VR Overheating

[Critical_Mass 10]

Hi all,

 

Good start to a monday morning - Got a couple miles away from work this morning (20 miles in total). Water temp light starts to flash and the water temp on the dash starts to rise. I ended up hitting traffic, which in a way was a good thing as it was stood for a while between creepign forward - i was able to turn the engine off and let the fans cool the engine down. There was also no steam - water was still full when i looked under bonnet.

 

Though clearly there's an issue here. The only thing surely it could be is that the fans arent working - ive been having issues with the fans for a while, but mainly when the ignition was switched off.

 

Can anyone confirm if this is the likely cause. Also which sensors control the fans?

 

Cheers all.

[fla 9]

Gaz, do the fans come on at all? I would check the rad sensor down by the battery. screws directly into the radiator. In fact take the connector off the sensor and bridge the connections. Speed 1 should come on.

[Kevin Bacon 5]

From memory.....

 

Speed 1 - Radiator sender - White/red wire

Speed 2 - Radiator sender - Red/black wire

Speed 3 - Black sender in Theromstat housing

 

Fan after-run and aux water pump:

 

Pins 1 & 4 - Yellow sender in thermostat housing

 

Dash guage:

 

Pins 2 & 3 - Yellow sender in thermostat housing

 

All of these connections, except yellow 2&3 go to the Fan control unit.

 

If the engine is overheating that quickly this time of year, it's a good sign of a thermostat which is jammed shut.

[fla 9]

you can always rely on Fishman to come up with the specifics even though he's progressed to an R32!

[Kevin Bacon 5]

I still use much of the 12V stuff, so it's still in memory :D

[Critical_Mass 10]

Thansk for the replies guys.

 

TBH i dont notice the fans coming on unless i switch the engine off..... which always appears to come on these days. Would this suggest the yellow temp sensor is fine and the rad one is buggered?

 

I'll check the bottom hoses is hot to rule out the thermostat. Im getting hot air in the cab if thats any indication.

 

---------- Post added at 02:17 PM ---------- Previous post was at 12:35 PM ----------

 

Right, been able to do a bit of checking. Left the car to cool down a little, then ran it up to temp the car went up to 110 but then i switched the car off and left it for a couple of mins. THen back on again. The temp (on the guage) had dropped to about 80 - so we can assume thats wrong. Running it back up to temp no fans came on and it went to 110 again. Took the cap off the reservoir and although hot it wasnt any hotter than it is when running at normal temp.

 

Also im led to believer if the car over heats there will be steam as water pours out of the reservoir. No such thing happening.

 

So is the gauge wrong or is it actually overheating - as at the mo it doesnt appear to be doing that. This could be why the fans arent coming on.

 

---------- Post added at 02:19 PM ---------- Previous post was at 02:17 PM ----------

 

Oh and the thermostate must be working as the bottom hose is hot

[fla 9]

seems like a gauge error, so thats the yellow temp sensor. There is a vent in the side of the header tankthrough which any coolant can bubble out if it gets to that, although the bottle is actually double-skinned so it usually just recirculates.

[Critical_Mass 10]

Yeah im hoping its just the guage. Got one on order, off to pick it up soon and change it... take it from there. This is the last thing i need grrrr ...

[beastie4126 0]

I had exactly the same symptoms with mine a while back that led me to change sensors, expansion tank, flush coolant and so on. it turned out i was barking up the wrong tree completely the culprit turned out to be the plug on the gauges had worked loose. only happened intermittently and no water loss or anything.

 

Thinking about it mine stopped when i turned the lights off as well so must have been shorting somewhere ??

[Kevin Bacon 5]

Sounds like a yellow temp sender fault to me, especially if the fans are coming on without the engine running and it's cold. Since that one sender controls both the guage and the after run fan/pump, it's a good place to start.

[Jon_vr6 1]

Had that on mine when i renewed all the thermostat housing etc, turned out to be the yellow temp sender no problems since

[Critical_Mass 10]

Well just been and changed the yellow temp sender (which are now brown for the record). The fan now seems to work when engine is up to temp - dont recall it doing that for a while. The gauge no longer goes too high and the light no longer comes on. So the panic is king of over.

 

However, that said, with the new sender the gauge hasnt moved off the bottom even after a run. So its gone from one extreme to the other. Tested the plug with a bulb and the gauge did work, just not when its plugged into the sender.... faulty sender i know suspect. So getting another one in to replace it. Though at least it seems the problem has been pinpointed.

 

Can anyone confirm the correct part number for the sender (93 VR)?

 

The sender we got was taken from my reg no. then in turn the chassis number, so it should be correct. I just want to rule out the wrong part number also the fact its brown - was expecting black.

 

Cheers for the responses guys!! :D

Edited February 6, 2012 by Critical_Mass

[Kevin Bacon 5]

However, that said, with the new sender the gauge hasnt moved off the bottom even after a run. So

 

It is cold mate! :D

 

The water sits at 83 deg this time of year on a healthy cooling system, which is also just above the minimum on mine. Takes a while to get there too. I monitor water temp directly from my engine management (blue sender) which is more accurate.

[Critical_Mass 10]

Its not that cold though, surely it would move a little. Seriously it didnt move a tad, not even slightly off the rest. I may plug VAGCOM in and what the reading is

Edited February 6, 2012 by Critical_Mass

[Kevin Bacon 5]

Hmmm, that's not right then. I thought the replacement for the yellow sender was green/yellow? Brown sounds strange. Clearly these senders are calibrated to specific dash guages. Maybe you have a passat one or something. Have you got a multimeter? I've got as spare yellow sender and we can compare the resistance across pins 2 & 3.

 

Yeah VAG-COM the engine coolant measuring block and that is the ACTUAL water temp, regardless of what the dash guage says.

[Critical_Mass 10]

I dont have a multimeter unfortunately. Maybe it is a Passat one, though there's no darn part number on it.

 

Will take a look on vag com and have a search on here.

 

Though as ive just found out, the issue with the after run fans is still there - jsut moved the car literally 10 metres (engine cold) and the after run fan came on :lol:

Edited February 6, 2012 by Critical_Mass

[tonedef 9]

I have a brown sensor in the thermostat housing but it's for the climate control and has two contacts in it. Pins 1 & 4 are a normally closed contact which cut off climate control if temp is too high, pins 2 & 3 are a normally open contact to start fan speed 3 on high temp (must have replaced the black sensor when I originally installed cc, hard to remember!). From Kev's description in post #3 the configuration doesn't sound anything like right for aux pump run on and dash gauge though.

 

As Kev suggests, put a meter across pins 2 & 3 in your brown sensor, it should be an open contact unless you can get the water hot enough at which point it will go directly closed whereas Kev should measure a changing resistance as the temp changes.

 

I also run the standard yellow and blue sensors in the other two fittings for normal Corrado functions.

Edited February 6, 2012 by tonedef

[Critical_Mass 10]

hmmm thats confused things even more as the one i removed was the one with 4 pins and i dont have climate control. The other 2 i have are the blue one (middle) and a black one (far right) both have 2 pins.

 

Do you have the part number for your brown one tonedef. The one ive found using the search is 701 919 369 D and apparently replaced 701 919 369 B. But i dont know the part number of the one ive got - i will find out.

 

How many of the 3 sensors has 4 pins on yours mate?

Edited February 6, 2012 by Critical_Mass

[tonedef 9]

Sorry to have confused the issue, I think the point I'm trying to make is that you shouldn't have a brown sensor unless you've retrofitted climate control!

 

I have the following:

 

Blue sensor, 2 pin, same function as yours.

 

Yellow sensor, 4 pin, again the same function as yours.

 

Brown sensor, 4 pin which replaced the original black 2 pin sensor. Pins 2 & 3 are the original pins for the aux pump/fan run on and pins 1 & 4 are an additional signal to climatronic. It is a p/n 357 919 369 E which I bought in November 2006 for £8.06 +VAT.

 

I hope some of this might help, if I had a spare yellow I'd send it you to see if it fixed the problem.

[Critical_Mass 10]

No worries mate, appreciate the help.

 

That maybe it then, as the fans seem to work now ive replaced the yellow sensor, albeit with the brown. But the brown also has aux pump/fan run on. So obviously the dash doesnt work as the function isnt even present. :lol:

 

Damn suppliers. :lol:

[G-Lad 0]

If you have someone nearby willing to swap for a while so you can test, i'd recommend trying a clock swap. I had an overheat incident which turned out to be most likely due to inefficienct waterpump fins (most missing when unit was removed). After swapping all 3 stat housing sensors plus the housing and the stat, and the rad sensor *and* both waterpumps *and* the control box, I had everything behaving itself but I still didn't get sensible gauge readings again, until I swapped the clocks.

 

It might be overkill, but after all of the above I just didn't trust the gauges!

[Critical_Mass 10]

Well today, it was found that the sensor is the wrong one. Correct one ordered.

 

It should sort the problem. But if it doesnt i hope its not the clocks, i swapped the temp/fuel gauge only a couple of years ago as the previous one was duff too. But im sure the new sensor will will sort

[Critical_Mass 10]

Sorry to continue this guys. Still need some advise.

 

The fans are still coming on each time the ignition is off, based on that ive removed the old sensor on the front of the block and replaced it wtih a new one, albeit incorrect one - this sensor cant be the fault with the fans coming on every time ignition is off. So am i correct in thinking it will be the rad switch in the radiator?

[Jim 2]

It'd be worth replacing that as a matter of course. I also believe the "black box" (circled in the picture attached) has some involvement in or controls the fan system though I can't be more specific. It's only a single connector and a few bolts so might be worth sourcing a known good one off the forum and swapping that too.. I doubt they're available from VW any more and if they would probably cost a fortune!

[Critical_Mass 10]

Cheers Jim, yes i seem to remember that box has something to do with the fans, has fuses in it also doesnt it? (metal strips). I take it the rad switch goes back to the this box?