Club G40 Forum
Technical => Engine and Transmission => Topic started by: GSBellew on March 04, 2010, 12:01:57 am
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My G40 has me a bit stumped at the minute :-[
I had to take it for a 50 mile motorway run a while back, it was perfect the whole way until I got to the end of the motorway, as soon as I slowed down from motorway speeds the coolant light came on, I still had heating and the temperature was not unusually high, luckily I was as far as I needed to get so I was able to park up and leave it.
Two days later I had to do the return trip, so I topped the coolant up and set off, the exact same again, perfect the whole way until I slowed down at the end of the motorway, light on again.
I was a bit annoyed so just pulled it into the garage and have left it alone till now.
I gave it a good checking over tonight, the oil and water are not mixing and there are no bubbles coming up into the expansion tank with the engine running, I ran it for a while and everything seemed fine, nothing unusual from the exhaust, and no signs of leaks anywhere, but when it hit temperature and the fan kicked in a little bit of coolant came out of the expansion tank overflow :-[
I'm not sure if this was just because the level was slightly over the max level as I know I had accidentally put a bit too much in or if this is where all the coolant has been going ???
Does anyone have any suggestions as to how to figure out where it has been going or what to check next?
Any suggestions really appreciated!
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check the condition of the seal on the header tank cap, or just replace the cap anyway as they're not expensive.
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Also check the water junction at the right hand end of the head, the o-ring is shaped into an oval, i've had a few of these go on various polo's inc the g40. One occurance was that the plastic water junction had cracked.
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yeah - the thermostat housing ages badly!
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Thanks for the tips, I have a new header tank cap on order which should be in tomorrow morning, I'll check the water junction when I get home, would I be as well to just get a new one and new thermostat too?
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Only got a chance to work on this today, unusual way to spend Saint Patricks day :D
I drained and flushed the coolant system, then refilled it bled it and fitted the new cap, ran it up to temperature a few times and it seems fine, I could not do a road test as the tax is up at the minute and being a bank holiday I couldn't do anything about it today.
I think I might still fit a new thermostat and housing anyway and then just keep an eye on it ???
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This has me completely stumped, I had come round to thinking it was the headgasket, but before doing it I decided to change the thermostat and those O rings, found that the one at the head was in very bad shape and was showing signs of having leaked at some point, thought I was on to a good thing so I changed them. Ran it for half an hour at fast idle and it seemed perfect, fan kicking in and the temp dropping as it should
Changed them and took it for a run, perfect for about 20+ miles untill I decided to push it a little on the motorway for a few minutes after I let off the temp gauge started climbing and kept on going, red light on and I stopped, the cooling fan was not running and it had pumped a bit coolant out of the reservoir, I shorted the fan and limped on slowly as I was nearly home, the temp would drop to 100 and go back up to 110 then back down, into the garage, took the shorting wire for the radiator fan out, plugged it in and nothing even though it was a new sensor and working earlier!
I'm lost, do I just take the head off now?
Its had:
New fan switch
New Header tank cap
New Thermostat
New O rings on the housing
Help please!!
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I had a kind of a weird problem like that a little time ago and it was the most unlikely to happen scenario! In my case it was the exhaust manifold seriously leaking exhaust gases! It had the nearest cylinder blowing hot gases directly to the thermostat housing and that really pushed the temperature sky high. The bolts from the exhaust looked fine but as soon as I pushed them they snapped. And when I got the gasket out it was burned at that point! So I am just saying, do check for the impossible before you do the head gasket! The oil pump not working could cause the temp in the water or a small leak from the water pump! My mechanic has a small manual pump with a gauge that connects to the expansion tank and you can pressurise the system to see if its leaking, you could try one of these!
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just run a simple compression test on your cylinders aswell, that should tell you if your head gaskets gone.
all of this happened to me not so long back and i ended up changing everything but it turned out to be the rad fan was not operating properly and wasnt staying on for nowhere near long enough.
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I took the thermostat housing off again today and found it had cracked near the seal on the cylinderhead, so not sure if that was a cause or result of last nights high temperatures.
I've ordered a new housing and the screws / bolts for it.
I'll try a pressure test on it tomorrow too, would one of the halfords pressure testers be good enough?
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Just did a compression test.
I got:
Cylinder 1 8.5 Bar
Cylinder 2 9 Bar
Cylinder 3 8.5 Bar
Cylinder 4 9 Bar
According to the Hanyes manual new is 8 to 12 Bar with the wear limit being 6 bar and a maximum pressure difference of 3 bar between adjacent cylinders.
So does that say that the headgasket should be ok as I am not getting low compression as such or oil in the water or water in the oil?
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when my head gasket went, cylinders 1 2 and 3 read 10.5 bar (150 psi) and cylinder 4 was just over 7 bar (100 psi).
my engine is a 1341 with wossnor pistons i dont know if that changes the compression though.
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when my head gasket went, cylinders 1 2 and 3 read 10.5 bar (150 psi) and cylinder 4 was just over 7 bar (100 psi).
my engine is a 1341 with wossnor pistons i dont know if that changes the compression though.
Compression ratio has nothing to do with a compression test mate.
I'd say the figures that GSBellew got were ok, perhaps a tad on the low side but that could just be the gauge used. Obviously a very low reading or on one or more cylinder like Liam had would show there was a problem.
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Just a thought, I see you say that you've flushed the cooling system but did you take the rad out to give it a real good go? It may pay to reverse flush the radiator particularly if it's the original as they do silt up over time. I reckon it's also worth doing the heater matrix (pipes disconnected) then reflush the engine (thermostat out) to give it all a really good clean.
It'll only cost you a bit of time (apart from another bottle of antifreeze!) rather than keep replacing bits uneccessarily, might be worth a try?
Good luck.
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when my head gasket went, cylinders 1 2 and 3 read 10.5 bar (150 psi) and cylinder 4 was just over 7 bar (100 psi).
my engine is a 1341 with wossnor pistons i dont know if that changes the compression though.
Compression ratio has nothing to do with a compression test mate.
Compression ratio DOES affect compression test results, as does the cam profile and cam timing -as well as the obvious sealing ability of the rings/valves/headgasket etc.
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Sorry to have spoken out of turn yet again Andy.
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Sorry to have spoken out of turn yet again Andy.
Don't chat shit then?
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Who asked you for your input? Shut the fuck up Pete.
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Just a thought, I see you say that you've flushed the cooling system but did you take the rad out to give it a real good go? It may pay to reverse flush the radiator particularly if it's the original as they do silt up over time. I reckon it's also worth doing the heater matrix (pipes disconnected) then reflush the engine (thermostat out) to give it all a really good clean.
It'll only cost you a bit of time (apart from another bottle of antifreeze!) rather than keep replacing bits uneccessarily, might be worth a try?
Good luck.
Yeah I had it out when I was changing the thermo switch and gave it what I thought was a very good cleaning out with the hose, might give it another go though ???
I've the new thermostat housing just waiting for the new elbow which should be in tomorrow so I will see if it sorts it, after that I can only think of the water pump maybe not circulating the water around so the water in the radiator may be cooling which is why the fan is not running but the water in the block is not getting cooled?
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Ok,
I changed the housing and refitted everything, then found a leak where the bottom radiator hose connected to the thermostat housing elbow, got a new pipe today and fitted it, no leak now. Filled and bled the system and ran it up to temperature in the garage, it got pretty hot (indicated 100+ before the fan kicked :o
When it did it cooled down quickly, so I took it for a spin on to the motorway, the gauge sat at 110 the whole way (about 5 miles) I stopped before doing the return leg, still 110 indicated, but checked the engine bay no cooling fan running ??? top pipe to radiator was hot, bottom & the radiator itself cold, thermostat is new.
I did the return run and the temperature stayed pretty much constant at 100 to 110, thought it was ok if a bit hot and confused about the fan, but when I got home it had lost some of its coolant still no radiator fan, let it idle and the fan came on ???
I am wondering if perhaps the waterpump is not circulating the coolant which is why the engine is hot and the radiator is cold? At idle gravity may be enough to make it circulate which could be why the fan comes on at idle but not on the road?
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It's worth checking for sure! Presume the system has been thoroughly bled?
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I bled it by opening the white plastic screw on the valve at the heater matrix / fan setup with the interior heating setting on 'hot' that should do it shouldnt it?
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I usually bleed it with the header tank cap off, wait until the thermostat has opened, then put the cap back on and bleed from the heater matrix.
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I'll try that way tomorrow.
I changed the water pump today, the impeller was ok, but the O ring was fecked and it looks like it had been leaking at the bottom of the pump.
(http://i115.photobucket.com/albums/n311/gsbellew/G40/IMG_0529.jpg)
(http://i115.photobucket.com/albums/n311/gsbellew/G40/IMG_0530.jpg)
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Still the same, but not as bad if that makes any sense?
Its staying cooler than before, sub 100 most of the time still losing a bit of coolant though ???
I noticed the fan is not kicking in till over 100 and is only hitting the low speed, it is a new VW thermo switch should I assume its faulty or suspect the black sender of giving a higher reading then it really is? I'm more inclined to suspect the thermo switch myself ???
I also did another compression test when warm like it says in the instructions (did it cold last time as I had no thermostat housing at the time so couldn't run it to warm it up.
I got 10.5 Bar / 150psi on all 4 cylinders so the head gasket definitely should be ok, could it just be the fan not kicking in until it is too late and allowing the temperature to get too high? Its also not running on when the car is switched off like it used to, the fan is working when shorted out.
I'm thinking out loud now, would it be worth doing some sort of flush on the radiator, in case its blocked or partially blocked ???
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sound like the rad could be blocked, especially under where the sensor goes. Its shallow at that point and easily silted up
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sound like the rad could be blocked, especially under where the sensor goes. Its shallow at that point and easily silted up
What's the best way to check / fix that if thats what it is?
Take it out again and use the hose or one get of the coolant system flush additives? ???
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flush rad with it off and the sensor out i'd say
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when i had this problem my rad fan was to blame, it worked but not as it was supposed to, i noticed that straight away when i put another rad fan on, might be worth changing it mate i got a second hand one from volksmagic for £25.
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Just a thought, I see you say that you've flushed the cooling system but did you take the rad out to give it a real good go? It may pay to reverse flush the radiator particularly if it's the original as they do silt up over time. I reckon it's also worth doing the heater matrix (pipes disconnected) then reflush the engine (thermostat out) to give it all a really good clean.
It'll only cost you a bit of time (apart from another bottle of antifreeze!) rather than keep replacing bits uneccessarily, might be worth a try?
Good luck.
Remember I suggested this before, I reckon its got to be worth a go.
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Just a thought, I see you say that you've flushed the cooling system but did you take the rad out to give it a real good go? It may pay to reverse flush the radiator particularly if it's the original as they do silt up over time. I reckon it's also worth doing the heater matrix (pipes disconnected) then reflush the engine (thermostat out) to give it all a really good clean.
It'll only cost you a bit of time (apart from another bottle of antifreeze!) rather than keep replacing bits uneccessarily, might be worth a try?
Good luck.
Remember I suggested this before, I reckon its got to be worth a go.
Saw your suggestion alright and it was what had got me thinking about re-flushing it properly.
I flushed and reverse flushed the radiator with the hose, then put it back in and ran some radiator flush through it, I decided that for the €1.82 it cost in Halfords with the trade card that it had to be worth trying :D
I had to run it without the thermostat in to circulate the flush around the system, then flush with water (flushed rather dirty looking water out of it!) and run it with water and no stat to rinse it, rather than leaving it sitting on idle for ten minutes I took it out for a run and it didn't loose a drop of water, ran very cold obviously due to the lack of the thermostat, so I won't really know till tomorrow when I drain it and put the thermostat back in if its going to be ok or not.
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How did you get on with this in the end? This is pretty much what I've been experiencing.
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Thought I had it sorted after reflushing the radiator etc, was fine for a 200 mile motorway run but I pulled over to take a call and it pumped the coolant out of the overflow :(
I think the new thermoswitch is screwed too, as its not switching speed one until over 100 degrees and is not switching the high speed on at all. I did the return journey the next day with the fan wired to run constantly and it was perfect and its not lost any water since once the fan is running.
So I'm not sure if I have a borderline headgasket or a dodgy thermoswitch, its back in the garage for the minute as I've not had time to do any more on it :(
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Well I changed my radiator and took the car down the motorway and temp went north of a 100 degrees straight away so I still had the problem. I will say that the new radiator appears more efficient as the temp dropped quicker than with the old one on. However the temp was still going too high so I booked the car into the garage down the road from work for them to do a leak down test. They confirmed the headgasket had gone which was the only thing left along with the water pump which is less than a year old.
I whipped the head off on Friday night and I've picked it up from the machine shop after a skim. The headgasket appeared fine but there was obviously a small amount of water getting into cylinder three. I'll get some pictures up before I put the head back on. Hoping it will all be tickety boo when I get it back on. Might be worth your block tested.
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Just spent a while reading this but if it was still losing coolant it might be the water pump itself. I replaced mine a few months ago, put all new coolant and water in etc and i kept loosing coolant after long motorway travelling. I kept topping it up and then one day i found where it was lekaing from. It was the pump itself. I asked vw to have a look, only as it was a new pump with new o-ring. They had a look, changed it as it came under warranty and they said that in the pump there is a bearing and if it isn't sealed correctly then it will leak. The seal on the bearing had failed on mine and this was the problem.
Of the last 2 things i have bought from vw (in line fuel pump and water pump) both have failed on me but luckily they came under warranty.
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humm... i've had a very mild coolant loss ever since i first rebuilt the G ...
(which turned out to be just ths charger seals that were causing it to smoke... not the HG at all but did the water pump at the same time genuine vw jobby)
going to change mine now along with the rad and see how we get on! anyone know if the rad is G40 specific?
also are the thermostat housing collar that runs to the rad pipe available from vw? never got it sitting 100% flush after replacing the housing and stat...
cheers Ad
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Yes, rad is G40 specific, 867 121 253 AB.