2.0 16v still running too hot...

[Jim 1]

Following on from my old thread:

 

viewtopic.php?f=1&t=68992&p=810530

 

I figured that had got a bit long / full so wanted to start fresh - there was some useful information in there and when I reach a conclusion on this I'll bind the two up into a single useful thread for troubleshooting.

 

I've now replaced in the last year all of the following:

 

* Radiator - genuine VAG

* Radiator fan switch (twice!) - both genuine VAG

* Water pump (VAG)

* Thermostat (GSF......)

* Coolant - genuine G12+ (has been flushed so many times now it is totally clear / pink with no contaminants or debris)

* Expansion tank (genuine VAG)

* Dash coolant temp sender

* ECU temperature sender

 

The car is still getting too hot when in traffic. Recently in roadworks on a busy day, even with the heater on full whack and the windows open to try vent heat out, oil was over 120 centigrade and the coolant temp never dropped below 110 centigrade. It's absolutely fine and sits on the line when driving normally (90 degree coolant, 100-104 centigrade oil) but as soon as you stop, you can literally watch the coolant temp climb quickly. I pulled up at some lights a few days ago and in the few minutes it took for the lights to cycle my water temp went from about 75 centigrade, to about 105 centigrade - I was literally watching the needle moving up the gauge.

 

I don't understand why, with all that stuff changed, the car can't regulate its temperature. The fan is coming without a doubt and I can hear it running when I come back from a drive.

 

So starting to wonder about whether the cooling system is ok and whether the engine itself is just running too hot - i.e. not fuelling correctly or something? At the RR day a while back I recorded 140BHP. Everyone was getting expected figures and I too expected more given that I have the KR cam and i'd stuck in some premium fuel beforehand. I'm debating getting my injectors changed soon as they have to be gummed up and grim on a 187k mile engine, and I think my air filter is passed its best despite being a rechargeable one... anything else that could cause the engine to struggle?

 

Any other suggestions on stuff to check / replace welcome.

[mrbeige 0]

Could conceivably be running lean if your injectors are shot, that would cause a hotter burn, but bit of a long shot I think. Could be getting some detonation, if your timing was out, but you'd have the ECU retarding the timing because of the knock sensors (if they are functioning), but then you wouldn't really get that sat in traffic.

 

What about you're thermostat? Might be worth replacing that with a VW one, or at least checking it opens fully? Can you tell if both top and bottom hoses are the same temp when running as hot as it does?

[Jim 1]

I was debating getting the low temp Thermostat and Fan Switches from Awesome GTI mate but thinking I should sort the core issue out rather than use work arounds.

 

Fairly sure the thermostat is opening up ok - rad pipes get warm at the right sorts of times... :(

[tandino 0]

I think as a starter i would temporarily pull the thermostat out to see if the car can hold a stable temperature in traffic with nothing to impede the flow through the stat housing, if it can then the problem lies in the thermostat or the fact that it is impeding flow enough through the housing to allow the temps to creep upwards.

If removing the stat stabilises the temperatures then the cooling system in theory should be capable of holding the temperature steady which would say the thermostat is not allowing full flow even though it may be working correctly, Pattern part??....

What is puzzling is that your temps are stable when moving which does rather point to your cooling fan not flowing enough air over the rad core???

[Jim 1]

Indeed. This is opening an interesting can of worms also and makes me wonder if there is something in either the waterpump or thermostat and whether either of them are somehow preventing the coolant from flowing round the system properly. I say this for a few reasons... firstly, quite often when I pull up I find that the fan won't immediately come on even if the car seems warm simply because the coolant in the radiator is relatively cool (where the fan switch works from) but the coolant in and around the block is really hot - hence the dash temp sensor reading quite high. That could lend credence to the duff waterpump / thermostat theory.

 

Additionally, ever since having the stat and pump done, i've always had the coolant light flashing on the dash first thing in a morning - it never goes away again until I stop / restart the car once its warmed up. This is despite the fact that the level in the expansion tank is never below max even first thing in a morning. I wonder if there is some kind of weird pressure drop or something when I first start the car causing the level to drop momentarily causing the flashing light to trigger..?

 

I do think the stat is worth a look at first definately.. slightly cheaper and easier to tackle than the water pump :)

[davidwort 0]

It's a wierd one, but a stat change is always worth a go, VW ones are not unknown to come in dodgy batches.

Can you fully describe the engine coolant and oil heating process from cold with the time it takes for the gauges to come up in both driving and idling? - that might give some clues.

Bally has/had a similar problem on his 1.8, I even swapped oil temp sender over to eliminate that. it did improve with a genuine stat change.

When was your oil cooler changed?

do you have the heater bypass valves (recall job) and d you know how many miles they've done, how hot does the hot air int othe car get?

[Bally 0]

It's a wierd one, but a stat change is always worth a go, VW ones are not unknown to come in dodgy batches.

Can you fully describe the engine coolant and oil heating process from cold with the time it takes for the gauges to come up in both driving and idling? - that might give some clues.

Bally has/had a similar problem on his 1.8, I even swapped oil temp sender over to eliminate that. it did improve with a genuine stat change.

When was your oil cooler changed?

do you have the heater bypass valves (recall job) and d you know how many miles they've done, how hot does the hot air int othe car get?

 

Yeap, big thanks for all yr help David..

 

I'd look at changing the stat for a gen one Jim.. even when dave & tested the new one to the patern part, the stat was opening fine... but since doing the stat to VAG one been running alot cooler.. only thing Im finding is the oil temps get high on a very hot day.. water temps seems to be alot cooler though...

[Supercharged 2]

I'd also be thinking about other stuff Jim like a corroded metal pipe causing a partial blockage... my G60 ones weren't too bad at 100k but new ones should still make a difference...

[Jim 1]

Cheers for the replies guys and glad people still have some interest in working this one out!

 

Can you fully describe the engine coolant and oil heating process from cold with the time it takes for the gauges to come up in both driving and idling? - that might give some clues.

 

Well my normal drive to work is getting the car out of the garage then a steady 30, then 40, then 50MPH (different sections of road) and then briefly onto an A road at 60MPH. Takes about 10 minutes to get to the A road and by then oil has normally got to mid low to mid 80's and the coolant gauge is generally sitting reasonably low but does move up from cold fairly quickly - gets to about 75 and tends to sit there if i'm just dawdling along. I do the A road blast and come back off again but then there is fairly steady 50 then 40MPH driving - by now coolant has crept up a little (to below 90) and oil is about where is should be mid 90's. I then come and sit at the traffic lights and watch the coolant creeping up from mid 80's possibly to 100 before I move off again. Oil tends to sit in the right sort of spot unless i'm sitting in an extended queue - if I do then it does start to creep up.

 

By the time I got to work oil was at 102 centigrade, coolant needle on the dash read around 105/110 but strangely the radiator fan wasn't on again. I'm still convinced that cool coolant just isn't circulating round the system some how - the rad fan switch thinks the coolant is cold where it reads from but somehow it's not as cool up in the block, lending credence to a blockage of some sort.

 

Could an air lock cause this?!

[davidwort 0]

your warm up sounds pretty normal, I'd expect oil to peak after about 20 minutes steady 60mph driving from cold and water to rise faster as the shorter circuit with the stat closed means there's less coolant to heat up. In fact the system with the heat exchanger is designed to help bring the oil temp up and then use the extra capacity of the coolant through the radiator to help keep the max oil temp down.

The final part of warming up would be when the stat opens, and on some cars this can slightly reduce the water temp for a while as the cool water in the rad circulates.

I'd suggest you now run it from cold for 10 minutes or so idling, feeling the various hoses for heat build up. The exit from the right of the head to the matrix should be very fast as it's the top of the engine, this would also indicate good flow out through the matrix and back down the water pipe to the pump and heat exchanger.

The bottom radiator hose should stay almost totally cold until the stat opens (which only takes a few secs when the water reaches about 80 degrees), at this point the bottom hose and the mid and bottom half of the rad should warm quickly and after a few more minutes the first stage fan should come on once the bottom of the rad (around the fan switch) makes 85 degrees or so.

If it's a breezy day or relatively cool it may take quite a while for the heat to build and the fan to run especially as you have a newish VW rad, they cool a fair bit even with little airflow, particularly with little heat to be dissipated at idle.

It's not impossible that you have some kind of partial blockage in the head and it would also be intersting to get an oil pressure check done as your engine is pretty high mileage ,I'm not sure, but I'd imagine a partially restricted oil pcikup pipe or warn oil pump would in some way contribute to warmer running if oil flow and pressure is a bit down? - perhaps someone else can comment on this?

[mattnorgrove 0]

Jim, could it be temp sensor/sender related?

 

Just a thought, as you don't mention having changed them, could it be that the engine is perfectly happy, but reporting incorrectly to the guages?

[zoonders 0]

My 1.8 16v does pretty much the same. I think I am getting a bit paranoid everytime I get held up in town as it does get bloody hot but always gets me there. Mine has now done 172k and is currently being restored. I will try and let you all know if I find anything untoward regarding this topic when the engine comes out.

Andy

[radness 0]

Think someone already suggested this, have you disconnected your thermo switch on the radiator, shorted it out (so max/med fan is on permantly) and sat in traffic to see what happens? - obviously unshort it if you turn your engine off for long as you'll get a flat battery :)

 

Does sound like an airflow issue (like the fan isnt coming on properly) and your temps go way up in traffic....same happened me till i replaced thermo switch, which you've done.

 

Try that and see, when you reach good air (not sitting in traffic or caught behind anything and doing 50mph+) do the temps drop to normal?

 

Sorry, you may have already done this.

[Toad 0]

Stats are some very funny items, Dom's one recently opened at 65 degrees, and there seemed nothing wrong with it visually.

[RDH 0]

Hi Jim, was wondering if you have got this sorted, following a top end rebuild mine does exactly the same with regard to water and oil temps.

 

Sorry if covering old ground!

 

Rich