Cooling Problem

[dieselsnowmobile]

My 91 VW NA Diesel Jetta will not cool. I have replaced the radiator and now the thermostat with an 80C. Right now, I start up the engine, it will slowly warm up until it gets too hot I have to shut the engine off. I cannot feel hot water in the hoses much past a foot from the engine. My heater will not even put out hot air. I have replace several thermostats before in the past, I feel like I did it correctly. I have no external leaks either. The only thing left is that the water pump just is not pumping. Has anyone ever ran into this before? Most of the time, water pumps go bad when they start leaking and the bearing is shot, but I have not heard of one just not pumping. I have topped off the coolant several times trying to get as much air out of the hoses I can. My only thought was that there might be air around the pump to the point where it cannot circulate the coolant. Any ideas or thoughts are appreciated. Thanks.

[82vdub]

There have been people that have had the impeller slip on the shaft of the waterpump, and it doesn't pump any coolant. Sounds like you don't have any coolant circulating. Do you have any water squirting from the small hose going to the overflow jug? You should have coolant coming out of that. If you don't, it may not be circulating.

[dieselsnowmobile]

Thanks, that has to be it. I should at least be getting water to my heater core no matter the thermostat position. I have the newer style sphere holding tank and I do not believe I can see the water coming from the little hose. I know what you mean though, I definitely could see it on my old Rabbit.

[DanHoug]

there is a restricter in the small hose of 'modern' diesels of your era... i pulled mine out so i could get a better flow, visually if nothing else. not sure why it is there and mine is fine without it.

but if i had to guess, i'd say you might have head gasket problems causing your lack of heater core heat and overheating... air being pushed into the system.

-dan

[Quantum TD]

I'm guessing that restrictor is clogged. I've seen it all the time. I drill out most of it, and then crush the rest and pull it out with a hook. It's about the only thing that can account for rapid boil-over after an initial start up.

Start there and post an update.

[dieselsnowmobile]

I replaced the pump, and so far so good. Sure as heck wish I would have just done it 2 months ago when I replaced the timing belt, would have saved me a lot of time, basically did it all over again.

What exactly is the restrictor? While I had it all apart, I flushed every hose 6 ways from Sunday. I also flushed the little hose going to the holding tank as well. I also filled the cooling system from the tank, but I took the upper radiator hose off at the head so that I could make sure the block was full of coolant, and then topped it all off after attaching the hose back to the head.

[Quantum TD]

The restrictor is in that small hose that returns to the top of the overflow tank. It tees into a larger upper radiator hose that connects the head to the top of the radiator. It's inside the hose. You'll see a bulge in the hose right before the tank (like a snake digesting a mouse). Remove that from the line by drilling it out and removing the rest of the carcass. Then you'll be sure that a minute piece of crap won't plug it up and blow either your head gasket, the heater core, or any number of hoses.

I had one clog with a tiny bit of silicone that someone used to install the water pump. Blew the heater core thankfully, and saved the head gasket.

[dieselsnowmobile]

OMG! I did not know that was even there, it is gone now. It is not in my 89 Jetta. Well, that pretty much wasted my Saturday replacing the pump. The radiator was shot and while I replaced the thermostat, I replaced the two hard to get to hoses, so that was not a complete waste. Thanks for the info.

[82vdub]

Is the problem resolved and was it the pump, or the restrictor in the line?

[dieselsnowmobile]

Well, I am not a 100% sure, but pretty cure it was the restrictor in the line. When I replaced the pump, it looked fine. I could not get the pump turbine to spin on the shaft at all. The edges of the pump were wore compared to the new pump, but that was probably just normal erosion from pumping. Since the pump looked to be good, I flushed all hoses with the garden hose including the little line to the holding going to the radiator hose (which I did not flush while I replaced the thermostat). When I put it all back together it worked. I also filled the system differently from when I replaced the thermostat by undoing the hose to the head to make sure the engine got full of coolant. After putting it all back together and working, I checked the forum and saw the post on the restrictor, so I went out and drilled it out right then. Since then, no troubles, drove the car 140 miles on Sunday with the AC on full blast, no issues (as long as the AC was on). I have another issue where the radiator fan will not come one at all unless the AC is on. When the AC is on, the radiator fan works great, but never seems to come on unless the AC is on. But that is another discussion, probably the sensor on the radiator.

[Quantum TD]

Rad fan switches are cheap. Head gasket jobs are not. Spend $20-30 on a good WHALER 87C fans switch. Check your fuses and jumper the fan switch plug to make sure that everything is working.