Engine thermostat on a Polo 1.4

I'm not overly familiar with the engine, but it shouldn't be too much hassle. Thing is I'm not convinced it's the thermostat that's causing the problem.

They fail in the shut position, causing overheating, not a lack of it. Is your friend sure that someone hasn't removed the thermostat?

Steve

They can do that - but equally they fail when the spring gets old & weak & so they open too quickly & stay open too long. That leads to low running temps as has been described.

I've replaced T'stats in all three of my cars (one is a VW & another an Audi) for exactly this reason in the last year. All are now running at correct temperatures.

I.

I hope I'm never in the same aircraft as you. Not with your luck.

Steve

The Skoda failed closed, but I'm happy for it to fail open. The guy who owns the Polo is a bit of an oddball. He just happily reskimmed the head on his bike himself but doesn't seem able to scale problem up a litre or so or think in the same terms. He's similar with his work. He misses out on basic stuff that I can do asleep but then writes Perl scripts that give us the kind of control of the network that we'd have to fork out hundreds for.

Typically he's mentioned the problem to me after getting through the worst of the winter.

I considered the possibilities of water pump, leaks, etc. Revving it in the carpark at lunchtime got some heat in eventually and slowly brought the needle up on the temperature gauge. The fan kicked in about when you'd expect and it was blowing hot by then.

The return water hose is pretty obvious and I can't think of anything else that would cause it to behave that way. It heated up pretty fast where a comparitive test on my pug held the return hose pretty cold for a lot longer. (I had to demonstrate to prove my point).

Now I just need to persuade him to buy the flipping part and I'll take my socket set to work and fit the replacement.

Warwick

I've replaced two stats this year in a megane 1.6 that both failed open within months of each other.

LOL, its a funny thing - trouble comes in threes I guess.

Usual story, I find the one on my car broke & the Mrs turns around & says oh my car never gets up to 90 on the temp gauge.

Q. "How long's this been going on?" A "Oh, a while......."

No wonder the bloody thing was drinking fuel!

The third one, well that's another story - proper car without a rigged temperatur gage (did you know the gauges on most modern cars are rigged to read 90 C /190 F within quite a wide range? Apparently Joe Public gets freaked if he sees his temp gauge creep up by 5 degrees & so the manufacturers just rigged the gauges to avoid the aggro of explaining that there wasn't a problem!).

Anyway, proper car with no rigged T gauge - doesn't get driven much, eventually decided that the Stat was weak - and indeed it was.

I.

FWIW the other problem with this engine is that the impeller on the water pump fails, leaving only thermosyphon to cool the engine. Naturally, none of this warm water goes through the heater :-(

WTF is thermosyphon? You mean convection?

Amongst other things, it is the way water-cooled internal combustion engines were cooled before water pumps were invented.

No, she means thermosyphon.

HTH

Chris

Thermosyphon IS natural convection - heated fluid rising and being replaced by colder fluid, acting as a pump, its just a term thats little used these days apart from in solar energy circles.

So if you know what it is, why did you ask the OP "WTF is thermosyphon"?

The term is only little-used these days in the context of vehicle cooling systems; the way the OP used it was perfectly correct, and easily understood.

Chris

Thanks for the response re thermosyphon; the Noddy Bike I used to pass my test was water-cooled via this phenomenon - it said so in the handbook LOL.

What surprised me about the 1.4 Polo engine is that there's enough thermosyphon action to keep the engine functioning; unfortunately none goes through the heater :-(

Because i wondered what it was, and posed (thinking out loud i suppose) that she meant convection. Then i checked.

i.e. these forums

I was merely asking a question, not accusing anyone of being wrong, get off your soap box.

Perhaps to avoid making yourself look both rude and stupid, you should consider doing things the other way round in future?

Yes, amongst others. In other words, places where cars are discussed...

"WTF is thermosyphon? You mean convection?" does not seem to me to be merely asking a question.

I don't need a soapbox in order to express my views. I have Usenet. (Or "these forums" if you prefer).

Chris

It could only be construed as rude or stupid if you are looking for an argument. I fail so see the problem with asking a simple question, when i got a smart-arsed one-line response from you instead of a constructive answer I went looking for a better source of information, which wasnt hard to find - admittedly I was stupid to assume you could give a contsructive reply.

Yes, so its little used on here (and other places where cars are discussed), therefore its not likely that one might have come across it before. Hence needing to clarify.

Thats just the way you read into it, im sorry you took it the wrong way. I could be all flowery and nice and word it so it could never offend anyone, but as it was an off-the-cuff question and hardly of great importance I just replied as I would in a jovial conversation. I dont treat Usenet as formal document in which I must prepare everything i write, i treat it as it is - an open public place to discuss informally.

I was using 'forum' in the wider sense of the word. And no you dont need a soapbox, you're loud enough right there :-)

Right, ive wasted enough time arguing about a simple question, I have work to do.

The message from "Coyoteboy" contains these words:

That'd be nice.

For what it's worth, in the context of engines I've always called it a thermosyphon and have rarely if ever heard it called convection except when it's being explicitly explained rather than just referred to.

As would a lottery win.

Maybe thats why i have never heard of it referred to as that, I'm a mechanical design eng and we tend to use the plain explanatory terms as a matter of habit. I'll know from now on though ;-)

Perhaps to avoid making yourself look both rude and stupid, you should consider adding attribution lines in future?