Over cooling Issue

[zolorin]

Hello all, this is my first time asking a question on this forum, so don't be too rough on me. I had been reading whole bunch of this forum for many problems in the past but now I am dumbfounded.

Ok, I have bought a 2000 VW Jetta TDI with 5 speed about a year ago. The PO have told me that he have installed a new clutch from the VR6, had replaced a turbo (gave me an old one) and told me that he can't keep his car because it was in a wreck and his insurance would not insure it with a salvage title. Price was right, I bought the car replaced the bumped, fender and a headlight and finally started to enjoy the mpgs (up to 54 on the highway). Resolved the check engine light with the glow plugs/harness kit and the car was very happy. So over the x-mas brake, 20K miles later, I have replaced the timing belt, water pump, cam followers, vacuum and fuel hoses, the 200K deluxe kit from boraparts.com This is not my first time dealing with the TDI since I have helped a buddy to rebuild an engine 4 years ago. All went well, all hoses, belts, accessories, and skin on my hands had been replaced. I have decided to change the thermostat as well -- just hate to have my investment to go up in smoke over a 20$ part. (which is an outrage since I am used to thermostat being $5). Anyway the TDI thermostat from wheler (spelling is off) did not fit and the PO had the single action thermostat from the 2.0L installed. So I have replaced with the identical looking one.

So initially everything looked fine however on the long drive to work a month later my car started to over cool (as the gauge would go below the 190 mark on the downhills). This is happening in south cal, no snow, just maybe a bit extra wind. So I was perplexed. A week later the over cooling issue exacerbated that my water temp rising to normal operation range went down to fully cold (fully left) and stayed there. Once I pulled over I touched the hoses and they were bone cold.
So two weeks ago I have replaced the 2.0L thermostat to a real TDI from wheler and the problem still persists. Now the temperatures are low almost all the time. I did notice that the lower plastic pan had several screws out and the radiator may be getting additional cooling because there is an easy way for hot air to escape.

I have replaced the water pump, and two thermostats and 6L of fluids and the engine is way way too cold.

a. is this normal?
b. is this because of the lower pan being not fully secured
c. is my egr being not as good -- it had been weeping some oil lately
d. my water pump running backwards
e. I am dreaming and I need to wake up from this nightmare

Thank you all

 

[Seatman]

Well what I can say is that my cover's missing from underneath and my car still gets hot even in -15c. I think it's possible it's something to do with the thermostat as the one that was in it sounds like the wrong one and the one you fitted was the same as the one you took out. Maybe they don't work in the 1.9 tdi.

 

[zolorin]

replaced the thermostat with a dual action tdi thermostat after the issue started -- did not solve the issue. This thermostat is a german made (not VW) but one of the german companies.

the lower engine cover lost one or two bolts so it flaps in the air, but it is installed -- I will tighten it up tonight.

the temps are 5-15C here (above freezing) (40-60 F)

 

[andreigbs]

You possibly have air in the system, needs to be burped out.

Did the new T-stat have the tabs?

An OEM t-stat is around $40, how much was your replacement?

 

[oilhammer]

I would only use an OEM thermostat from the dealer (usually about $45). However, I do not think that is your problem, more likely your coolant temp sensor is flakey.

OBD works, start there and see if any DTCs are stored in the engine or instruments.

 

[zolorin]

replacement was 20$ and it was not VW part.

Temp sensor could be an issue but the coolant hoses were bone cold (normally touching 160-190 hoses is "fun"). Radiator is also very very cold (few degrees above OAT).

Now for burping the system, how would you recommend doing that -- there is no radiator cap on it. How does one do that?

As far as tabs are you talking about the ones inside the outlet flange?
as seen in the picture?
http://forums.tdiclub.com/showthread.php?t=148452&highlight=thermostat+replacement-tip

Thank you a great deal

 

[oilhammer]

There is not really any issue with getting the air out of the system on that car, it will purge itself, that is what the small bleed hose coming from the top of the cylinder head over to the coolant bottle is for.

Keep in mind, that engine really will not get 'hot' that quickly without driving it, and even then it can not ever really get hot enough to need the cooling fans to run on all but the hottest days (and on those days, you'd most likely be running the A/C anyways).

 

[zolorin]

so it has purged, I replaced one thermostat, drove 5,000 miles as this started to develop, change a thermostat and then drove another 1,000 miles, I do a lot of driving for work

so of to OEM VW part, which was 52$ at my stealer

 

[Seatman]

I didn't have any problem with an after market thermostat, my car's still hot but I just can't see what else would cause your car to stay cold. The thermostat stays shut, the coolant heats up to a certain point, the thermostat opens to allow the hot coolant to go to the radiator for cooling and so on and if it was in the wrong way round I would expect the car to over heat so I can only think you must have a duff one. You could try putting it in a pan of water with a thermometer and warm the water until the thermostat opens, if it open immediately or is already open then that would confirm it and save you spending $52 at the stealers. Just let it heat to 70-80 degrees but be careful not to boil it.

 

[Dimitri16V]

well , if the gauge drops from the middle to cold in short time , it is the sensor.

try adding more coolant , instead of water

 

[Seatman]

" A week later the over cooling issue exacerbated that my water temp rising to normal operation range went down to fully cold (fully left) and stayed there. Once I pulled over I touched the hoses and they were bone cold."

 

[Deezlfam]

Sorry to bring back a pretty old post here but I was reading this and just recently my 98 started doing this same thing. Started out on a trip at night it was seriously overcooling like on the 160 on the freeway doing 60mph with not much load. It then would go to the last cold line on a downhill section. It was probably 60* outside. I pulled over and checked everything out and it seemed fine. After pulling over I noticed that the temp went back to the middle mark but once I drove it again it would seriously cool down. Well today i'm driving along after just getting on the freeway and the check engine light came on. It was about 70* all day today and in mixed city highway driving it was anywhere from the middle mark to 160*. I have already replaced a coolant temp sensor that made the glow plugs work again. I am assuming my other one may have failed or my thermostat? I will try to get the light checked out tomorrow but its labor day so I dunno. Any help would be great!

I see this is in the mk4 section... I do have a mk3. Sorry googled the issue.

 

[vwdieseling]

Your thermostat might be stuck open. Did you check your resevoir coolant level. If it is really low your thermstat is stuck open. You can pinch your radiator hoses as well. If they pinch and coolant flows back and forth through them this means the stats open. If it is open coolant will surge through the system into the resovoir bowl. Not all stats are precise, but let the engine cool down to ambient air temp lets say overnight. Start the engine and let it warm up a little for about 8 or 9 minutes then pinch the hose. The thermostat should be closed at this point, if its open as stated before coolant will surge through the hoses when pinched indicating stat failure. If the radiator hoses have pressure and as example bulging and cannot be pinched and you don't have flow it is closed. (It is probably time to replace the stat.) Try Behr stat 189 F for TDI they are OEM and run about $15.00 to $34.00.

 

[Deezlfam]

I also read that it could just be the Coolant temp sensor reading incorrectly. I wish I had an infrared temp reader. I will try the squeeze trick. But at this point I am wanting to replace the other temp sensor I haven't already replaced and my t-stat and probably do a cooling flush while I am at it. Would a stuck open t-stat trigger a CEL somehow? Where is the T-stat located?

 

[vwdieseling]

The stat flange is in the front of the engine block it is plastic with two 10 mm combination torxs fastners that hold the flange in. The upper radiator hose connects to it. The stat seats into the block. If or when you remove the flange make sure your coolant is drained or it will run out when you loosen the flange fastners. I recommend removing the hose first. A stuby handled ratchet and short extension is nice because it is tight in this area along with 10mm socket. I would replace O ring flange gasket as well. I don't like flushing unless really needed. The reason is the shelf brands like Prestone and others have certain agents that can actually damage gaskets. There are cases when flushing is neccessary especially if there is a restriction in the system. I recommend a good stat like Behr or Stant made for the 1.9 TDI with proper temp range. Behr being the better choice. I don't recommand a Motor Rad stat these are expensive and in my opinion junk. They are sold by AutoZone and Advance Auto. I've had problems in the past with these stats they are fail safe and stick open. I've never seen a CEL thrown for the problem your descriping. You need to have a scan done to determine that. Good luck. It could be your sensor signal is off, but it could actually be running below temp. It's overheating that causes problems, and I have been dealing with that with my TDI. Mine has been hitting 101 C, but on a cool day around 80F it is fine. Also 101C at stops only once air flow starts through radiator temp drops to normal.

 

[Deezlfam]

I can't seem to find any stores that carry a stant or Behr T-stat. Would a stealership part be just fine? Edit... As another note when i shut down the car and fired it back up again the CEL was out. There was no difference in drivability or noise etc. Autozone was open and I had the CEL pulled it is actually a Air/Fuel metering code P1248.

 

[vwdieseling]

I can't seem to find any stores that carry a stant or Behr T-stat. Would a stealership part be just fine? Edit... As another note when i shut down the car and fired it back up again the CEL was out. There was no difference in drivability or noise etc. Autozone was open and I had the CEL pulled it is actually a Air/Fuel metering code P1248.

P 1248 code is start of injection deviation, this is pump related. Related problems, Solutions

• Loss of Power at high Engine Speeds
• Engine difficult to Start

[edit]
Possible Causes

• Start of Injection Timing Regulation not OK
• Injection Pump Control Range blocked/dirty (e.g. by Metal Particles)
• Engine has stalled / ran out of Fuel recently
• Wiring/Connectors from/to Injection Valve (N108) faulty

[edit]
Possible Solutions

• Check/Adjust Injection Start
• Check Fuel Supply
• Check/Replace Fuse(s)
• Check/Repair Wiring/Connectors from/to Injection Valve (N108)

This above information is from Ross Tech website. The thermostat you can order on line from Autohauz or Volkswagen Parts Place, be sure to get the flange gasket.
Try this link to get an idea to whats going on.
http://pics.tdiclub.com/data/500/N108.pdf

 

[Deezlfam]

Yay what a bucket of fun... Well it hasn't run out of fuel recently, nor has it stalled. There is no loss of power at high rpm and it is no different starting it. We run the same fuel we always do... I have replaced the fuel filter regularly and lube my IP with Diesel Kleen. This is all beyond something I want to mess with so I think I am going to take it in to my local vw guru. Didn't need to spend the money on this right now.

 

[vwdieseling]

I hope you get it worked out, I understand. I just dumped about 1000.00 in mine for injectors and EGR valve. My pump got high miles on it too.

 

[Deezlfam]

Took it to the shop they told me the code I got at autozone wasn't what pulled up on there computer. That it was for injection pump timing at start up off or something. They then asked me if I had my timing belt replaced recently and I did by them so they told me they would adjust it for free. So we will see...

 

[vwdieseling]

Great at least the major problem is solved, good luck with the stat problem.

 

[Deezlfam]

Well they checked the timing today and it was not off... They did do some very small timing adjustment or something to see if it would help but it didn't. The T-stat was bad so that problem is fixed. Heats up at op temp just fine now. But what could this cold start code be all about? They didn't tell me what the code # was just cold start timing off or something like that. Having trouble researching that one...

 

[vwdieseling]

Well they checked the timing today and it was not off... They did do some very small timing adjustment or something to see if it would help but it didn't. The T-stat was bad so that problem is fixed. Heats up at op temp just fine now. But what could this cold start code be all about? They didn't tell me what the code # was just cold start timing off or something like that. Having trouble researching that one...

Is it still throwing the code? If it's not maybe a fluke one timer Your cold start injector is not working properly. The injector is in the pump. It can be replaced, but you have to remove the pump. I don't know where you could even get one. Possibly a used pump where the injector is still good. The old 1.6 diesels had a cold start cable and a manually actuated valve, the newer 1.9 TDI's have the cold start injector that modifies the diesel at the start of injection until 2200 RPMs. The link in one of my posts above, I posted has a diagram of it. It's N 108, VWAIRCOOL did tutorial with picks on how to replace it.

 

[Deezlfam]

It came back but it still runs just fine so idk? What should I do... Don't really have the money for a rebuilt pump. What is going to happen if I just keep driving it? I read around that it usually has something to do with someone replacing the timing belt. And I did just have that done so I don't know what to think about that. It has run perfectly fine for several thousand miles since then...

 

[vwdieseling]

I really can't answer on that because it's your decision. It's your car. I undrstand money issues, I've got a ton of those. It's your peace of mind. The pump could fail or it might not. If it fails you will be stuck. Try (Diesel Purging) it, I mean real Diesel Purge. and check the wiring from cold start injector and clean the contacts on the pump harness pigtail with contact cleaner. Try to clear the CEL. A good rebuilt pump is about a thousand dollars. This is the best that I can help you.

 

[Peds2008]

Egr thermostat is the issue for over cooling!!

 

[muzy]

Egr thermostat is the issue for over cooling!!

First for me to hear of egr thermostat . Did a quick search , no good results.
Please add picture or part number.
Cheers

 

[wonneber]

^^ Location Yorkshire
Europe thing??
Plus 3.0 tdi

 

[Nich]

I had a bad mechanice replace my alternator and forgot to reconnect the Turbo to the vacuum lines. Top speed was about 75 mph and the engine never really warmed up. Probably not your issue but just in case your out of ideas to check