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Lemon Lupo - smokin'

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So, having put it all back together again, I had a look at the thermostat 20210417_145702.thumb.jpg.f2388b246835a782590a85e8508ba7e1.jpg

One was the current one, one was new a few months ago. Stuck them in boiling water


Ah. Only one pushes the pin out initially, although the other one did eventually but not to the same extent. 

Fitted the one that seemed to work, despite running it under the cold tap the pin didn't go all the way back in. This time I could feel I was compressing the spring in the 'stat when I was bolting the cover up. 

Initially all seemed well, warmed up at a sensible rate, however the rad hoses seemed to get warm earlier than I'd expect. Got to 90 and stayed there for a while, then suddenly shot up to 110 and brought the warning light on. 

The hoses don't feel overly hot to me, so I think it's one of two things -

1) cheap thermostat is shit and doesn't open or stay open, so the coolant in the head gets too hot

2 cheap temp sensor I fitted is telling lies

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As the VW dealer I used to work at is moments from where I drop the mrs to work, I thought I'd save some messing about and order a gen-u-ine thermostat. I expected £10-15 for the privilege, but 35 beer tokens is a bit steep for a very simple part. Of course I could order one without the seal for just £28...

£7 for a poxy rubber o-ring! Probably all made by the same people anyway

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Forgive me if this is a silly question but did you not replace the egr valve? 

If you did and used Silicone or any other type of sealant could you have maybe inadvertently blocked the water chanel in the head?? Silly suggestion I know but worth asking. 

Maybe also worth checking is that the radiator isn't blocked and easy enough to do. 

A little odd that it would just decide to just start to overheat suddenly if you didn't really disturb the coolant system. The 1.0 mpi AUC is a pretty robust engine and fairly simple.

Could you maybe bypass the thermostat or run without it fitted for test purposes before laying out a daft amount on a replacement unit? 

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7 minutes ago, chompy_snake said:

Could you maybe bypass the thermostat or run without it fitted for test purposes before laying out a daft amount on a replacement unit? 

We've ordered a (hopefully) better quality part, if that doesn't work I'll either have to remove it or modify one so it opens earlier or has a partial bypass.

I know the housing the pin pushes against can break but ours is OK, really can't think what else it can be, as the parts of the system before the 'stat (heater, return pipe to header tank) seem to function correctly - but the top and bottom hoses aren't flowing any coolant it seems.

Of course today my Passat has had a lock disaster, never rains but it pours...

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That sounds like a possible blocked radiator with you saying not really anything flowing on the top and bottom hoses. 

If you shop around on ebay they can be had new for just under £40 or as usual I have a passable free one if I could get it to you .... would be tempted to remove radiator and flush it well first off though.

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When I say not flowing I'm going by the temp of the rad hoses - bottom is just warm close to the engine, top is stone cold at the thermostat housing - leading me to think the stat isn't opening. Removing the stat will confirm that I suppose, coolant is perfectly clean with no sign of sludge anywhere that I've seen. Reservoir, inside the stat housing and water pump housing are all clean.

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  • 2 weeks later...

Yet another thermostat fitted (Febi/Bilstein). Still misbehaving. It's as if the coolant isn't circulating past the 'stat, may try a new cover as the 'stat bears on it to open. 

Could still be a blocked rad but the cooling system is so clean I find that hard to believe 

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Thought I'd have a break from the heating system and do the exhaust.

Old box fell off in my hands so it was just a matter of hammer, old screwdriver and a tickle from the grinder to remove the pipe.


Then a couple of return trips to the local motor spares shop to get a clamp that actually fitted (think the one I ended up with is a smidge too large) and job jobbed. Doesn't sound as good but will help stay under the radar when plod are about


Back to the cooling woes - it hasn't been started for 48 hours, yet this is what happens when you turn the ignition on


Now it's not too cold outside, but it certainly isn't 70c. Better quality temp sender ordered...

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Is there an electrical connector near the thermostat? Any / or is the thermostat housing a sort plastic octopus type thing with many hoses?

and, is the rad fan on a lot?

I had a problem with a 1.6 octy with a very similar looking thermostat and various aftermarket bits just upset the car. Replacing the thermostat on its own didn't work and needed the entirely assembly plus thermo sensor before it was happy again.

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3 hours ago, tobyd said:

is the thermostat housing a sort plastic octopus type thing with many hoses?

Yes - currently no stat at all though. Got a stack of them to chose from now!

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  • bunglebus changed the title to Lemon Lupo - cool as a cucumber

Better quality temp sensor arrived (Febi/Bilstein).

Chucked it on, now showing no reading when cold


a run up the bypass and to Halfords for fresh coolant saw it doing what I'd expect with no thermostat fitted


fitted the Febi thermostat, changed the coolant as I'd lost plenty taking it apart 74 times, now runs up to 90 nicely and stays there, fan kicks in etc. Win


bloody cheap shite sensor has had me chasing my tail for weeks!

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  • bunglebus changed the title to Lemon Lupo - smokin'

Lupo has been doing general car stuff, mostly local runs with miss BB behind the wheel prior to her upcoming driving test. Her instructor had gone AWOL but messaged out of the blue the other day, knowing the test is imminent, so she had a proper lesson today but in her own car. 

Thought we'd pop out for an hour this afternoon and follow some of the test routes, got her to do some of the show me/tell me stuff at the same time. Wash the windscreen - all good. Wash the rear screen - wisps of smoke emitting from the steering column. SHIT.

To be fair she handled it well considering we were on a national speed limit road, hazards on, pulled over and switched off in seconds.

We had her grandkids in the car so I wanted to get somewhere safer, so I swapped with her and cautiously drove to a turning. Everything seemed to be working but we didn't touch the wipers again and I drove it home.

Took the column shroud off and I can't find any sign of anything amiss, tested all the washers and wipers and they're working correctly with no smoke. Only thing I could see was a bit of grease around some of the contacts and connectors.

I need to put a fire extinguisher in the car, I've carried one in all mine for years.

Anyone got any suggestions what might have happened? 

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I had exactly that on a mk2 and a mk3 cavalier. But on the ignition switch. It is electrical grease that's got too hot because the contact is not fully made and therefore there's too much current going through half a contact. 

Probably maybe I think in my opinion. No warranty given or implied. 

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