1.6d overheating

[CoalRollinMK2]

Hi everyone,
I’m trying to diagnose my 1989 Jetta 1.6d. The car overheated on my way to work, and upon turning it off, coolant spilled out of the expansion tank cap. I observed no external leaks while the car was running. Today I replaced the thermostat and attempted to bleed the system. With the cap off and the car running, the coolant level did not go down so it obviously wasn’t getting through the system. It only went down once I turned the car off after a while. I filled it up again, and upon running the car it remained at the same level. I just tested the old thermostat out of curiosity, and it opened just fine at 180 degrees.
I’d love some assistance on what my next steps should be. Im thinking that since water isn’t getting through the system even though the thermostat is opening, it could be the water pump. Should this be the next thing I replace?
Thanks for any help!

 

[02NBTDI]

It is most likely a blown head gasket.

 

[J_dude]

Pressure in the expansion tank right after running the engine? Rubber glove over the opening and if it blows the glove up like a balloon right away that’s the head gasket, compression getting into coolant passageways. Tested my ‘81 this way and it was blowing up the glove as I cranked the engine, didn’t even start it.

 

[CoalRollinMK2]

Would the test still be valid with how little coolant I have in the system? I can’t add anymore coolant because it just stays in the tank. It’s weird because even if there was air or compression in the system, some coolant should be able to circulate. When I run the car in attempts to bleed the system, the level does not go down at all.

 

[dieseldonato]

Unless the waterpump went out. It won't circulate coolant, or there is a blockage.

 

[CoalRollinMK2]

Ok, I think I’m gonna look through the thermostat housing to see if the impeller is broken/not spinning. I didn’t think it was water pump because I don’t have any visible coolant leaks, but it could be an internal thing. I’ll also check hoses for any visible blockages.

 

[J_dude]

Would the test still be valid with how little coolant I have in the system? I can’t add anymore coolant because it just stays in the tank. It’s weird because even if there was air or compression in the system, some coolant should be able to circulate. When I run the car in attempts to bleed the system, the level does not go down at all.

Yeah either way, if there is compression pressure getting in the system it’s a head gasket issue, whether there is coolant in it or not. Don’t run it long though with low coolant.

This does kinda sound like waterpump though. How much coolant did you lose? Are you sure it’s low? I mean, how do you know how much is actually in there?
I’m not it’s if it’s a problem on those but on early MKIV TDI’s the water pump impellers were sometimes plastic and could strip out so they would turn on the shaft, so checking that it is turning with the pulley makes sense to me.

 

[CoalRollinMK2]

I drained the thermostat housing and the hose it connects to, which was a lot of coolant. I added back about a half gallon of distilled water that eventually went down when the car was off (weird, didn’t budge when the car was running.) Then there’s the other half gallon that’s in the expansion tank but hasn’t gone down at all, even with the car running.

 

[dieseldonato]

You may have to jack the one side of the car up to help it, been so long since I had my 86 I can't remember what the procedure was.

 

[CoalRollinMK2]

Thats interesting actually, I had the passenger side in the air when I was doing all this. Maybe I’ll run it with the drivers side in the air, as that makes more sense for coolant flow, and see if it makes a difference

 

[Prairieview]

Ya, and maybe you will get smart and take the top radiator hose off (at the radiator) and hold it up in the air and fill the cylinder head and block through it. Once it stops taking more anti-freeze, quickly lower it and get it on the radiator connection. Use a funnel or whatever. I did not realize common sense is so scarce.

 

[fatmobile]

If there isn't coolant flowing through the small hose and streaming into the reservoir,
then that hose is plugged.
There is a restrictor in that line,
you can feel it not far from the reservoir.

Some people cut it out but that can cause heavy flow into the reservoir that splashes against the check valves in the cap and opens them.
Someone made a deflector to keep that from happening.
Some people back flush it, then put a filter in the line before it, to help keep it from clogging again.

Real common cause of overheating, cheap and easy to fix.

Taking the top rad hose off and making a mess isn't the smart move. when all the air will rise toward the reservoir if it is flowing correctly.

 

[CoalRollinMK2]

Hmm, I did notice some swelling in that small. hose that connects the top of the reservoir directly to the radiator. I’ll check it out, thanks!

 

[CoalRollinMK2]

I cut out that restrictor, and it was super clogged. I reconnected everything, filled it up with coolant, and now I can actually see the flow of coolant from the return line entering back into the reservoir. The car held temps at idle for a long time, and the heater started blowing hot air again. I'm gonna completely flush the system tomorrow and tighten everything back up, hopefully this solves it. This was definitely one of my issues though. I'll figure out what to do about the restrictor soon, just want to get it back in the garage first. Thanks so much for the help! Will update.

 

[1854sailor]

Ya, and maybe you will get smart and take the top radiator hose off (at the radiator) and hold it up in the air and fill the cylinder head and block through it. Once it stops taking more anti-freeze, quickly lower it and get it on the radiator connection. Use a funnel or whatever. I did not realize common sense is so scarce.

Please chill a bit. There's no need to be so snide and unwelcoming to a new member. We're here to help.