johnymingle Posted Thursday at 05:14 PM Share Posted Thursday at 05:14 PM A4 2.0 tdi b7 2008.... I have noticed when putting my heaters on, I get hot/Warm air for a few minutes then it turns cool, my temp is normal at 90. My scan pointed to heater circulation flap.......it was indeed knackered so I replaced that. Still the same so I replaced the thermostat thinking it might be stuck open and made no difference.....the top hose gets hot and the bottom is cold..... hoses on the bulkhead to the matrix, bottom is hot and top is half hot and when pried back there's a trickle of coolant. ...... expansion vessel cool to mildly warm with not a trickle in the return.....replaced timing belt 4 years ago and new SKF pump.....always used fresh coolant and its very clean....My gut feeling is the water pump, as the water doesn't circulate, but then i think is it the heater matrix!! Im stumped really, as I would expect a good pump like skf to last longer than 4 years. And if it's the matrix, then why isn't the rest of the engine circulating, (or does it have to circulate through the matrix to make a circuit) I would appreciate some experienced help thanks. Quote Link to comment Share on other sites More sharing options...
alpha omega Posted Thursday at 05:27 PM Share Posted Thursday at 05:27 PM can we rule out an air lock as they can be stubborn Quote Link to comment Share on other sites More sharing options...
johnymingle Posted Thursday at 05:43 PM Author Share Posted Thursday at 05:43 PM Wel I took off the top bulkead hose (the one with a little hole for bleeding) and expecting bubbles but there was nothing. Pulled it right off and coolant was flowing back towards the engine, but a very slow rate. The engine was normal temperature. I held the expansion vessel as high as I could......its like all coolant anywhere isn't moving but its not overheating. I replaced the radiator about 15 months ago. 1 Quote Link to comment Share on other sites More sharing options...
johnymingle Posted Saturday at 07:44 PM Author Share Posted Saturday at 07:44 PM On 10/17/2024 at 6:27 PM, alpha omega said: can we rule out an air lock as they can be stubborn I think so, but you can only get an airlock when there is a flow!! Theres nothing flowing so I've determined it must be the pump......At the end of the day, it's nearly time for a Cam belt anyway, so I've ordered it along with the pump and fitting tools. What is strange is that I don't have an overheating issue! ..... Maybe down to fitting a new radiator last year, and that diesel engines run a lot cooler than petrol ones anyway. 1 Quote Link to comment Share on other sites More sharing options...
alpha omega Posted Saturday at 07:49 PM Share Posted Saturday at 07:49 PM when you said the top hose gets hot and the bottom hose is cold this is why i mentioned an airlock Quote Link to comment Share on other sites More sharing options...
johnymingle Posted Saturday at 07:59 PM Author Share Posted Saturday at 07:59 PM Yes it makes absolute sense, it's a strange one 1 Quote Link to comment Share on other sites More sharing options...
johnymingle Posted Sunday at 06:49 PM Author Share Posted Sunday at 06:49 PM 22 hours ago, alpha omega said: when you said the top hose gets hot and the bottom hose is cold this is why i mentioned an airlock I think it may be the heater core blocked, I'm going to backflush it ..... Quote Link to comment Share on other sites More sharing options...
Stevey Y Posted Sunday at 07:12 PM Share Posted Sunday at 07:12 PM 16 minutes ago, johnymingle said: I think it may be the heater core blocked, I'm going to backflush it ..... Hi I think from memory on most models around that year instead of fitting the Silica bags to the expansion tank they put them in the heater matrix as you have minimal flow it could well be that the bags have collapsed, the heater system bypasses through the heater core so the car gets warmer quicker, you wont overheat because of the primary bypass at the thermostat. Steve. 1 Quote Link to comment Share on other sites More sharing options...
johnymingle Posted Sunday at 08:22 PM Author Share Posted Sunday at 08:22 PM What's silica bags?? Quote Link to comment Share on other sites More sharing options...
Stevey Y Posted yesterday at 10:59 AM Share Posted yesterday at 10:59 AM 14 hours ago, johnymingle said: What's silica bags?? Hi some zoon of an engineer found out that a bag of silicate in the cooling system helped keep the antifreeze from deteriorating, they used to put the bags in the heater matrix but the problem is the plastic bags deteriorate and burst releasing the silicate granules in to the water which blocks the heater matrix, plan B later was to put a large bag in the expansion tank, the end result was the same the granules block the matrix but on my car you had to buy a new expansion tank and possibly a new matrix, the only reason I got away with mine was removing the bag from the expansion tank and flushing the matrix both ways with a jet wash then flush the block with the jet wash, it was just that my mechanic mentioned that some he had worked on had the bags in the matrix so they had to fit a new one. Steve. 1 1 Quote Link to comment Share on other sites More sharing options...
A4B7 Posted 15 hours ago Share Posted 15 hours ago Replace the heater matrix. It's easy enough , you can do it from the drivers footwell, no need to take the dash out or much really. If you're handy it is quite accessible. Quote Link to comment Share on other sites More sharing options...
johnymingle Posted 14 hours ago Author Share Posted 14 hours ago Will the clutch pedal get in the way? I saw a u tube video with the LHD and he removed the accelerator pedal and it didn't look too bad. I've ordered it and a T belt kit, needs done anyway......thanks for the input Quote Link to comment Share on other sites More sharing options...
A4B7 Posted 13 hours ago Share Posted 13 hours ago I did without removing much at all really on a RHD car from the drivers footwell. Good luck with it.. I think I followed a write up from the net . It wasn't a bad job at all if it was I would have remembered. 1 Quote Link to comment Share on other sites More sharing options...
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