Over heating and no circulation problem

[snail_on_skunk]

Hello, having a slight issue with my car and cant work it out! They usually say if you say it out load it helps, so here goes, just wanted to pick people brains and see what others think.

I have a mk3 1.8t AGU and its over heating and i cant get to the bottom of it. Ive removed and checked the thermostat, that opens fine when in hot water, coolant temp sensor shows the correct tempreture on the dash and when using measure value blocks (VAS PC) the ecu is reading the same tempreture, i thought it might be the coolant pump (which i changed less than 2000 miles ago) so removed that and was in perfect condition. The car will literally get to 90 degress in about 5 minutes from cold start and thats just normal driving, and no water is circulating, to the point where i cant take the coolant temp sensor out on the side of the head and no water/coolant is in there and when the dash is telling me the coolant is at 90 degrees, there is no hot air coming out of the air vents when cranked up to full heat on max fan speed. I also removed the radiator to check if it was blocked and thats clear also.

It cant be the way ive routed my coolant pipes as it was working fine up until a month ago, car has had the engine for about 6 months now(will post some pics of engine bay soon) any one got any ideas of what could be causing it to over heat?

[topher]

when you had the pump out did you grab it by the gear and twist hard on the impeller? I've seen them come out looking fine but with a bit of force (which is what the belt is going to be doing) the impeller spins on the shaft

[snail_on_skunk]

when you had the pump out did you grab it by the gear and twist hard on the impeller? I've seen them come out looking fine but with a bit of force (which is what the belt is going to be doing) the impeller spins on the shaft

Ye, gave it a good turn, completely stiff, put it back in my box just to keep as a spare

[topher]

thats a weird one then, going to have to trace the flow. if you're sure everything is plumbed in right i'd probably start with the basics and bypass the heater matrix. then pull the thermostat/housing back off and crank the engine with a hose pipe in the header tank to see if the pump is doing anything, then put the housing back on without the stat and pull each hose one at a time down the system to see where the flow stops.

you not losing any coolant at all?

[snail_on_skunk]

coolant level drops right to the bottom of the expansion tank and stays really low, light comes on, but as soon as i leave it to cool down and release the pressure, bubbles back up and sits at level again. Based on that its giving characteristics that the head or block isnt letting coolant through and its just building up pressure before so. Ive brought some audi engine flush that i had left over when i left my old work, will run it tonight, then stick the hose on it and see if im gettin flow all the way through or find where its stopping or whats clogging it up?. worth all the hastle in the long run though, hopefully.

[topher]

keep us updated i'd like to know what you find on this one!

[snail_on_skunk]

think ive figured it out! removed the thermostat and refitted the pipe and instead of filling with coolant, used the coolant flush liquid i had lying around. Hoped that this being alot thinner would push out any gunk clogging up the pipes incase i checked them wrong, engine once again overheated but because the liquid was thinner it started seeping out one of the joints, the pipe that goes between the coolant flange on the side of the head to the heater matrix, which must mean that the pressure from the coolant pump is stoppping there because of a blocked heater matrix. Never had to change one before, and know its quite long winded to get the dash out as it is, so tomorow, will take the car to work (really slowly as its only round the corner) remove the pipes that go to and from the heater matrix and plum in 2 pipes and a electric water pump i have in my box (the aux pump that came off a S3) and a little snap on battery. this should hopefully not work and prove its the heater matrix, if not, then im out of ideas!  wish me luck!

[topher]

like i said before just bypass it, pull the hoses off the matrix and join them with something. i've had to hacksaw the end off a vw wheel nut tool to use as a joiner to get me out the sh!t in the past
i'd not drive it dude, 100 degree coolant bursting out on to your legs/feet is gonna hurt.

[snail_on_skunk]

well seen as the 2 pipes i have at the moment going to and from the heater matrix are made out of 4 pipes and 2 joiners (cause i couldnt find any pipes the right shape to go from the 1.8t to the mk3 heater matrix neatly) ill remove it, mix and match them in different shapes, and see if i can loop it back. thanks for the help dude, let you know tomorrow how i get on!

[danny_p]

usally it's a knackerd water pump.

blocked rad,  duff thermostat.

take the stat out and try it ( amazing how meany are DOA )

the hardest one i've ever had to find was weeping Head gasket     engine showed no sings of headgasket fail so no one ever sniff tested it but every now and again it'd blow some air bubbels in teh coolant that would upset the pump