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Aug 29, 2013 18:13:47 GMT
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Hi folks, hoping someone can advise me.. I have a mk2 GTD which has been blowing cool through the heaters for the past year or so. It blows warm until it's up to temp, then it goes cold. Also the bottom rad hose remains cold no matter how hot the engine gets.
I have tried two different stats to no avail (both OEM quality)
It was sitting at exactly the halfway temp mark all this time so i didn't worry too much. However, today i did a full coolant change as well as a flush and changed my thermostat because i wanted heat for winter this time!
Now the engine just gets hotter and hotter til i turn it off..
Possibilities i can think of are: 1:That safety valve VW installed on the heater hose is opening as soon as the engine gets up to full temp (possibly because the system's over pressurized? I think that valve is to release excessive pressure?) 2: The water pump is knackered and not circulating the coolant properly causing the excessive pressure mentioned above. 3: The heater core is blocked and the flush i just did moved the gunk in the system further into the rad.
Thing is- if the coolant wasn't circulating you'd think it would have overheated a while ago.. There is a king of low pitched whirr on start up that *could* be the coolant pump..
Anyway I'm stuck, any thoughts would be much appreciated!
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Aug 29, 2013 18:30:28 GMT
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cold bottom rad hose normal suggests a stuck thermostat, or a poor water pump.
do away with the heater valves and just put some straight pipe in, test for blockages with a hosepipe running thru different pipes, that will tell you if you have a blockage somewhere.
never rules out a stat tho, thy can and do fail at anytime and any age.
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Aug 29, 2013 18:36:51 GMT
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Hmm yeah well i though it was the stat but i'm now on the third one with the same problems so i don't think it's that.. Is there any way to determine if it's the pump without replacing it?
Not too keen on removing the valve tbh, didn't they put that in to stop coolant exploding in your face when pressure builds up?
Cheers
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Aug 29, 2013 18:48:20 GMT
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not that i know of, for the price of one may aswell fit a new one, if the pipes all flush with a hose.
was a recall to reduce pressure in the heater core as some burst over the passengers feet. never had a mk2 with them still in place tho, they always get removed as they fail with age.
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Aug 29, 2013 20:05:21 GMT
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Ok, I'll give a new pump a shot. Just wondering though, in what way do the pumps actually fail? I mean if the impeller is turning, how would it not pump the water round?
Cool, i'll dump the valve then..
Thanks
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rodney
Posted a lot
https://www.facebook.com/RD-vehicle-transport-and-recovery-services-525622614268010/
Posts: 1,677
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Aug 29, 2013 23:51:09 GMT
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pump or rad blocked,.
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facebook: rodney dean / rd transport
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are you bleeding it out properly each time? could be an airlock
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Pump won't have any fins left on the propeller and you might want to fish these bits out of the block.
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Aug 31, 2013 19:48:35 GMT
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Thanks for all the replies, I'm a bit stuck now.. I was planning to change the pump but it seems near impossible without taking the diesel pump off which i really can't be bothered with.. Maybe S spanners will do it i'll see.
However, the pump seems alright- theres no leaks, the impeller is intact (you can see/feel through thermostat hole) and the bearings don't seem to have any play.. Not sure what to do now, I've tested the rad as best i can by pouring water in the top- It all comes out the bottom. I know it's not the most thorough test but you'd think it'd be really blocked to stop the bottom heating up at all surely?
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Aug 31, 2013 21:33:26 GMT
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Sorry to ask but are you bleeding the system correctly?
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Aug 31, 2013 21:50:54 GMT
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Defo sounds like an airlock in the system
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Aug 31, 2013 22:10:02 GMT
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Yeah, i'm certain it's been bled right, Ive never had trouble bleeding mk2s before. the whole bottom of the rad doesn't heat up, could an airlock cause that?
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Aug 31, 2013 22:11:48 GMT
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Unless there's some trick to bleeding diesels that's different from mk2 petrol engines?
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Sept 1, 2013 10:52:14 GMT
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Nope, nothing different. Just seems very odd that it would start after emptying and refilling the coolant system and give the same sort of symptoms as an air lock
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Sept 1, 2013 11:28:34 GMT
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Remove the stat all together and run it with Flash kitchen floor cleaner (lemon) I have used this to clean systems after mayonnaising has happened
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Sept 1, 2013 12:50:21 GMT
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Hmm, well the bottom of the rad always stayed cold so the only new symptom is overheating.. Does it have to be lemon or is that just your scent of choice? Is laundry liquid as good? That's what i was going to use..
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Sept 1, 2013 14:30:12 GMT
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A dishwasher tablet also works well.
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Life without spanners is no life!
Rover 414 SLI
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Sept 1, 2013 19:37:56 GMT
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Think i've finally figured it out! Tried taking the stat out and running the car- bottom hose heats up fine. So the rad isn't blocked and the pump is working.. However the stat itself is fine too, i've tested it so the only other possibility i can think of is there was an airlock behind the stat.. So now my question is how the hell do you bleed the system? I mean i know how it's usually done and i did that but to no avail. Would it be crazy to drill a tiny hole in the stat?
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Sept 1, 2013 21:13:27 GMT
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I normally bleed mine by leaving the expansion bottle cap off and running the car until the fan kicks in. While doing that I have the heaters on full and keep squeezing the coolant hoses to try and help get any airlocks out.
not sure if that's the common way of doing it? But it's the method I was taught and always seems to work well
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Last Edit: Sept 1, 2013 21:16:00 GMT by roccoguy
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ChasR
RR Helper
motivation
Posts: 10,245
Club RR Member Number: 170
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Sept 1, 2013 21:13:58 GMT
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What brand of thermostat was it?
Stags and even the Mondeo V6s in my signature suffer from incorrect thermostats. The pair of them either have a tiny hole present in the thermostat so as to guide water through, others have a jiggle pin which shuts as the coolant system has been filled. It is surprising for both cars how many systems list them with the incorrect thermostats (both have bypass feet as well, which a few books do not list).
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