MK5 Golf GTI
All Things Mk5 => Mk5 General Area => Topic started by: fsgti on December 04, 2022, 05:12:10 pm
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May be an obvious question but isn't clear cut to me.
I'm pretty certain I have a thermostat issue where it's stuck open and hence it takes ages for coolant temp to reach 90 degrees. Prior to this it would sometimes drop from 90 to around 80-85 and then rise back up.
Anyway cutting to the question:
Even though the coolant may not be up to temp, the engine oil surely should reach normal operating temp after 5-10 mins of driving regardless of the coolant temperature, right?
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If you're asking if you can get away with not fixing the answer is no really. Not that you can't drive it like it is but you should do it within a reasonable time. Not sure what the engine temp would be unless you ran some logs, it would be at the very least warm but maybe not "up to temp".
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If you're asking if you can get away with not fixing the answer is no really. Not that you can't drive it like it is but you should do it within a reasonable time. Not sure what the engine temp would be unless you ran some logs, it would be at the very least warm but maybe not "up to temp".
What mechanical damage could be done to the engine from 'overcooling'? I'd understand if it was stuck open as that leads to overheating and thus catastrophic damage. I guess I should probably just wait much longer than usual before going well over 2000 rpm.
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In my experience you will get worse economy with a stuck open thermostat, so eventually it will pay for itself so just get it sorted.
If the engine isn't at normal operating temp you'll be putting more wear on moving components too
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Yeah you gotta get it fixed really mate. Its a faff if you do it yourself or expensive if you don't but needs to be done at some point soon really. It's like missing an oil change - yes you can still drive it, no its not going to blow up by just missing an oil change interval but you're just potentially decreasing the life of your engine or asking for trouble by neglecting it.
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Mine had a bad thermostat when I first had it - the ECU will assume your engine hasn't warmed up and will be dumping extra fuel in - cold starting & city driving, mine was drinking petrol down to 4/4.5 miles per litre.
Thermostat is only awkward to change because of tight access - BTW, I highly recommend changing the temperature sensor at the same time, you don't want to be going back in there any time soon.
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My experience of replacing an old wonky thermostat is in line with what others are saying above. The car warms up quicker - both temperature gauge and heater system - and delivers better economy. I even got 44mpg on a run to Heathrow to collect my daughter last summer! As it’s a ball-ache of a job, best do together with other work (cambelt / water pump for me) and change that temperature sensor at the same time.
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Mine takes a little while to warm up but is solid once it gets to 90C. It recently occurred to me that I knocked out the pre-cat, the pre-cat will help the engine warm up quicker so I've put mine down to that since the thermostat is relatively new.
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I've noticed from logs that as soon as it says 90 on the needle the temp sensor is actually reading less than 80 and needs a few extra minutes. As a rule of thumb I've started waiting 5 minutes after it hits 90 now to make sure coolant and oil are a good temp before booting hard.
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Yup. 83 is the actual cruising temperature once warmed up. 90 on the dash is just the de-panic number to keep it in the middle for people who like things in the middle.
Similarly, when the temp goes over 90 and just prior to stage 1 fans kicking in (around 105 deg C), it's also sat at 90 degrees :grin:
Bashing out the pre-cat has no bearing on warm up temperatures. The default cat warm up mode (double injector pulses) remains, even when remapped and/or cats bashed out. The engine is none the wiser, which is annoying as tuners could easily turn that off to save some fuel.
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I now have this same sympton. Looked at the Pelican parts how to and it looks like a right faff, alternator off etc, and it's minus a million outside.
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Yup. 83 is the actual cruising temperature once warmed up. 90 on the dash is just the de-panic number to keep it in the middle for people who like things in the middle.
Similarly, when the temp goes over 90 and just prior to stage 1 fans kicking in (around 105 deg C), it's also sat at 90 degrees :grin:
Bashing out the pre-cat has no bearing on warm up temperatures. The default cat warm up mode (double injector pulses) remains, even when remapped and/or cats bashed out. The engine is none the wiser, which is annoying as tuners could easily turn that off to save some fuel.
Stage 1 fans at 105 degrees? Surely not? Mine kick in about about 95, car has never gone over 96. Did the thermostat earlier this year as the old one was starting to show symptoms - slow to warm and never got over 92 degrees.
Dash shows 90 from an actual temp of 75 degrees C, still has another 20 to go... Oil takes even longer to get there