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Discussion Starter · #1 ·
As title states I was having trouble with the car not warming up to optimum,Temp gauge barely getting to 50 and warm air from heater.
So had thermostat replaced car temp now gets up to just over 50-60° while I'm driving. If I stop and let the car idle for 5-10 minutes temperature reaches 90 and stays there until I'm moving again, then slowly drops back down. Heater temp goes up with temp gauge.
Just wondered if anyone has any ideas as what could cause this.
Just in case anyone asks car is a 2007 2.0l Fsi.
Thanks
 

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I would always rely on sensor readings given by diagnostics which are more acurate. What you see on the cockpit gauge isn't always the same sensor used for the engine. If you hadn't had the thermostat changed I would have gone there first because all your symptoms describe a faulty thermostat.

There are some clever systems about now using electronic sensors and solenoid valves to divert coolant flow, but AFIK your EOS design is conventional. The Thermostat housing has 3 ports. Two large ports are used to move coolant from the engine into the radiator. The smaller third port is called 'Bypass' and allows a smaller flow of coolant to circulate around the engine and heater but not through the radiator. When the coolant is cold, the main flow to the radiator is cut off by the thermostat which is closed. As the engine and coolant heat up, the thermostat opens slowly and coolant is diverted to the main flow into the radiator. When a faulty thermostat is stuck open or part open, the engine (and heater) heat up very slowly. Worst case if the thermostat is stuck fully open the radiator will over cool. When you run the engine from cold on idle, the temperature should move up slowly and stay put at around 90C. If you continue running on idle the radiator fans should eventually cut in.

The first and most serious problem that can arise is an airlock in the coolant system. This usually causes the engine to over heat and the temperature gauge could be swinging about. But since the gauge isn't always measuring engine temperature you can't always tell. It's bad news because a cold heater doesn't mean the coolant water is cold, it could mean no water circulating through the engine and strangely, engine temperature sensors can react to steam and give a seemingly normal reading. Old hands always know when a car is about to boil over and stop as soon as the heater starts running cold! If work was done in a V.W shop to drain and refill the cooling system as in your case, it should have been vacuum filled to prevent air locks. Others may have just poured in fresh coolant thinking the system was full but left an air lock. Coolant reservoir pressure caps can leak but even idling the car without it should still give the correct final temperature. The level of coolant showing in the reservoir can be misleading if there's a pressure cap leak because coolant is no longer moving into and out of the reservoir from the radiator as the engine warms up.

If there are no air locks you have to confirm your new (but could be faulty?) thermostat is working correctly and you can do this on idle but keep your fingers away from the fans, moving belts and pulleys!!! Turn off the cabin heater. Locate the thermostat housing and the smaller bypass hose so you can either feel it or attach a thermometer probe. In the same location you should also be able to feel the much larger flow hoses going to the pump/radiator. Start the engine from cold. The radiator fans should be off, if they are on that's your first problem. The large main hoses and the top of the radiator should feel absolutely cold whilst the bypass hose and top of the engine should start getting warm. I would expect this to carry on up to about 80 deg.C. with the radiator fans still off. By this time those hoses should be very hot and remain so. From about 80 deg.C upwards when the thermostat is starting to open, the large hoses and the top of the radiator should start to get warm. The temperature should hold steady at around 90 degC, whilst the radiator from the top down is all getting to an even temperature. The temperature will now have risen above the 90C you see on the small gauge but you only see the real temp with diagnostics. At some point around 102-104 (?) the fans should have cut in and should cut out when the temperature has dropped to about 90C.

The most common fault complaint is the heater takes too long to warm up in cold weather. There are some engine tuning reasons, but the most common problem is a thermostat that won't close and stays partly open, it opens then sticks in one position or it has a very slow reaction time. Thermostats are easily tested in a saucepan of hot water using a thermometer.

If you just paid for parts and work I'd take your car back and ask them to check the thermostat they put in is working correctly as I have described. If they start talking about suspect electric solenoid valves, then the cooling system for your engine is of the more sophistocated design. I think your engine is too old to have the electric auxiliary pump they now fit.
 

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Discussion Starter · #3 ·
Thanks for replying and explaining Voxmagna, when I say heater is warm, I mean it basically matches the temp gauge so at 50 is warm ( I'm always hot so don't really worry me, and I use heated seat for my back) I left the car idling in the drive this morning after a 10 mile drive home, temp showing when I pulled into drive 60°ish , after leaving car running 5 -10 minutes temp had crept up to 90° and the heater was blowing Hot air. I then took car on a quick run around the block and the temp gauge stayed stable at 90°.
As a quick question does the expansion tank lid have a rubber gasket. As mine doesn't, so want sure if it was losing pressure when under load. Otherwise I'm stumped (lol) more worried that there may be an underlying problem that may cause trouble when the real cold weather hits (it's only dropped to 1° so far). So do you think I should run it back to where I got it done ( friends garage so didn't cost a fortune) .
Thanks 👍
 

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A car combustion engine even on idle produces many kilowatts of waste heat. The whole point of the engine thermostat is to keep the temperature of the coolant running through the engine constant whilst removing excess heat. From a cold start the engine temperature should rise without fluctuating and whether you drive hard and fast or idle the car after a drive, the temperature should stay at the same value +- 3 or 4 degrees, Except when the car and engine is stopped. There's always he possibility of a water pump fault, although cavitation from trapped air is similar behaviour. If the water pump is faulty and lost efficiency it may not pump so much coolant around at low engine speeds or hold the temperature down once it starts rising, but over heating doesn't seem to be your problem. A faulty pump seas or corrosion usually causes the temperuture to rise more quickly at low rpm idle, not hold it down.

MY07 EOS needs about 3 miles from a cold start at about 12 deg.C ambient left overnight, to reach the normal 90 C gauge position and doesn't move once there. You can look up the EOS thermostat temperature which I think is around 86 deg.C. My heater starts putting out some warm air even when the gauge is half way. In Summer, if the temperature doesn't hold and rises, the radiator could be blocked. If your car isn't doing this something is wrong. You haven't confirmed if the fans are coming on or not? Fans are controlled by the engine computer and the more accurate engine temperature sensor.

The coolant reservoir NOT THE WASHER TANK should have a pressure cap seal and the system has a working pressure of around 14 psi when hot. They are cheap enough so why not replace it and if you still have problems take the car back for further investigation, preferably using diagnostics to check temperature sensor outputs and rate of rise from a cold start?

By now you are probably overloaded with info, but I've tried to cover all the angles. The one thing missing that can cause unusual coolant temperature behaviour is a small cylinder head gasket leak. If the system is running vented because the pressure cap seal has been broken or removed, that could have been done to hide a head gasket problem?

You say you can put up with a cold heater problem, but if your engine coolant isn't at the correct temperature, the engine performance and fuelling won't be correctly managed.
 

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Discussion Starter · #5 ·
Thank you, it's not too much info, would a small cylinder head gasket leak show as losing water, as water level hasn't changed and it's still a clear bright red, also the other way around oil is just off light brown and not creamy. The coolant reservoir tank has a screw on cap but no seal just the black center pressure release valve. I'll give the garage a call and see if they can take it back in and check. It's just a case of when as they are busy in the mean time I'll order a new cap and see if that helps.
I wasn't saying I could put up with a cold heater, I was saying I can put up with a slow heater for now, car does get nice and warm inside, I have warm air blowing after about 500 yards. It only gets really hot though if I leave car idling. It's a bit awkward to check fans as I work nights and the car doesn't get used during the day,
I'm hoping it is something silly like the coolant tank lid . Car was running Fine throughout the summer and only send to stay playing up after I checked the coolant level due to a low coolant warning. ( It was dark and I wonder if the seal fell off when I opened the tank. )
Thank you for taking the time and effort to help me Voxmagna .
 

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Why did you get a low coolant warning? That level sensor is quite a way down from memory? I have never topped up my coolant level in 5 years, but i do need to change it now. If coolant has been lost it's either due to a leak or engine over heating and pushing it out through the pressure cap?

My EOS is the Tdi, but I'm sure when I last loosened the blue cap it was quite hard to turn due to the seal. It eventually loosened with a squeeky feel I would expect from a rubber sealing ring or gasket under the cap?

Cyl. head gasket is the last thing to consider after looking at everything else -soooo much work. You don't see a water leak necessarily because a small head gasket leak is just going to add pressure to the system and the only way it gets out is via the pressure cap, which is why some perps selling a car knowing this will remove any sealing on the reservoir cap. If you have had the car a long time and it's been o.k in the past, this trick won't have been done, but still check the cap seal and system can hold pressure.

The level of coolant in the reservoir should change by small amounts when the system is working correctly. At cold startup the level should be at its lowest low normal mark. When the engine is left to idle and coolant expands heating up, coolant should come back from the radiator and the level will rise 'a little'. In fact coolant in the bottle should start to feel a little warm. After a drive at normal temperatures when the engine is left to cool down, the coolant (BUT NOT AIR) is sucked back into the radiator and the level returns to the low normal level. If coolant levels in the reservoir are not cycling, it suggest that either there is insufficient in the system and there is air space at the top of the radiator, because it was not filled with a vacuum tool, or the system isn't sealed and able to produce pressure and then suck coolant back. Some but not all radiators have a filler plug on one corner. When the engine is very cold before first start, if you undo this, coolant should be at the very top of the rad. and leak out. There should be no air space at the top of the radiator or in the top hose. Without the rad. plug you can do somehing similar loosening the top hose. You are describing two scenarios. One is the engine isn't at the correct temperature, getting there fast enough or holding and that has a consequence for the heater performance. The second scenario is the engine is nearly doing what it should and a problem exists in the heater loop. Air locks in the heater loop are very common. I vaguely remember some V.W engine Climate control systems (not sure about EOS) have an electronic solenoid valve in the heater flow line coupled to the matrix just as the flow (return?) hose goes into the firewall? I think the idea is to stop flow to the heater matrix when it's turned off or control heat flow in a better way than using motorised flaps.

Start with the easy things:

1. Check the pressure cap and seal.
2. Use a coolant vacuum tool to ensure all air is purged from the system and the reservoir coolant level is correct (Actually a V.W Workshop procedure!)
3. Cooling systems can be pressure tested: At a pressure of around 10psi or just below the cap rating, the system is pressurised from an air line and the pressure monitored over 5-10 minutes. If the pressure drops, there's a leak somewhere including the head gasket, but head gasket leaks can be very small and don't always show until the engine gets hot and parts expand.

Whilst the coolant system is being monitored for pressure the engine is run. Pressure should increase slowly as the engine warms up. When the normal 90C temperature is reached, the system pressure should be below the pressure rating of the cap. If pressure carries on rising close to or above the pressure cap rating, the most likely problem is a head gasket leak, particularly if coolant system pressure changes in response to throttle rpm.
 

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Discussion Starter · #7 ·
Low coolant alarm, was a false alarm. Reading through this forum I'm guessing it was just a case of dirt on the sensor bars. Car has never used any water and I've not had to top it up ( had the car for a year now but only been using it for the last 9 months). Also car was VW serviced just before I got it
I popped to Europarts it's just down the road, but they don't have the cap in stock at the moment. So I'll try VW dealer at the weekend. After driving around this late afternoon car got up to temp and just floated up and down 80-90° quite happily. But that was driving in stop start traffic. My 10 mile drive to work is at 21:00 when there's no traffic so the car never really sits at any time with the engine running. I will also try and check the rad top pipe, to rule out an air bubble. Owing to sleeping while it's light, it's hard to sort out problem until the weekend.
Think I owe you a large drink for all this.
It's people like you that make these forums such a great help.
Hopefully I'll be able to post some sort of answer as to being fixed after the weekend. If not I'll have to give the garage a shout and book it back in.
 

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After driving around this late afternoon car got up to temp and just floated up and down 80-90° quite happily.
MY07 Tdi doesn't do that. It rises up from cold and stays put not moving at all, even during Summer. If you can estimate 10 degC on that small display it's probably a lot more?

Before you rush off to order a cap, why not take yours off, turn it upside down and look for a rubber seal? You should have all the info now to get a solution.
 

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MY07 Tdi doesn't do that. It rises up from cold and stays put not moving at all, even during Summer. If you can estimate 10 degC on that small display it's probably a lot more?
As I understand it, the temperature gauge uses some kind of computer-controlled magic, because people pay too much attention to the temperature gauge. So it's programmed to stay at bang on 90 when it's up to temperature as long as nothing unusual is happening - which, obviously, means that it will only come down if something unusual is happening (for example, it's -15 outside and you have the heater on full blast). If it's not significantly below zero outside, any downward deviation from 90 is a sign that something is not right somewhere under the bonnet.
 

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Discussion Starter · #10 ·
Cap has no seal , so will go and get a new one possibly Saturday. If that doesn't work, then will take it back to garage and get them to check the temp sensor.
Aku-aku outside temp is 3° so it's heading towards cold, so miles away from -15 .
After that it will probably be a VW dealer diagnostic.
Will try and keep you updated as to what's going on
 

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As I understand it, the temperature gauge uses some kind of computer-controlled magic, because people pay too much attention to the temperature gauge.
It's the same with fuel gauges. The cockpit displays are non- linear because they are designed to let you know about important changes. They will suppress the low end e.g from zero up to the bottom of a 'window' and expand the scale above normal. You aren't interested in coolant temperatures below about 60C but you are interested when it moves above 100C. I'm not so interested if my fuel level is over half a tank, but I am if it's below 1/4 (where the scale is electronically expanded) and I'm driving on air to the gas station!

Diagnostics gives the real 'linear' output of temperature sensors and you have to be careful because dash gauges sometime use a suppressed or coarse range sensor near the water pump. The important sensor for the ECU can use a similar but wider range more precise sensor in the cylinder head. That one tells the real truth about engine temperature. Which is why I mention the boil dry scenario caused by airlock or loss of coolant. The cylinder head at the highest point and more prone to air locks loses coolant first, steam is produced making things worse because its pressure pushes more coolant out of the engine into the reservoir until it sprays out past a pressure cap. The dash gauge doesn't immediately fly off the scale. The heater going cold and in the cylinder head cooling loop can be the early warning indicator of problems.
 

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Discussion Starter · #12 ·
Will keep an eye on heater, Touch wood this morning driving home 3° outside heater was warm in under a mile and lovely and hot in just over 3 miles. But temp gauge was sitting at just over 50°, think the sensor may be going home.
When ever I state heater is warm, it's because most of the time I only have the heater temp set to 18°.(I'm always hot, wide says in going through the menopause because I'm over 50, lol the cheeky moo )Today I thought I would drive home with it whacked to the end stop, and it warms up ok .
 

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You cannot jump to conclusions. The EOS like most modern cars is very complex and temperatures from a diagnostics tool are the only thing you can rely on. The temperature you feel from the heater with Climate control doesn't always correlate to what is happening in the engine cooling system. I would rather know the engine temperatures are behaving correctly because if not they can cause poor performance or stop the car. Whereas I can tolerate not feeling so warm which is subjective, even between vehicles. Heater matrixes can get blocked or the flap controls don't work as they should. If I was replacing a water pump I would reverse flush clean a cooling system at the same time.
 

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Discussion Starter · #14 ·
I've ordered a new cap and pick it up Saturday morning, if that doesn't make a difference I'll run it back to the garage on Monday morning and get them to check it out.
And yes I fully agree modern cars are way to complex, prefer the older cars, without So many sensors.
 

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modern cars are way to complex, prefer the older cars, without So many sensors.
But they can't meet emissions regulations, lower gas consumption and Government rules without them. Hydrogen and EVs are the future. Ammonia has some potential but power to weight isn't good. Personally I'd like a totally water based combustion engine. :)
 

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I have planned for our next cars to be electric and my partner's Eos will be kept as our "classic" car for special occasions until diesel fuel becomes a past memory.

I have recently ordered a solar electricity system with a Tesla Powerwall 2 Li-ion battery storage system which will allow us to go "off-grid" plus recover the cost of the installation through power transfer to the national grid as well as charging our electric vehicles. We are installing recently-released LG Neo solar panels which have a 25 year warranty and the calculated pay back period from sales of surplus power to the grid will be in the range of 6 to 8 years depending on any changes to the feed-in payment. Big bonus for us will be the fact that we can run our air conditioning system 24 hours a day summer and winter free of power charges and the same will apply to our hot water service as well. The system is also large enough to run our electric oven and hotplates concurrently with everything else and still have capacity to export power to the grid. The cost is around AUD30,000 including installation for a system generating 34kw or more depending on cloud cover.
 

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Wow that's a pretty big array for 34kW! We have similar feed-in incentives here. When they first started in UK the Gov incentives were attractive to kickstart solar, but less so now they have reduced them. Your panels are LG brand, but won't they come from China (may be assembled in Japan) and isn't Aus having a barney with them at the mo. Seems strange Aus digs out lots of black stuff and sells it to them to generate greenhouse gases.

UK gov boffins want all our domestic gas boilers out within 10 years, but we have millions of traditionally built houses without modern insulation. They think we can keep warm with heat pumps or solar panels and have the land area in our gardens to install them. Perhaps emigrating to Aus. isn't such a bad idea? Some nuke power stations were in the pipeline but they bottled out of one being started by the Chinese. Now they think mini nukes made by Rolls Royce on multiple sites might work. Less fallout if one goes bang I suppose. Curiously with Brexit next year, they've just finished 2 undersea cables so we can buy electric from France.
 

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Hi Vox, the panels are made in South Korea and are top quality being hail-resistant - important for our location being prone to summer storms coming off the mountain ranges behind the Manning River Valley. The 25 year warranty includes hail damage.

There are cheaper panels available for those who only buy on price however you get a "double whammy" - lower output and prone to hail damage. The most expensive item is the Tesla PowerWall 2 .system which is close to half the cost of the installation. This is essential to allow best possible fast charging of an EV. I am not in a hurry to buy at the moment as our Mazda CX5 diesel SUV .was purchased with the intention of a 2004 changeover or earlier if we get to 200,000 km. It is a great highway car, very comfortable {important for me as I am187cm [6ft 2inches] tall}, cruises up hill and down dale effortlessly without losing speed, accelerates promptly when needed for overtaking and averages 6litre/100km fuel economy. Of course, the Mazda has to be parked in the street as the Eos gets the 2 places in the garage so the doors can open fully for me to get in :eek:.

https://www.canstarblue.com.au/electricity/brands/tesla-powerwall/
 

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Discussion Starter · #19 ·
Ok so a quick update.
And it's good news, took the car back to garage Monday night for then to check Tuesday, they took the pipes of drained the car and refilled, test drove it and still the same thing. So Wednesday they took the T stat out replaced that with another new one and refilled again. Success the gauge now warms up to the middle within a couple of miles and hot air blowing within a few hundred yards.
It was all down to a faulty new stat.
Thank you guys for helping diagnose the problem and messaging with what it could possibly have been.
Wishing you all a merry Christmas. (y)
 
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