WOW! Sounds like my Scirocco when I first got it. I don't even know where to tell you to start but either way good luck
(semi) Random Thoughts:
- Coolant Expansion Tanks, Caps, and Fittings can leak, but not be noticeable when unpressurized.
- Having approx 15psi in the Coolant System is necessary tot e design to operate correctly.
- Heater Core must have coolant flowing through it during bubble purging, air burping, re-filling procedures.
It is , ness, in fact counter-productive to turn on the HVAC FAN during this, you just want the heater's Coolant Valve OPEN.
Note: based on the A2's I campaigned, I always had coolant flowing through the little hose and into the Coolant Exp Bottle, when the Engine was running. This may not be the case w/ A1 chassis 16vs, I wouldn't mind somebody touching on this-
Does a properly working Scirocco 16v have constant coolant flow into and through the Expansion Tank when the Motor is Running?
If it were me, I would check your expansion tank, cap, and coolant sensor like TBerk said. My engine was running hot as well and I did a lot of the things you tried. It seemed like my system was holding pressure, but I replaced my coolant sensor because it didn't work, and my temp on the gauge dropped to a more comfortable level. Then I decided to change the cap because I had a new one sitting around in one of my parts bin, and low and behold my temps dropped to halfway in slow traffic and loooooong traffic lights.
There's a "Coolant Level Sender". It's on top of the tank and it's plastic. The one on the side of the engine is an "Engine Temp sender" and goes to the ECU. The one on the front flange is the "Coolant Temp Sender" and sends temps back to guage cluster.
These are the one's that crack. All this one does is warn you if you have low coolant. If you have coolant around this, chances are it's either cracked or has a bad seal.
Last edited by definition56; 09-08-2012 at 12:38 PM.
I think the tank is the issue. Specifically, I think the threads for the coolant level sensor are shot.
I installed the new sensor, still got some leaking around it after a healthy drive. I tightened it a little more and *POP* the sensor was loose again having 'skipped' the threads. I don't think I can tighten it enough without it 'skipping' the threads like that so it can get the proper seal. Hell, I'm tempted to silicone it in there and just replace the whole tank and sensor should they go again.
Ran hot on the drive home again today. Sooo frustrated.
Dumb question: could the iridium spark plugs I installed be adding to the problem? I highly doubt it, but the car didn't start running hot until I replaced the plugs. I did a search and the 3 electrode plugs appear to be the preferred ones, not the iridium.
I would definitely get a new tank and coolant level sensor.....and as TBerk mentioned, get rid of those plugs. They burn hotter than copper or silver plugs. Stick with an oem grade like the NGK #BKUR7ET . The Nology silvers are nice plugs as well (basically the same as the old Beru Silverstone plug)
Here's my two cents. If your scirocco is overheating its probably because the previous owner topped it off with regular green anti-freeze from the auto part store. When you do this, a crusty precipitate forms and clogs everything including your block. I had overheating issues with my 16v until I had the block hot tanked at the machine shop before boring/etc. I too had replaced everything else before.
Oh my other cent. The fan switch is in the radiator. The fan turns on when the radiator gets hot not the engine. If you have little coolant flow through the radiator for whatever reason, it won't get hot and the an wont come on. Do you have ac?
You may also want to check your ignition timing. If its too retarded you will run hotter. Plugs will not make your engine in hotter. The temperature of a plug refers to how hot the tip of the plug runs. Hotter plugs sink less heat into the head and therefore run hotter at the tip. Colder plugs have a greater path for heat to leave the plug into the head. Your hunch is right. It makes no difference.
Lastly the flow into the reservoir tank is irrelevant. Many here have eliminated the reservoir tank altogether and run just fine.
I wish I had a definite solution but a clogged block is all I can add.
My coolant level sender somehow leaked where the contacts are in the center of the sender which caused the pins on that plug to be jumped so even when my coolant was low I didn't get any warning... Then right after I replaced it, my expansion tank cracked so I had boiling water spewing out onto my strut tower...
After reading the post below, I think this all boils down to being off by one tooth on my replaced timing belt:
Grrrr. Drove the car today. Ran fine in the morning. Drove out to Euclid Foreign on 271/90, also ran great and coooool (halfway on temp gauge). Driving home in city traffic it ran hot (temp gauge at line near top). Closer to home it crept above the line, but no blinky light. At a stop I turned the car off, HEARD LOTS OF GURGLING, started the car and the light started flashing. I wasn't seeing any steam so I kept going (was really close to home). Got home, opened the hood and it boiled over w steam and everything. THE FAN NEVER CAME ON. (Car has new rad and fan switch and fan has come on before, heat was on the entire drive). Hose at top of radiator is hot. I let it cool a few minutes, turned car back on, turned on heat and fan should have come on, but didnt. Any thoughts?
Replaced the plugs w proper Bosch plugs. Took car for a spin: ran cool-ish (just below 8 o'clock line) then blinking light and temp DROPPED to just above the mid point mark. Poltergeist perhaps?
Pulled coolant cap off, some bubbling/burping of air. Coolant has now dropped CONSIDERABLY.
Your post above says unequivocally that the car was way hot and the fan wasn't running, ergo, at that point it time (perhaps not all the time), there was a failure point somewhere in the fan circuit, which merits investigation.
All of the other things you're doing are good things, but IMO they represent shots in the dark, so to speak. I think you'll find the repair less frustrating (I'm quoting your "grrrr" ) if you approach the problem methodically.
Here is what I am doing just to drive my Scirocco until I track down that coolant leak:
1. Disconnect AC compressor and the AC idle boost solenoid.
Now when I turn on the AC only the radiator fan comes on.
2. Replace the thermostat with an old one, with the entire 'core' removed, leaving the outer ring.
(can't just assemble with no thermostat).
Check the circuit at the fan switch - jumper from red to either of the other two should turn on fan.
Good connection to the switch?.
I was fooled by the small recovery hose - it would allow coolant to flow when filling, but no flow when running. A piece of RTV was acting like a one-way valve in the hose.
Next up is a full back flush.
I finally just replaced the recovery tank with one with no coolant level sender.
echassin, I'm totally taking shots in the dark with this. I'm not proud of that, and no, it's not the best way to attack the problems, but I'm trying to do this on my own. I love to figure out problems and fix them. I'm a little stubborn in this regard. While my 'progress' thread (in my signature) points out, I've never done much work on cars, but I am mechanically inclined. So I'm just plugging away at it til I figure it all out.
And before I forget, thanks to everyone here for the support and feedback. I was hesitant to post my dumb questions here after seeing some posts in the MKIV and MKV forums where the members were....less than helpful. I really appreciate all your help.
Does a VW professional shop have special tools? Possibly a pump to force air out instead of just waiting and bleeding all day. I tried a vacuum pump on that little line to the tank, but I can't say it helped except to drench the pump with coolant.
With no radiator fan running due my oversight, the car only overheated after getting up to speed entering the Interstate Highway System.
Last edited by MacGruber; 10-07-2012 at 08:08 PM.
I think the fan run-on switch is bad. Car ran hot and boiled over again today. Fan did not come on. I checked the fuse, then was pulling the fan relay and it was pretty badly corroded. When iIwas removing it the cover actually came off exposing the innards allowing me to trip the switch and the fan ran. So I know the fan works. I'll pick up a new relay this week and see if that solves it.
FYI when I fill my system with coolant there is little to no burping required. I let it idle with the cap on till the fans come on then let it cool down, top it off and that's it.
You said it overheated getting on the interstate? Wouldn't that suggest that it wasn't due to the fan not working? Either way you have to sort that out for sure. Hey does your fan shroud have those rubber flaps installed? Do they seal tight against it when the fan comes on?
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I just went through this same nightmare in my cabrio last summer. New radiator, thermostat, coolant, fan relay, ALL new sensors for anything related to temperature.
After all was said and done I installed one of the el cheapo manual temp gauges in line of the radiator hose right off the block...to my shock and horror...the gauge never ever read higher then normal operating temperature even when the needle in the dash was pegged and the light was flashing.
Bust guess is something in my instrument cluster is fubar. I got another one to try but never have put it in. Car still running great with gauges freaking out almost every time I drive it months later.
It's the most expensive/annoying mess I ever dealt with to accomplish nothing.
Good luck, and don't rule out the weird stuff....
Side note: picking up the new fan run-on relay tonight. I'll throw it in and take the car for a spin. I don't want to jinx things, but many signs point to the issue being a semi-functioning relay (works some times, not all the time). Fingers: crossed.
There isn't really a Run On Relay as such. The main Curcuit in the VW Radiator Fan system goes from
- Battery through
- Thermo-switch (in Radiator) to
- Relay to
- Fan and back again to
(Cars w/ A/C get a secondary circuit to turn on the Fan when the A/C is activated.
If you have Hot Coolant in the Radiator then the Fan should run due to that Thermoswitch. It'll run intendant of the state of the car running or not, Ign Switch On or not.
Easy way to see if the System is working is to pull the wire plug off the Radiator's Thermoswitch and jumper the two ( or two of the three in a dual speed fan setup), the Fan should run. Bad Thermoswitch.
(Or you aren't flowing hot enough coolant past it in the 1st place...)
refers to my lol experience, not silverspeedbuggy's. Made it home with radiator fan on via the AC switch as described.You said it overheated getting on the interstate?
The two speed fan switch just comes on at two different temperatures - it will run at high speed anytime if hot enough.
Good point about the rubber flaps - it they are missing the fan can just suck air in from the engine compartment instead of via the radiator.