NefMoto

Hi All,
So Thermostat failures are so common that people remove them soon as they buy a car. I bought my car without a thermostat and then bought one. Recently pipes started bursting, and I'd replace a pipe, only for another to burst after a few minutes of driving. Removed the thermostat, and problem went away, so I assumed it's stuck open.

So question is, what maps do I need to modify to lower engine operating temperature. Not by much, but just such that on cold days (18*C), my engine still runs as though it's at 90*. Would like to lower it to 80*.

Kind regards,

What???

You do understand that the thermostat is a physical object?  You can't modify it with maps.

I just smite and didn't bother to explain with what I think.

Not on all ecu's. :)

Wow, just..... wow.
I have never heard of "removing thermostat" as a common thing ???
It's probably the cheapest easiest fix to replace a failed thermostat.
If your coolant pipes burst when the thermostat is in the system, I would say that the coolant pipes are waaay overdue for a change.
My immediate thought wouldn't be "I'll remove the thermostat because that must be the cause of my pipes bursting"
Do you know the reason why the cooling system is under pressure and the function of the thermostat?

I know that not all are equal in mechanic skills.
But this train of thought just boggles my mind.

May I ask what your reasoning is in this decision and where you got this idea from?

This isn't what I meant at all.
- I mean the thermostat is supposed to keep the engine running at around 90*C.
- The engine expect to be running around that, before that temperature, some things are disabled -- like misfire detection.
- I want to make sure the engine is running as though it's at optimum temperature, from 80*C - 95*C

The reasoning is simple:
- In warmer countries, the thermostat isn't that useful. It's a little bit useful, but not extremely so
- Therefore one weighs the benefits of having it (and have it fail, overheating etc), Vs just removing it, and taking a bit longer to reach operating temperature

A thermostat cost like $10 and takes 20 minutes (max) to change.
The function of the thermostat wil always be useful.
You could buy a thermostat with a lower opening temperature,
Or alternatively drill a couple of holes in the thermostat casing?

What are your commonly hottest and coldest temperatures where you live?

Coldest: 18*C, Warmest 30*C
A Thermostat costs Around $50 where I live, and changing it took a very long time, the bolts we worn out. That's not accounting for the damage it causes by getting stuck closed.

That reasoning is about the same as not running a fuel filter because it can get clogged...

To answer your question, there are many maps that incorporate coolant temp. But at 80* the ecu should function the same as at 90* for as far I have seen in my files...

That's not a hotter climate (max) than where I live, and I have almost never experienced the problems that you describe. And the engineers have tested the cars in more extreme climates.

Always replace old bolts, it makes everything easier on yourself the next time :)

$50? Where do you live?

Thermostats rarely fail because of the simple way they're made. So if it fails it's either shit quality parts or really really old. Don't get me wrong they do fail, and I have experienced a couple of them myself, but they're far apart :)

Do you run just straight water in your cooling system of antifreeze mix? :)

Oh, thanks. I run without it for a while an observe. I'll update thread

- I'm not saying the climate ruined the thermostat. Just justifying that I probably don't need one.
- Bought the one that failed off ECS less than 6 months ago
- Unfortunately been runing straight water. :-X :-X (where is the running emoji when you need one?)
- I live in Kampala, Uganda

I still just can't understand why your climate would justify removing the thermostat entirely. It has a purpose regardless of climate
Running straight water could very likely cause corrosion in the cooling system which could seize the thermostat.
One of the benefits of antifreeze is that it also inhibits corrosion :)
Also water with high content of calcium could possibly cause some problems.

Have you checked for  pressurising of the coolant system? I suspect you have an underlying problem

Coolant also lubricates water pump bearing too

How do you know it failed?

Never had an issue.  Genuine VW, no problems.  I ran water for 2 years too. 

Interesting question -- I took the mechanic's word for it. Now I've just checked by boiling it in water, and it actually opens. So it's still fine. WTF.

Please give me more information on this. I believe I have an underlying problem, which isn't the thermostat.

Use distilled water and a proper coolant :P

Pressure blows rubber hoses not temperature, unless your hoses are about 25/30+ years old

I suspect you have pressurisation in your coolant system be it from slight headgasket failure or other reasons

Would knock cause head gasket failure?

100 dollars says you've never seen a 2.7TT thermostat and don't have a clue where it lives :D

And you would win ;)
But there was never a mention of it being a 2.7TT
Or any mention at all what car it was, and that is my error for not asking in the first place :)
But since he has tried it himself, I'm assuming it's more likely a 1.8 20vT  :P

Edit: just researched 2.7TT thermostat, and that is just a ridiculous amount of work for such a "simple" thing :P

Severe knock/detonation could cause that, yes :)

At least the 2.7t afterrun thermostat is "easy" to get to :)

I have some knock, but I wouldn't call it severe. But again, I don't know what severe is. Like 5 knock events in a 2k-6k pull severe?

Even slight knock events over prolonged periods can damage a headgasket

Easy way to diagnose a faulty head gasket is to run the engine with coolant cap removed. If you see bubbles, for sure the hg is defective. If there is no bubbles, no guarantees  ;D I had an 8v that would pressurize the system, it held for 2 months and then it just gave out in one big cloud of steam and flooded cylinders...

I heard bubbles just as I parked now. I heard a bubbling sound in the cooling system. Will check when I get home.

Mine would bubble but I had a leak.

You need to sniff the coolant bottle when engine is cold through to up to running temperature for hydrocarbons either emissions machine or a use a block tester kit but these aren't always accurate

Can I use my nose?  ;D

Nope.

If you have access to a leakdown tester, use that and remove the coolant cap. Set TDC on any cylinder and if you get bubbles at the coolant reservoir. Then you've got a blown headgasket. This is the most accurate way to sort out a bad headgasket. Along with a compression test as well.

Question, have you seen any consumption of coolant from the bottle?

Also, back in the day I remember many mechanics/friends would remove thermostats due to the fact they sucked ass and would fail regularly.  So the common fix while in a bind was to remove the thermostat to make it back home.

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I don't have access to a leakdown tester, but replaced water with coolant, and ran with the aux fan on all the time (Unplugged AC compressor, removed its belt, and turned on AC).

Still at some point it would feel like the coolant is boiling -- the temp gauge would be at 90*C, and the Oil Pressure light comes on.

90c is within operating temperature?
Oil pressure light? Sounds like you got more problem incoming :)

Oil temp through the roof and so thin pressure has dropped?  That motor sounds toast.  Pump working?

- What do you mean motor sounds toast? What's specifically is likely to be toasted?
- Water Pump?

He's saying you've got a pressure light coming on, you may have a bad oil pump, but in reality you should be checking the oil pressure sensor. I just recently had one fail. Plus this would be a great opportunity to check your oil pressure by hooking up at the same port using a pressure gauge. That said, there was no mention of oil temps. Unless I missed it.  Coolant temp at 90C is ok, though it seems it's over cooling being you've got the fan on all the time. My S4 sits at factory temp of 203F.



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I think the oil pressure light comes on because the oil has heated up. I think the sensor is fine. The coolant just boils and evaporates through the cap

I've had problems with head gasket, thermostatic valve and water pump.
Each one of a symptom before having overheated.
  Head gasket you will have the engine starting cold failed cylinder, or drive the car for 3km with cold engine and an accelerated in order to come turbo pressure, stop the car even with cold engine and check that the hoses are under pressure, Yes, you have a burnt gasket.
 Water pump or coolant, turn on the car and then turn on the air heater at maximum temperature, if you do not notice heating inside you have a fired pump, the warm air of the cabin and the place where you first notice the heating. You can check the two radiator inlet hoses of the cabin heater. The factory pumps break the pas when the mileage is high and you drive with high rpms still with cold engine.
 Thermostatic valve you will have the cabin heater normally operated, but when you have the radiator fan driven by the temperatira of the engine will have cold air coming out of it, one radiator hose will be hot and the other cold.
I speak here of a motor 1.8 20v auq.