'00 Jetta TDI overheating

sk1pp3r · Jan 11, 2019

I have a 2000 Jetta TDI and have flushed the coolant, replaced, burped, continual interaction with the car for past 2 weeks... yet is still over heats unless i run the heater.

i really need some help.

When i flushed the system I opened up all i could and the bottom drain allowed all fluids to leave via gravity. ran distilled water through with engine running until it ran continually through the return like to over flow bulb. then drained again and gravity fed G12 until stopped flowing and started motor. continued to fill until ran continually through return to bulb. even stood squeezing hoses for an hour burping bubbles out.

yet, my 50 mile commute finds me at temp (190) after 5 miles of driving, then after my midpoint (25mi) the needle rises quickly to the 260 mark. then i hit the heater and it starts going back down. heater on (190) heater off (overheat).

its driving me nuts.

I have: done all of the above as well as look for leaks (finding none), and clean temp sensor connection and ensure good connection. Radiator fans are working, water is in constant flow to bulb. G12 coolant.

I have not: tested or changed thermostat

thank you in advance

BobnOH · Jan 11, 2019

Coolant is not circulating. Thermostat stuck closed or water pump quit or flow is restricted by a blockage or a really weak hose collapsing.
Long shot it could be a small leak in the system, causing it to loose pressure, but this doesn't seem to bother these engines.

JB05 · Jan 11, 2019

Do you see coolant flowing back into the reservoir via the top hose? Simple test for the water pump.

Metal Man · Jan 11, 2019

Was it working ok before you flushed it or were you trying to fix the overheating issue?

sk1pp3r · Jan 11, 2019

response to responses

JB05 - Yes, see flow at the bottle from top hose. when i start the motor i can pull the return hose from the bottle and it will continually flow/circulate.

BobnOH - I will pull thermostat and boil it this weekend.

Metal Man - YES and NO... YES it overheated before but it was because one of the small hoses ruptured and started pissing coolant all over firewall. I replaced the hose and added distilled water. But i figured the coolant is something i never replaced when taking ownership so i did what is recorded in thread. But NO - prior to the pinhole in the hose there was no leak or overheat.

BobnOH · Jan 11, 2019

sk1pp3r said:
JB05 - Yes, see flow at the bottle from top hose. when i start the motor i can pull the return hose from the bottle and it will continually flow/circulate. ....................................

When the car is started cold the thermostat should be closed. IDK if you would see flow, never done it, but I can tell you a pretty common failure in these is the thermostat gets old and lazy. Normally it results in car not reaching temperature.
It's an outlier, but engine oil does much of the cooling, low oil, bad oil, poor circulation can cause overheating. Another stab in the interweb dark, excess friction from damaged internals will also produce a lot of heat.

Nero Morg · Jan 11, 2019

If you have flow, cools down with heater running, and radiator fans are working, check that your radiator isn't face plugged. Lots of crud can get in between the condensor and the radiator.

sk1pp3r · Jan 11, 2019

Will check

Nero Morg said:
If you have flow, cools down with heater running, and radiator fans are working, check that your radiator isn't face plugged. Lots of crud can get in between the condensor and the radiator.

I will check this. It has been windy and i live in leafy area, maybe.

my perplexition is based on that the heated running will cool engine.

will let yall know

Vince Waldon · Jan 11, 2019

sk1pp3r said:
my perplexition is based on that the heated running will cool engine.

Our TDIs are actually pretty efficient little machines, wasteheat-wise, and it turns out that the heater core is often all the radiator the engine requires, particularly during the winter when the heater core is being fed a nice stream of cold outside air.

Nero Morg · Jan 11, 2019

Yeah no kidding, cold blooded turds they are. That's why I'm surprised this one is getting hot. Banking on poor flow of air across radiator.

BobnOH · Jan 11, 2019

Didn't think of that one, radiator failure could cause these symptoms.

WildChild80 · Jan 11, 2019

If you pull the thermostat, you're probably going to break the plastic retainer, I would replace the thermostat and neck while you have it off, worse case you got a new thermostat that you don't have to worry about.

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alex_tdi · Jan 12, 2019

If you break the plastic retainer and the thermostat housing is otherwise still in good shape, you can reuse the housing.

All you have to do:

1) is use a long wire/cable tie,
2) loop it through the top of the thermostat,
3) insert both ends of the wire through the housing until they come out the other side of the housing, and
4) pull on both ends of the wire so the thermostat is tight against the housing (cuz the plastic retainers are broken)
5) mount the housing (with the o-ring/gasket) and bolt it on the engine
6) once the bolts are nice and tight, pull on one end of the wire to remove the wire completely

You might need a few tries, but once you get the hang of it, you won't need to buy a new thermostat housing every time you are inspecting/replacing the thermostat.

I wish a had a picture, but hopefully you get the idea.

csstevej · Jan 12, 2019

alex_tdi said:
If you break the plastic retainer and the thermostat housing is otherwise still in good shape, you can reuse the housing

You might need a few tries, but once you get the hang of it, you won't need to buy a new thermostat housing every time you are inspecting/replacing the thermostat

Why?
It’s cheap to buy and you don’t have to “ try it a few times to get the hang of it “
Just my .02

Nero Morg · Jan 12, 2019

I reused the broken one in mine and my dad's car, and reusing the broken one on the engine I'm overhauling on a stand. Free is better than cheap and it's not really that necessary... Just my 2¢

flee · Jan 12, 2019

Like Nero said. I didn't even know there were supposed to be 'tangs' for several T-stats.

Vince Waldon · Jan 12, 2019

I'm much more concerned about how they warp over time than the tangs, one of which generally survives and both of which are kinda optional.

The sealing surface itself does tend to warp over time, being composite plastic, and the warping usually happens when the thing is unbolted to change the t-stat.

For the 10 bucks it takes to get a new (flat) housing guaranteed not to leak, with fresh tangs to make installing the t-stat easy.... well... it's a no-brainer for me.

WildChild80 · Jan 12, 2019

And it's not like you replace it every oil change, every 100k or 200k miles for 10 bux, you do you but I'mma replace it myself and not worry about it

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mk3 · Jan 12, 2019

My first thought was - plugged and/or fouled radiator. I had this happen to me decades ago before i learned that distilled water and not well water must be used for cooling systems.

Second, the impeller has come loose from the shaft of the water pump and it is not circulating coolant. I had this happen with my 1995 VR6.

D-Cup · Jan 12, 2019

My 2000 Jetta has this same problem. Exact behaviors. Perfectly fine for 15min of driving, highway or otherwise.
T-stat tested ok.
Saw signs of EGR cooler leaking. Did EGR delete.
Then it ran fine for 20min before overheating.
Replaced head gasket. (Head measure out fine, so no need to rebuild/machine.)
The holidays got in the way of my progress on this project of putting everything back together but I’ll chime back in once I get it up and running.

Nero Morg · Jan 12, 2019

Being as it has coolant flow through the return line to the surge tank I'm sure the impeller is working. Or at least partially in tact.

Secondly, I'm not saying you shouldn't replace the tstst hosing ever, just not for broken tangs unless it bugs you. I replaced the one on my buddy's car because his was warped and leaking. So far mines been fine, the tangs are there only to hold the thermostat in place during installation. I'll probably order a replacement hosing when I do the next timing belt.

Nero Morg · Jan 12, 2019

Head gasket would cause exhaust gasses to get into the cooling system. They make kits for checking for hydrocarbons in your cooling system to check for partially blown head gaskets. Cheaper and faster than pulling the head.

STDOUBT · Jan 12, 2019

If I was made of money I'd have this on both my Jettas:
https://www.ecstuning.com/b-iabed-i...-housing-oem-part-038121121/462-001-0017~iab/

ItAintRodKnock · Jan 12, 2019

STDOUBT said:
If I was made of money I'd have this on both my Jettas:
https://www.ecstuning.com/b-iabed-i...-housing-oem-part-038121121/462-001-0017~iab/

No tangs.

Just sayin'.

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Nero Morg · Jan 12, 2019

So does that mean it's broken out of the factory?

wonneber · Jan 14, 2019

Nero Morg said:
Being as it has coolant flow through the return line to the surge tank I'm sure the impeller is working. Or at least partially in tact.

I thought you could take the thermostat out and push on the pump impeller to see if it's loose.

Don't know how hard I would push a plastic impeller.

Nero Morg · Jan 14, 2019

Yes you can. It shouldn't move being as the timing belt is holding the pump still. If it does rotate at all, then your pump is bad.

sk1pp3r · Jan 23, 2019

Resolved

It was the THERMOSTAT.

Frozen solid as a rock. I boiled that thing for an hour and never once did it open by itself or with force. Like it was welded shut.

sk1pp3r said:
I have a 2000 Jetta TDI and have flushed the coolant, replaced, burped, continual interaction with the car for past 2 weeks... yet is still over heats unless i run the heater.

i really need some help.

When i flushed the system I opened up all i could and the bottom drain allowed all fluids to leave via gravity. ran distilled water through with engine running until it ran continually through the return like to over flow bulb. then drained again and gravity fed G12 until stopped flowing and started motor. continued to fill until ran continually through return to bulb. even stood squeezing hoses for an hour burping bubbles out.

yet, my 50 mile commute finds me at temp (190) after 5 miles of driving, then after my midpoint (25mi) the needle rises quickly to the 260 mark. then i hit the heater and it starts going back down. heater on (190) heater off (overheat).

its driving me nuts.

I have: done all of the above as well as look for leaks (finding none), and clean temp sensor connection and ensure good connection. Radiator fans are working, water is in constant flow to bulb. G12 coolant.

I have not: tested or changed thermostat

thank you in advance

Nero Morg · Jan 23, 2019

Awesome, easy $7 fix!

BobnOH · Jan 23, 2019

I've read it's a good idea to refresh the housing as well.
https://www.idparts.com/alh-thermostat-kit-038121121-044121113-p-5578.html

'00 Jetta TDI overheating

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