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Need some water pump help please guys....

2825 Views 16 Replies 5 Participants Last post by  Fogcity
Ok, firstly, the car is a LHD 2.0 1999 jetta.

It's had some over heating problems, and so far it has had a new rad (previously) and I have put a new thermostat in, although I'm not sure it's working. (NOW TAKEN OUT FOR TESTING)


1) Ran hot and almost boiled. - expansion bottle is blowing out steam/water (no pressure from compression, not head gasket, only pressure through temp. no oil/water mix....)

2) Changed thermostat (not one in there before) and now top hose only hot in first 3-4 inches. bottom hose cold. - Radiator only hot in bottom 2 inches.

I disconnected the rad hoses, and flushed the rad through, including the engine block water jacket, no obstructions, and flowed freely.

As the rad wasn't circulating water, i thought the issue was the rad fan switch, as the fans weren't cutting in. I bridged out the fan switch multiplug, so they ran permanantly, and it ran for half an hour on the drive just fine (bear in mind our ambient temperature is 100 degrees...)

So i drove it today, and it overheated again.... so the only thing left was the water pump. When filled with water (cold) and run, only a trickle of water came out of the top hose from the engine. (the 1" diameter hose that goes backwards, over the top of the plastic housing with the four pin multiplug and two big hose outlets, with the oval 'O' ring into the head, on the left hand end of the head, is a little kinked and restricted....)

So i thought, OK, check the water pump... I COULDN'T FIND IT!! After looking, I assumed the black plastic housing on the side of the head was an electric water pump driven by either 12V or the cam... took it off, and all i could see was what looked like a coolant temp sensor (it could at a stretch be a tiny electric motor of which the impellor has disappeared...)... but there is one of those (temp sensor i presume) in the four way hose junction just down towards the Rad...

I CANNOT FIND THE WATER PUMP!!![wtf] It's got me beat. The fan belt only drives the ac compressor, the P/steering pump, and the alternator... where the hell is the water pump? is it the oval thing on top of the gearbox with the two vertical 'hex' socket bolts on it? (surely not)

I'm not a complete newbie to cars,I 've rebuilt them, raced them, maintained them etc etc, but I just can't put my finger on where the water pump is..

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lol the water pump is driven by the timing belt, so its behind one of those sprokets. The timing belt needs to be taken off (obviously) to get to it.

By the sound of it, you're only putting cold water into your car? No coolant? That can very easily cause overheating. Makes little sense to me, but the reccomended 50/50 water/coolant mix protects your engine for both extremes of temperature, where as pure water or pure coolant does not.

Definitly need to have coolant in there. Not any coolant though... ONLY G12 or Pentosin. That **** you can get from walmart and autozone/advanced is no good. has inexpensive G12 coolant, or you can go to the dealer too if you're in a hurry.

Does it overheat on the highway? If so... More than likely your impellor fins are lodged in your thermostat and melted throughout the system lol
Thanks dude, will check that. Si I guess I'll take the water pump off and check it. jeez... why driven by the timing belt? that doesn't make any sense... (to me I mean, not doubting you...)

The thermostat is out now, so hopefully ( i guess) the impellor has failed... jeez, why is this so hard?

Just please clarify, I know the difference, but you're saying the water pump is driven by the TIMING belt, and not the alternator belt, yes?

Just please clarify, I know the difference, but you're saying the water pump is driven by the TIMING belt, and not the alternator belt, yes?

Correct sir. The timing belt spins faster as RPMS get faster... The faster your engine moves, the more coolant it needs to circulate. Probly their reasoning behind it. However, the accessory belt does the same thing lol but I suppose they thought having the water pump on a toothed belt would be more reliable than having it driven by a smooth serpintine belt.

In any case, I hope this helps!
Thnak you, I'll go lay under it and see how I get on!

OK, so spent all day taking it apart, taking out the water pump (still a f'ing stupid place to put it!)....

The water pump is just fine, no damage, rotates ok, all vanes in place and not cracked or missing....

Car all reassembled, and with the fans still bridged out to run constantly, it wil idle just fine (one mark above 190), but as soon as I start to drive it, the temperature goes up again. I just don't get it, surely with airflow it should run cooler??

Please help me again guys.....

not for sure but have heard of a slug build up if you dont use full synthetic oil 5w30 mobil 1 and if you mix any kind of coolant other than g12 it will gel up inyour motor , a good place to ask this is at as you share the same motor as some of them
Full syn is only recomended... G12 coolant is required, and only pentosin can be used as a substitute.
yes recomended by audi/vw cause they found that in the 1,8t the conventional oil has been boiling and creating sludge and cloging the motor, but they wont tell you that so that you take it back to them to get it fixed. regular oil boils at 350 and some full synthetics are good to up to 475-500 this is why porsche and audi require full syn , could this be a overheating problem for him , maybe ,dont no could be if its been runnig hot its def boiling the oil if its not full syn and if he mixed any coolant other than g12 it is geled up and thats def the problem , a im still new to audi vw and found out that they share the same motor and fluids and when they recomend something its only to protect them aganst any lawsuits not to inform you of there moror . so when you dont take it back to the dealer then you will end up taking it to them broke so they can fix the probem . [teacher] love to try to help but am still learning , i have a TT Quattro and am looking to get the wife a 2000 jetta and thats why i am on this forum. trying to find the problem with them before i get one and found there much like the tt ,but very much a good car just change the timing belt every 60,000 and regular tuneups and oilchange and they run forever
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1. Image fail lol

2. I'm deff feelin the quattro TT, but try to avoid 2000 Jettas... Actually 2000 model year any car really. For some reason, they have more problems than others. You could get lucky and get one thats perfectly fine.

3. I believe you're referring to the older passats when it comes to sludge. Newer (Any MKIV) 1.8T's don't have sludge problems. Sludge isn't necessarily causd by boiling either. When oil vapors mix with water, thats when you get sludge. When winter hits, thats why they tell you to keep short trips to a minimum... When its cold out and you dont let your car heat up enough to boil off any condensation in the motor, it'll create sludge in some ports/hoses/surfaces.

New 1.8T's certainly like syn, I wont argue with ya there. But if you're on top of maintenance and use conventional, I don't see a problem. Especially since our motors run slightly cold at 190 degrees.
thanks and i stand corrected again, as i am still learning and thank for the info on the 2000 ,i will look for a newer year
ok guys. this thing is kicking my ass now. so hoses off, the radiator, and engine water ways run free... with the garden hose inserted. the outlet, where ever that is (top hose, bottom hose, which ever is disconnected etc) runs free with the pressure varying according to what i put in with the garden hose... so assuming free flowing. when it runs, builds temp and overflow in expansion bottle, holds pressure, so not head gasket, and does not pressurise immediately on start up, so again, not head gasket...

water pump is ok. bottom (thermostat) hose is hot for the first 4" or so, but cold (ambient) for the rest.... I know this implies no water flow, but everything is free flowing, and water pump is fine.....

top hose is hot, as are hose to the left hand (drivers) side of the engine.

fans are running constantly, as the multiplug terminals are still brigded out.... BUT the radiator that I can reach through the fans (when they stop running! LOL) is cold cold cold, no temp at all, it's as cold as if it hasn't been running. Is this (the radiator nearest the engine) the coolant rad, or the oil cooler.... i'm wondering now if the oil is getting so hot (if the rad nearest the engine is the oil cooler and that is blocked..)that the (water) cooling system can't take the temperature away from the whole engine....

again guys, please help me out...:confused:
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The BIG radiator is the one for your coolant... I'm actually not even sure if we have an oil cooler... But what you're looking at/feeling could very well be the AC condenser. What kind of hoses are comming off of it? Soft or metal? If metal... Its for your AC or oil. Soft means coolant.

How do you know your tstat is ok?
Thanks Boost. the thermostat is currently removed. i did 'replace' it (it was already removed when i took off the housing to 'replace' it....

i can't see the hoses because of the cowling etc, so next is to strip down the slam panel to see just where the rad hoses go to, and what component is nearest the engine....

sorry, i mean I can't see definitively whether the hoses attach to the 'rad' that i can touch through the fans, or if they go to a 'cooling radiator' (main one) behind the finned component that I can touch through the fans, because of the cowling/mounting plate for the fans them selves....

gotta get dirty hands again i guess.....
Did you get this fixed. I am having a very similiar problem, and I am lost. I replaced the thermostat today, as well as the thermostat sending unit. My radiator hose is cold below, and hot on the upper hose. The car will sit and idle at 190* for about 15 minutes and than it will slowly climb. When you go drive it it spikes to 260* very fast.

On a side note the car was burning a bit of oil so I put some engine restore in with the rest of the oil being Schaeffers synthetic. Could the mixture be causing the car to overheat. It drove fine for several days prior.
I’m going through the same thing on my 2003 2.0 Jetta. Either of you two find the answer?
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