thing happens again. Oil temps vary between 98º and 112º after a hard drive. The car also sits at about 95º on the gauge when cruising at motorway speeds.

 

So far I have replaced the fan switch, the coolant temperature sensor, expansion tank (mk4 item), a couple of metal pipes, the plastic housing on the head and the thermostat, all with genuine VW items over the last 8 months or so. The radiator is still the original, as is the water pump, oil cooler/heat exchanger and heater matrix. The coolant is new, stays clear and doesn't ever require filling up. Obviously the inidicated temperature is high, just like yours...

 

However...

 

I've been thinking a little bit of the layout of the coolant temperature sensors on my engine, and also from looking at Etka it would appear that the 16V is the same. Look at where the coolant temperature gauge takes its reading from - it is the plastic housing where the coolant exits the cylinder head before making its way along the top hose to the radiator. This is the hottest part of the engine and where the coolant its going to be at its hottest before returning to the rad....

 

Then look at where the fan switch is located - right at the bottom of the radiator where the coolant is pretty much going to be at its lowest possible temperature before going into back into the engine. The standard three speed fan switch is designed to switch the slower speed on at 95º and off at 84º, and the fast speed comes on at 102º and off at 91º. So, effectively, if your fan is coming on at the slower speed then it means that the coolant temperature in the radiator around the fan switch is something along the lines of 95º which is a whole 15º (ish) lower than the indicated gauge temperature!

 

My thinking is that the indicated engine coolant temperature on the gauge IS accurate and the coolant temperature is approaching 110º when it exits the engine, but that doesn't mean that the coolant temperature through the whole system is at that temperature. In fact, the coolant entering the engine is likely to be at a temperature of around 85-90º, which is plenty cool enough!

 

I know for a fact that my 2 speed fan works properly, I fitted it myself (for some reason my car had a single speed fan yet had all the wiring necessary for a 2-speed fan so it made sense to fit a 2-speed system!), yet even in the 30º+ heat that we had 2 weeks ago the faster speed didn't come on, the slow speed was plenty to bring the temperature down to reasonable levels on the gauge again. My car runs fine and there is no signs of any temperature related issues. Also remember that modern cars temperatures can vary by as much as 20-30º in normal use, but as long as the temperature is classed as 'within tolerance' by the ECU the gauge will sit bang in the middle! According to the Corrado owners manual the operating temperatures on the gauge can get pretty high when working hard too...

 

Sorry if this has already been covered, and sorry if I'm preaching to the converted, but I thought I'd just add my findings into the mix for you :) I just think that maybe you've got nothing to worry about...

 

Tom

[Supercharged 2]

Tom, can you get both speeds to activate by unplugging the switch wiring and bridging them??

 

Just wondering if the wiring on the plug is maybe wrong etc...

[Purple Tom 0]

Yup, both speeds work fine when bridging, and I even tested the switch before fitting to ensure continuity when getting up to high temperatures...

[davidwort 0]

I thought Eric had a IR temp reader and Jim was going to try, or did try this on his engine?

I really must try the one out my dads garage have, we used it once on the engine block when I was worried about oil temps and it confirmed my 16v MFA oil temp reading was pretty much bang on, out of interest I have an oil filter bracket from a SEAT on my car which came with another oil temp sender on the top, instead of the blank that 2L Corrados have, same sender as the one on the back of the 16v head but in the filter position it read a couple of degrees lower all the time.

Next time I get the chance I'll take IR readings all around the engine bay and cooling system with/without the rad fan on, will be interesting to see how it varies, well, interesting in a dull sort of way :lol: