I have an AWM enegine. Is that what you have? Nice touch BTW!

 

Yes, that's an AWM. The CTS at the bottom is actually a dual thermal switch for the fan.

OP, please don't buy Fram Filters. Baby Jesus is sitting next to me bawling his eyes out. oke: You can buy stock filters on line for $5 and change.


edit: Oh, and nice write up! :thumbup:

 

I find it easier to drain the radiator using the drain valve than pulling the fan switch. The clip on the switch can be difficult to seat properly sometimes.

You contradict yourself on the O-ring. Make sure the thermostat goes in before the O ring. I also clean the housing with some fine grit sandpaper to get the rust out for a better seal.

You can also use a 10mm socket on a swivel extension to loosen and tighten the bolts. The allen socket can strip if the bolts are stuck.

 

Great additions to the write up. I would of messed up the Oring.

 

Sorry to revive an old thread guys. Should any sort of grease or anything be used on the o-ring to help it seal? I was told by someone to do so to prevent leaks, but have not been able to find any sort of backup evidence on the site.

 

anyone? i plan to do this monday on my day off

 

No grease or sealant needed.

 

thank you sir, will take your advise

 

Think it's possible to skip the draining of the coolant and simply quickly replace the thermostat? Thought I read somewhere that a chip tuner was doing that in-house as their ECU upgrade required a different t-stat.

Any downside to this? Would air get in? I would imagine it wouldn't, and then I would only need to catch whatever leaked out while switching the thermostats and refilling the reservoir to the proper level with new coolant.

 

There is no quick replacement of the thermostat unless you remove the alternator. You will leak a good amount of coolant and let air in the system.

An colder thermostat is not needed, but there may be a tuner who suggests it.

 

Thanks for the info PZ! I and a lot of member appreciate your experience and helpfulness!

 

I got the generic engine warning light this week on my 04 passat. Dealer says I have both a bad thermostat and a bad temp sensor ($450 fix). Seems odd that the thermostat is bad at the same time that the sensor that is supposed to tell me that the thermostat is bad is bad too. Car's a 1.8T 4motion wagon with about maybe 80K miles.

Does anyone have experience with what the PO said re: "...a P2181 code. Did my CTS (coolant Temp sensor) first and now moved on to this hoping it will fix it."?

Thanks in advance!

 

There have been a couple of cases like that. The CTS may or may not have been bad, but the thermostat fails slightly open and the car reaches operating temp a little too slowly, setting the code.

$450 is pretty high for this work. At 80K you are also due for a timing belt change that would normally include a new thermostat. You are a bit too far, but I would do the whole timing belt job (and CTS) for $180 labor and you supplying the parts (about $260 at www.ecstuning.com).

 

Thanks PZ. I had the dealer change the thermostat, figuring I was already in for a diagnostics charge and I could do the temp sensor if I needed to. They were sure the thermostat was sticking. Seems like all's okay now.

I've got a good mechanic for the timing belt. It's on the list.

 

So far so good on the thermostat-only change (no temp sensor change) keeping the engine light off. Four months later all seems well. Well almost well. Either the new thermostat is leaking or the water pump is on its way out.

Looks like it's time for the whole timing belt, water pump and while-you're-in-there service.

 

You don't want to drive with a leaking water pump too long. I had someone drive their car to my house to check a coolant leak. He had to stop on the way to fill up the coolant (less than 10 mile drive). Once I got it apart, I found the water pump seized and had started to strip a 1/4" section of the timing belt.

 

Great writeup! I saw elsewhere that ppl were saying you have to remove the alternator for the thermostat, which I was not looking forward to...

I'll be doing this while doin my TB. And to clarify, do I put the thermostat back in, then put the O-ring in the housing, then re-attach housing? That correct?

 

I have the P2181 code and replacing the sensor didn't help. I thought it did but its gotten worse since. My thread is here:
(P2181) Coolant Sensor Replacement - 2003 Passat Wagon 1.8T AWM

I have some questions here because I'm thinking about doing the thermostat replacement described in this thread.

I notice in this tutorial you have the CTS located on the lower radiator hose. Does that mean there's a second CTS in my Passat? I thought there was just the one behind the engine (see my thread for pics).

I've read the comments and I'm trying to figure out when the thermostat o-ring should go on. We want the o-ring to go in first or the thermostat to go in first?

Can someone post pics of the drain valve for the radiator so I know where to drain?

I remember doing a thermostat change on a Hyundai once and it was a PITA because air gets into the system. I remember having to squeeze the hoses to work out an air pocket where the thermostat was. How do you deal with that on a Passat? Does it automatically purge the air? Can you discuss more about how you go about reintroducing the coolant?

If we're draining the coolant wouldn't we be better off just buying fresh coolant? We're at 90k mi.

Thank you for your time

 

I have the P2181 code and replacing the sensor didn't help. I thought it did but its gotten worse since. My thread is here:
(P2181) Coolant Sensor Replacement - 2003 Passat Wagon 1.8T AWM

I have some questions here because I'm thinking about doing the thermostat replacement described in this thread.

I notice in this tutorial you have the CTS located on the lower radiator hose. Does that mean there's a second CTS in my Passat? I thought there was just the one behind the engine (see my thread for pics).

Yes there are 2 different temperature senders. The one at the bottom of the radiator (i believe) controls the radiator fans.

I've read the comments and I'm trying to figure out when the thermostat o-ring should go on. We want the o-ring to go in first or the thermostat to go in first?

Thermostat first with the little bleed hole towards the top, then the o-ring.

Can someone post pics of the drain valve for the radiator so I know where to drain?

There is a drain valve (red) behind the driver side fog lamp grill. You'll have to remove that grill and pull the intercooler "ducting" out of the way a bit. There is a fitting you can slide a 1/2" hose on so you don't spill any.

I remember doing a thermostat change on a Hyundai once and it was a PITA because air gets into the system. I remember having to squeeze the hoses to work out an air pocket where the thermostat was. How do you deal with that on a Passat? Does it automatically purge the air? Can you discuss more about how you go about reintroducing the coolant?

You have to pull back the heater core hose (the one with the hole) until the hole is off the end of the heater core line. Don't completely remove the hose. Raise the coolant tank a bit(so it's higher than the heater hoses) then fill the tank until a smooth stream of coolant runs out of the bleeder hole on the heater core hose. Once no more bubbles come out, slide the hose all the way back on and put the hose clamp back on. Lower the expansion tank (don't forget to re-connect the coolant level sensor connector). Run the engine until it's up to operating temp, and top up with coolant if necessary.

If we're draining the coolant wouldn't we be better off just buying fresh coolant? We're at 90k mi.

That would be a good idea.

Thank you for your time

No problem.

 

To fill the coolant and evacuate the air, you need to back off one of the heater core hoses. It is marked, and there's a hole in it. Slide it off the fitting until the hole is open. Then unscrew the top off the resivoir, take out the three mounting screws, and hang it so it's higher than the heater hoses.

All this allows the air to escape as you refill the coolant.

 

Nice. Now where's the diy for the 2.8? Link please.

 

LOL, I thought you already knew how to do it?

A6 & Passat
1. Inspect coolant lines for bleed screws. One is located at front of engine near the upper hose
connection. Loosen bleed screws front and on rear coolant pipe.
2. Expose vent hole on heater pipe at firewall connection by pulling back heater hose. See Fig. 3 . Fill
cooling system through expansion tank until coolant comes out of vent hole and bleed screws. Tighten
heater hose and bleed screws.
3. Fill expansion tank to proper level. Install expansion tank cap. Adjust heater controls to maximum
heat position. Start engine and raise engine speed to 2000 RPM for about 3 minutes. Ensure cooling
fan operates. Return engine to idle. Check coolant level in expansion tank. Fill as necessary. Repeat
and recheck.

Here's a link to the PDF manual: http://vwts.ru/engine/aha_atq/aha_atq_repair.zip

 

Why do you have to remove the clip holding the the CTS on the lower radiator hose. Remove the CTS and drain the coolant into a bucket . Why can't you just go straight to removing the intake hose and going from there?

 

you'd be leaking coolant everywhere when you removed the thermostat housing if you don't drain the system first.

 

Alright, that makes sense. Thanks.

 

Alright I think I'm ready to attempt this replacement if the weather is good this weekend. I took a look at that manual but I still don't understand where the hose with the bleed hole is on the 2003 Passat 1.8T AWM. Can someone point out where the hose? Here's a pic from under my hood:

I did manage to find the drain valve with the pic posted by woodardhsd. On mine it is on the driver side lower grill. The plastic piece of the grill pops off. Then there is a rubber sheet. I had to pull the rubber sheet to the side and then I was able to see the red valve thing. Here's a pic:

Am I to understand that if I drain via the drain valve that I don't have to remove the lower CTS? I did try to find the CTS but I had trouble. Here is what I think might be it, off the left side of this tube.

Also, I'm going to flush the coolant system. Maybe the coolant mixture is wrong. Also I have 90k miles on the car so I figure why not just change the coolant (as was suggested here as well). From what I've read the Passat 1.8T AWM takes 7 liters of coolant. They sell the coolant full strength and it must be diluted to recommended half coolant (3.5L), half water(3.5L). 1gal of coolant is 3.7 liters, so I bought a gallon for $25 from VW.
Here's are some good coolant related threads
taligentx.com: Passat - Coolant Flush
How much distilled water needed for coolant????
Just had Coolant replace with g12... They didnt mix water.... Problem???

I don't expect to get a 50/50 exact mix. There will always be some water left in the system I'd guess. One interesting thing in that taligentx post is he loosened the drain nut on the water pump as well to really get everything out. I may or may not do that I don't know yet.

I bought my thermostat and o-ring already. The confusing thing is there are two different temps these thermostats are usually stocked at for Passats. I made sure to get the default.
Fitment Notes: 190f/88c Thermostat, MFG RECOMMENDED TEMP - OE TYPE - 190 DEG
Amazon.com: Motorad 475-190 Thermostat: Automotive $10.17
I couldn't find the gasket on Amazon so I got it from Autozone: Felpro/Thermostat Gasket $1.69
The gasket looks barely to be the radius of the thermostat but autozone says it's the right part. Also I have shoprunner so I get free ship at autozone for some things if anyone who's a contributor here needs it.

 

Alright I think I'm ready to attempt this replacement if the weather is good this weekend. I took a look at that manual but I still don't understand where the hose with the bleed hole is on the 2003 Passat 1.8T AWM. Can someone point out where the hose? Here's a pic from under my hood:
View attachment 3837

I did manage to find the drain valve with the pic posted by woodardhsd. On mine it is on the driver side lower grill. The plastic piece of the grill pops off. Then there is a rubber sheet. I had to pull the rubber sheet to the side and then I was able to see the red valve thing. Here's a pic:
View attachment 3838

Am I to understand that if I drain via the drain valve that I don't have to remove the lower CTS? I did try to find the CTS but I had trouble. Here is what I think might be it, off the left side of this tube.
View attachment 3839

That drain valve is where i drained my coolant from when i was doing the thermostat. Just attach a simple rubber pipe to the outlet and drain it to the container by opening the valve.

However when you are changing the thermostat, some coolant will still spill out of the thermostat area. Just make sure you have some rag to collect it.

Remember to fill it up with the bleeder hole venting, otherwise you will have air pockets. The bleeder hole is in one of the pipes with white circle in the battery area. Hope this helps.

 

U r correct about the drain valve. No need to pull cts. The drain valve is definitely the best way to drain the system IMO. Or at least it is the easiest, i doubt it gets everything out...

You may be able to find my thread when i did this this winter there might be some extra information you could find useful. I am going to add that on my car there is an intake manifold support bar that really makes it a PITA to get your hand in there and you have to work around it. It is possible to do, since i did it, but if i had to do it again i would remove it. I would also remove the throttle body, four 5mm allen screws, which gives you even better access and allows you to easily remove the intake manifold support bracket. Have an extra throttle body gasket on hand just in case ($5).

 

Thanks to everyone for their help. I drained the coolant, replaced the thermostat and added new coolant. The experience was mostly like it says in this thread.

The first thing I did was drain the coolant. I popped off that plastic grille (facing the car it was on the bottom right side (driver's side). No tools required, it just pops off. After that I had to pull back a rubber flap which was covering the grille (I posted a pic of it earlier).

I did not have the right hose initially and I couldn't find a good way to drain without the hose so I went to Home Depot and bought a clear plastic hose with 1/2 ID. It was only a few dollars and worth having the right size because it fits on properly.

My 1.8T has a coolant capacity of about 7 liters (FYI - B5.5 Fluid Capacities) so I expected that when I drained I would get that (almost 2 gal) but I didn't even get close. I got less than a gallon. The coolant reservoir was normal before I started so I don't know if they mean absolutely full capacity or it just doesn't drain everything or what. I did look for that place under the car where apparently there is a nut on the water pump where you can do additional draining but I didn't find it (I wasn't even sure where the water pump was).

Once the system was as drained as it was going to get, I poured in a gallon of distilled water (I purchased several at cvs for a few dollars) and let it drain right out. The water came out slightly orange tinted but was mostly clear. Then once that drained I made sure to retighten that red screw. Not too tight to strip it but tight. I used two empty windshield washer jugs to store the what I drained. I have to recycle it but I don't know where (autozone wouldn't take it). FYI coolant is poison and dogs love the taste of it (it's sweet I think) so seal it immediately, don't just leave an open tub of what you drained around or your dog or other animals could die.

Getting the thermostat out was difficult and I didn't take pictures. It all comes down to having the right tools. I had tried a hex attachment to my socket wrench but it only worked on the top screw and on the bottom one I totally stripped the female hex part of the screw, because of the angle and I think it was stuck. Luckily I could also just use a regular socket attachment since the screw has a male hex part.

Someone told me to feel the water pump but I didn't feel anything when I stuck my finger in the thermostat hole. So I just replaced the thermostat. I had trouble keeping the o ring in place and then getting that cover piece back into place. No good advice here just have a lot of patience. I dropped the screws several times. If that happens you'll have to remove that plastic cover piece under the car to get them. Since I was also changing the oil that wasn't a problem. Also I probably tightened the screws much more than I should have. I went super tight but I probably should've just gone a quarter turn past resistance.

To get at the air relief valve in the coolant hose I took off that plastic cover to the battery, then broke the seam on that weather stripping to take off that entire plastic piece surrounding the battery. The hoses were to the right of the battery and covered in some corrugated plastic that took me a long time to stretch back. I think what happened is the protective plastic piece that covers the hoses was stuck on the hose clamps when I tried to move it back. Also there was a plastic zip tie holding the plastic around the hose so I cut that. Here's a picture. I inched the left hose with the hole off just enough to uncover the hole but not so much that the hose was disconnected.

I put some paper towel I put around the hose to catch any coolant:

Next I went to refill with the coolant and distilled water (50/50 mix). I unscrewed the coolant reservoir and under it there was a electronic cable that was plugged into the reservoir, which I'm sure was some sort of sensor. I disconnected that so that I could lift the reservoir higher. The reservoir needs to be as high as possible when you pour the coolant in so that the air will be forced out. I wasn't able to get it that high because the connecting hoses were pretty short.

I got a big clear empty bottle and filled it up half coolant and half distilled water. I poured it into the reservoir and then I did that over and over again. I would occasionally hear bubbles and air escaping. Eventually after some time I saw a stream of coolant shoot out of the air relief valve and I was done. I pushed in that hose all the way and put back the spring clamp, and then I put the cap on the reservoir, reconnected that cable to under it and refastened it.

My CEL has not come on due to P2181 since. It's either the thermostat replacement or the proper ratio of coolant to water that the system finds within normal range. Immediately after I did have an odd P0456 which indicates a small leak in the EVAP system but I cleared it and it hasn't been back. So finally I was able to drive 200 miles without a CEL and take my car in for NYS inspection (it passed).