What Should Water Temp Be

[gmcjetpilot]

How do I check the thermostat? Is 172F (78C) OK? It could be a sensor or sending unit issue. I assume REGEN is restricted at low temps, that is why I ask because I had REGEN and DPF issue recently (which I think is resolved).

I have a SCAN Gauge and know the exact Temp. The Dash Temp is always locked onto the 12 O'Clock position over a range or operating temps. My past historical normal temp on warmish days was 192F. Now after oil change I am running in the mid 170's. Could I have a bad thermostat? WT is still showing straight up on dash (which it always does over a range of wide range of temperatures).

I have seen 200F in stop and go traffic on hot day, but went down as soon as I was moving again..

I would not worry about it normally, but long story short had a DPF, Throttle Actuator issue (dash lights including check engine light on). I resolved it I think. Faults were cleared but DPF light remained on. Then DPF light on dash went out after 1.5 hours of driving +75mpg, I have not driving enough to detect a regular regen at slower speeds.. Not sure if I had a REGEN or just hard driving did it. I normally drive like old man, speed limit or 5
under limit.

I don't want to fix it if ain't broken. I am going to monitor the REGEN status and see if it does it normally.... If it does REGEN.

 

[turbodieseldyke]

Is 172F (78C) OK?

Too low. Should be 87C (188F)

 

[DrGERTol]

The original t-stat in our '11 wagon started to fail in a similar fashion last summer/fall. They don't last forever. If you're not measuring approx 87C/188F coolant temp at highway speed, you're likely ready for a new t-stat. --g

 

[TDI-Pete]

Replaced my t-stat last fall. 2010 jetta tdi. It's a lot of work and not easy to do. Made my own tools just to get it done. Would never do it again.

 

[ksing44]

I had my thermostat replaced at ~ 195K miles. Do the "plastic pipe" too.

 

[Chef-CJ]

I would only think about doing it yourself if you're broke. I did mine (because I'm broke) and it sucks terribly. Took hours, had to have my neighbour fabricate me a tool to fit, just overall sucked. But $90 in parts and coolant versus a nearly $1,200 quote was a no brainer for me.

But you do need to get out done ASAP, because if your car doesn't get warm enough, it won't Regen

 

[Mrrogers1]

If you are under warranty and for a good long while, you may be able to get the thermostat replaced under warranty. They did mine because it was found to be faulty/failing and they'd done a couple DPF already on my car.

 

[gmcjetpilot]

All great answers.....
e,
What special tool is needed?
What is the plastic pipe?????
Why is job so hard? (see edit below)

$1200 mentioned above ouch...

I changed a lot of thermostats in my day on other cars, Chevy, Subaru.... took an hour, less than $20 in parts. I am guessing the VW TDI thermostat replacement is fully German complicated mosaicist job...

EDIT: I see what you mean. Good grief that is a lot work... One video talks about service position which removes front body parts for easier access. I do see some special tools, stubby triple square, wobbly extension, make a triple square tool...

 

[DrGERTol]

Item 21 here: https://volkswagen.7zap.com/en/usa/golf+variant+sportwagen/gov/2010-685/1/121-121060/
VAG part number 03L121065T: https://www.vwdirectautoparts.com/oem-parts/volkswagen-connector-pipe-3l121065t --g

 

[gmcjetpilot]

Item 21 here: https://volkswagen.7zap.com/en/usa/golf+variant+sportwagen/gov/2010-685/1/121-121060/
VAG part number 03L121065T: https://www.vwdirectautoparts.com/oem-parts/volkswagen-connector-pipe-3l121065t --g

OK so the coolant pipe is metal or plastic. Is this the upgrade mentioned above. Cheers.

 

[gmcjetpilot]

WHAT ABOUT CHANGING THE TEEMP PROBE FIRST? There is something odd about what is going on. It seems to warm up normally but does not get to the 192F I have known as normal for years.

Is 10F or 15F low bad if it Regens? I know Diesels need to be hot to run right.... and as far as inhibiting Regen we shall see.

So I got a cost from dealer (which I am not going to) of $650 with parts, by diagnostics is $175. so almost $900 with tax (which is shy of 10%).

I have a call into my Independent VW shop. They know TDI's including mine. Even if price is same I'd go to them first.

As far as warranty my Diesel Gate warranty of 4 yrs has expired. It is a 2010 so we are unlikely to get anything from them.

I looked at the video and I think it is doable DIY. This is a second car so it can be down for awhile. I am likely to replace more than the thermostat as well, TEMP SENSOR, Hoses, the coolant pipe..... So take it apart and order parts. Before I do anything I want to make sure it is the thermostat.

 

[Mrrogers1]

WHAT ABOUT CHANGING THE TEEMP PROBE FIRST? There is something odd about what is going on. It seems to warm up normally but does not get to the 192F I have known as normal for years.

Is 10F or 15F low bad if it Regens? I know Diesels need to be hot to run right.... and as far as inhibiting Regen we shall see.

So I got a cost from dealer (which I am not going to) of $650 with parts, by diagnostics is $175. so almost $900 with tax (which is shy of 10%).

I have a call into my Independent VW shop. They know TDI's including mine. Even if price is same I'd go to them first.

As far as warranty my Diesel Gate warranty of 4 yrs has expired. It is a 2010 so we are unlikely to get anything from them.

I looked at the video and I think it is doable DIY. This is a second car so it can be down for awhile. I am likely to replace more than the thermostat as well, TEMP SENSOR, Hoses, the coolant pipe..... So take it apart and order parts. Before I do anything I want to make sure it is the thermostat.

Might as well do the alternator while you are there. It's another HUGE PITA like the thermostat and is accessible while torn apart for the thermostat.

 

[turbobrick240]

Be sure to use an OEM t-stat, you don't want to digging back in there a year or two later because of cheap parts. You could try blocking the radiator temporarily with some cardboard to see if you can get the temp to come up(t-stat- vs. temp sensor). I wouldn't run the AC like that though.

 

[oilhammer]

Don't do that. The intercooler is in there, too, and you'll first cause the ECU to start backing off output because the IATs start going too high, and eventually it'll flag a DTC for "charge air cooling efficiency" and put the engine in limp mode.

 

[TDI-Pete]

I did mine without removing the front end to the service position. Also, did not remove the oil filter housing. Very challenging as mentioned. Be sure to get the O ring gasket, it might be separate. The tool I had to make for the job was punching out a tripple square from the socket, die grind it short, and glue it into a small 1/4” open end ratchet wrench. Do remember how you wiggle the old one out, as I forgot, and squeezing the new one in was a challenge. This is also a good time to clean your EGR valve, and if you have the time, the intake. Hose clamps are handy for the coolant lines. You will also need a gallon of coolant to add after.

 

[turbodieseldyke]

Be sure to get the O ring gasket, it might be separate.

Get an extra one, in case the first one gets pinched.

 

[gmcjetpilot]

Great comments....

1) Went to my trusted independent VW Shop, Wolfsburg VW Audi Porsche Memphis. Talked to Jim one of two owners and experienced (decades) VW mechanic. He did not seem too concerned with my indicated Temp 175F. I have read other threads and normal summer is 190-200F (approx). So I realize I am denial. I have a big trip end of July so I have to make a decision. My past car mechanic experience faulty thermostat in gasoline cars causes high temps not low...

2) Good advice on getting OEM genuine parts. As far as other components, like alternator, may be or not. I will inspect it. At some point throwing parts at it may not make sense.

3) The Bentley manual is useless or I am confused. For 2.0L CJAA Diesel section (it also shows gas engines), the manual shows a traditional in the block round thermostat type with a housing over it? I thought it was plastic four hoses nipples thermostat that bolts up behind OIL housing? (See below). Are there two thermostats? I see two part numbers: 03G121113 (round metal), 03L121111AC or 03L121111AM (plastic 4 house nipples))

 

[DrGERTol]

See my post #9, above. -AC was the original VAG part number, which was dropped in Jul '22; current is -AM. --g

 

[gmcjetpilot]

See my post #9, above. -AC was the original VAG part number, which was dropped in Jul '22; current is -AM. --g

Thanks again. Appreciate your reassurance. The Bently manual is wrong. I'll get the AM part number.

 

[06bluebeetletdi]

I just did the thermostat on my passat tdi while replacing the oil filter housing and then did it again because the new oem thermostat was stuck wide open. If it were me, i would put the new thermostat in hot water to verify it opens and closes correctly.

 

[gmcjetpilot]

I was never a professional mechanic but have been wrenching since I was 16yo on my cars.

Funny thermostat reminds me of my parents. When I was young I fixed a many thermostats and would test the old one and new one. My MOM was pissed I was using her pan and food thermometer to do my test. She was right of course. Hi Mom and Dad (both passed on long ago).

 

[gmcjetpilot]

Well It is fixed, a month ago. I had Wolfsberg do it. Cost $500 all in parts and labor. They underbid. They bid it on 2.2 hours labor. It took 5 hours. They honored price. They are a fantastic Independent Shop. NOW water temps are 198F. My old norm temp was 192F. When the thermostat failed open, it was 172F. So glad I did not do this job...

 

[McGuirk]

Thermostat sure is tough, but for how long they generally last, how cheap the parts are, and that it is DIYable we can't complain. I'll take working on these cars any day over the crap they are forcing down our throats now. A worse part to change IMO is the evaporator. Ask me how I know....

 

[gmcjetpilot]

Thermostat sure is tough, but for how long they generally last, how cheap the parts are, and that it is DIYable we can't complain. I'll take working on these cars any day over the crap they are forcing down our throats now. A worse part to change IMO is the evaporator. Ask me how I know....

I would not say it is easy, even though I did not do it, I researched. I would say the thermostat on my 69 Camaro with 350 V8 is easy. (10 mins). It took a full time mechanic in a shop 5 hours.... It was not the most experienced guy in shop but had been with a VW dealer and then Wolfsburg for 4-5 years. I guess that is the life of Mechanics... they win some lose some. Reminds me to swing by there with a gift card or cash for th mechanic. I felt bad. The dealer quoted $900.

As you know you have to pull the oil filter housing off to get to thermostat or OR make a special wrench.... The original Thermostat lasted 10 years. I am OK with that. I might DIY next time if there is a next time. I may still have the car in 10 yrs. It will only be 23 years old then.... I love it. It serves me so well for cross country travel, camping. I don't Daily Drive it... I have ( Gasp!!! ) a Nissan LEAF for putting around local. I have a BMW motorcycle for other long distance travel... Hard to beat the JSW TDI for utility, efficiency and gosh darn it it's fun to drive, handles well and the lovely low torque and cruise RPM in the low 2000's.... I only put 3000 to 4000 miles on it a year, most of it highway... and XC trips.

Anyway water temp in cool outside temperatures is now normal. I suspect it will be more efficient. I am considering upgrading the HPFP to the one from V6 when I do timing belt. Metal in the fuel system when HPRP hand grenades', injectors toasted would be very bad. Cost to fix would exceed value of car. The other thing is the Turbo... upgrade that...One of the two owners and mechanics at Wolfsburg discourages me from mods, says leave it alone. He's right. It is fine as is.... Although they do a lot of mods. They have a few Porsche and / or Audi in their shop almost every week for performance upgrades. There is also DPF delete and re-flash I might like to do.... that would improve economy.

 

[Nuje]

I guess that is the life of Mechanics... they win some lose some.

Given that most shops are charging in the $120-$150 range (and for SURE, the actual techs working on the car aren't paid anywhere close to that), it's not like the shop lost money there. The only money they did "lose" was in not having that tech working on another car for which someone was indeed paying $150/hr.
(*minus overhead, amortization of equipment, etc. etc. etc. of course).

 

[gmcjetpilot]

What are you talking about? You mean hourly rate? Yeah the shop made money, did not lose, but mechanic did work cheap that day... Jim and Pat, Wolfsburg owners are real car guys, mechanics, take care of employees... most of their mechanics have been there for 10 yrs or more.

Dealer lots of mechanic turnover. Awful service. Lucky to have an Independent VW Audi Porsche shop nearby. If it was the Dealer I'd do it myself, not only for cost but they would eff it up.

Dealer quote and others report the out of the door price for this job in $900 ball park.

I got a bargain... and a great job. My knuckles aren't bleeding and no grease under finger nails... blood pressure normal. Ha ha. Worth the $495.45. This is the first time I paid for something I could do... living the dream. It would have taken me 10 hours. I'm good but slow . I'd starve if I had to make living as Tech.

 

[Nuje]

Oh yeah - totally agree. Sometimes money spent is money well-spent; a person can get tired of "learning opportunities".