Temporary overheating! Scratching my head!

[qccoles]

02 A4 1.8t with 149k miles.

After my thermostat went out, it all went downhill...

First, overheated on the highway. Got the car towed back to my moms house which is in a different city.
Replaced the water pump and thermostat(it was the thermostat). Okay good, not overheating as bad as it was before.
Now, randomly, the car will overheat and immediately come back to normal. It can overheat slightly or it can start going into the last notch before it eventually goes back to normal operating temp. If it starts going too far i'll pull over and turn the car off for a little. This can happen at ANY speed....0 mph to 75 mph. I have bled and bled. I've ran the car with the lid off of the reservoir and kept topping it off, i've bled from the heater hose(immediately shot a stream of coolant a few feet into the air).

It was also beginning to have an issue holding idle while starting when cold. It wouldn't run rich as it should at cold start, it'd just start and fall flat on its face for about 10-15 attempts.
There was a DTC for G62(among 20 other codes), which was replaced a few months ago....so I replaced it again under warranty and this fixed the issue. I went ahead and replaced the other CTS also. I will post every code I pulled below. The only other problem I'm having is the brake lights staying on whenever the car is on, but will work correctly when the car is off. Replaced the brake light switch, same problem.



Scan: 01,02,03,08,09,15,16,17,26,36,37,45,46,55,56,63,76
-------------------------------------------------------------------------------
Address 01: Engine
Controller: 8E0 909 518 F
Component: 1.8L R4/5VT G 0003
Coding: 0016751
Shop #: WSC 63351
13 Faults Found:
16487 - Mass Air Flow Sensor (G70): Signal too High
P0103 - 001 - Upper Limit Exceeded
18057 - Powertrain Data Bus: Missing Message from ABS Controller
P1649 - 008 - Implausible Signal
17545 - Fuel Trim: Bank 1 (Add): System too Rich
P1137 - 002 - Lower Limit Exceeded
18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 002 - Lower Limit Exceeded - Intermittent
16955 - Brake Switch (F): Implausible Signal
P0571 - 008 - Implausible Signal
16501 - Engine Coolant Temp. Sensor (G62): Signal too Low
P0117 - 001 - Upper Limit Exceeded - Intermittent
16717 - Knock Sensor 2 (G66): Signal too High
P0333 - 001 - Upper Limit Exceeded - Intermittent
17072 - ECM Power Relay Load Circuit: (J271): Open
P0688 - 004 - No Signal/Communication - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - Upper Limit Exceeded - Intermittent
16686 - Cylinder 2 Misfire Detected
P0302 - 001 - Upper Limit Exceeded - Intermittent
17748 - Camshaft Position Sensor (G40) / Engine Speed Sensor (G28): Incor. Correlation
P1340 - 002 - Lower Limit Exceeded
17931 - Crash Signal from Airbag Controller: Implausible Signal
P1523 - 008 - Implausible Signal - Intermittent
18043 - Powertrain Data Bus: Missing Message from A/C Controller
P1635 - 008 - Implausible Signal - Intermittent
Readiness: 0000 1101
-------------------------------------------------------------------------------
Address 02: Auto Trans
Controller: 8E0 927 156 P
Component: AG5 01V 1.8l5VT USA 1213
Coding: 0001002
Shop #: WSC 03303
3 Faults Found:
18265 - Load Signal: Error Message from ECU
P1857 - 003 - Mechanical Failure
17087 - Brake Switch B Circuit Malfunction
P0703 - 003 - Mechanical Failure - Intermittent
18161 - Tiptronic Switch (F189): Implausible Signal
P1753 - 003 - Mechanical Failure - Intermittent
-------------------------------------------------------------------------------
Address 08: Auto HVAC
Controller: 8E0 820 043 Q
Component: A4 Klimaautomat 1015
Coding: 00000
Shop #: WSC 63351
4 Faults Found:
00787 - Temperature Sensor in Fresh Air intake duct (G89)
30-00 - Open or Short to B+
00604 - Potentiometer Positioning Motor for Air Flow Flap (G113)
30-10 - Open or Short to B+ - Intermittent
01592 - Air Quality Sensor (G238)
30-00 - Open or Short to B+
00819 - High Pressure Sensor (G65)
29-00 - Short to Ground
-------------------------------------------------------------------------------
Address 09: Cent. Elect.
Controller: 8E0 907 279 E
Component: int. Lastmodul USA 0305
Coding: 00003
Shop #: WSC 63351
2 Faults Found:
01496 - Bulb for Fog-Lamps: Left (L22)
57-00 - Electric Circuit Failure
00532 - Supply Voltage B+
53-10 - Supply Voltage Too Low - Intermittent
-------------------------------------------------------------------------------
Skipping Address 15-Airbags
-------------------------------------------------------------------------------
Address 16: Steering wheel
Controller: 8E0 953 549 L
Component: Lenksáulenmodul 0308
Coding: 01141
Shop #: WSC 63351
No fault code found.
-------------------------------------------------------------------------------
Address 17: Instruments
Controller: 8E0 920 950 H
Component: KOMBI+WEGFAHRS. RB4 D27
Coding: 03200
Shop #: WSC 03303
WAULC68E02A314135 AUZ6Z0B0125884
5 Faults Found:
00562 - Sensor for Oil Level/Temperature (G266)
30-00 - Open or Short to B+
00562 - Sensor for Oil Level/Temperature (G266)
29-00 - Short to Ground
00562 - Sensor for Oil Level/Temperature (G266)
27-10 - Implausible Signal - Intermittent
01316 - ABS Control Module
49-00 - No Communications
01320 - Control Module for Climatronic (J255)
49-10 - No Communications - Intermittent
-------------------------------------------------------------------------------
Address 45: Inter. Monitor
Controller: 8E0 951 177
Component: Innenraumueberw. 0604
Coding: 00001
Shop #: WSC 00000
No fault code found.

[G-Ride]

Wipe the dtc's and get a reasonable picture of which are accurate. You don't know how old any of those are.

What is the condition of the expansion tank and cap? I blew a head gasket a little while ago and had mild overheating issues. Everything in the cooling system was replaced with the exception of the expansion tank.

Once I changed that out and a new cap the cooling leak resolved and temps are stable.


Sent from my iPhone using Tapatalk

[ADCS]

Here are a bunch of random questions that come to mind...

What coolant are you using? What ratio are you mixing it to?
Is your coolant level dropping? Leaking or being ingested into the cylinders?
Are you getting heat out of all the vents when idling? How about at various rpms and engine loads?
Are the rad fans operating?
Have you bled air from the metal coolant pipe above the intake manifold?
When bleeding from the reservoir do you have the front end elevated? either by parking on an incline or using ramps/jack stands?
Is the system pressurizing?
Have you flushed the heater core?
What brand thermostat did you install?
When bleeding are you continuing to see bubbles?

Continuing to drive is not a good idea... you have probably blown the head gasket.

[csosnowski]

I would be more worried about P1340 - incorrect correlation, than the overheating at this point. ADCS is correct, you shouldn't drive the car until it gets figured out.

[qccoles]

Here are a bunch of random questions that come to mind...

What coolant are you using? What ratio are you mixing it to?
Is your coolant level dropping? Leaking or being ingested into the cylinders?
Are you getting heat out of all the vents when idling? How about at various rpms and engine loads?
Are the rad fans operating?
Have you bled air from the metal coolant pipe above the intake manifold?
When bleeding from the reservoir do you have the front end elevated? either by parking on an incline or using ramps/jack stands?
Is the system pressurizing?
Have you flushed the heater core?
What brand thermostat did you install?
When bleeding are you continuing to see bubbles?

Continuing to drive is not a good idea... you have probably blown the head gasket.

What coolant are you using? What ratio are you mixing it to? I haven't had the car for very long, but it had green prestone in it. I had to stick with prestone at the time my car broke down. I know I could've flushed and switched to g12 but all that was available was prestone at the time
Is your coolant level dropping? Leaking or being ingested into the cylinders? Not entirely sure just yet. I think it may be dropping, I'm going to have a closer look tomorrow.
Are you getting heat out of all the vents when idling? How about at various rpms and engine loads?I'd say heat is pretty random. It can be warm one minute and cold the next. Seemingly regardless of rpm's or speed.
Are the rad fans operating? They do operate.
Have you bled air from the metal coolant pipe above the intake manifold?I have not since the thermostat and waterpump were done. I was told by a friend that works at a local audi dealer that this wasn't a "real" way to bleed, I was told to bleed from the heater core hose instead.
When bleeding from the reservoir do you have the front end elevated? either by parking on an incline or using ramps/jack stands?I did not, I elevated the reservoir itself. Would elevating the car be more beneficial?
Is the system pressurizing?Yes it is pressurizing.
Have you flushed the heater core?I haven't.
What brand thermostat did you install?I don't recall the brand, but it was purchased from 1aauto.
When bleeding are you continuing to see bubbles?I don't remember but will take note once I attempt it again tomorrow. I do remember alot of glug glug glug.(for lack of better terminology)



I have not seen any thick smoke from my exhaust, nor i have seen any coolant in my oil or vice versa.

[diagnosticator]

If the coolant pump has a plastic impeller,(OE coolant pumps,) it is very likely the impeller has split/broken and is not gripping the pump shaft tightly. When this happens, the pump cannot pump the required volume of coolant and the engine will overheat, with the symptoms variable depending on if the impeller is turning with the shaft and how much slip there is if not 100%.

[qccoles]

If the coolant pump has a plastic impeller,(OE coolant pumps,) it is very likely the impeller has split/broken and is not gripping the pump shaft tightly. When this happens, the pump cannot pump the required volume of coolant and the engine will overheat, with the symptoms variable depending on if the impeller is turning with the shaft and how much slip there is if not 100%.

I replaced the water pump when I replaced the thermostat, little did I know that the current water pump was already metal and felt fine.

[1/4 scale]

check to make sure your fans are working (if not, either a fan problem or fan control module)

[qccoles]

Fans are working correctly. This problem can happen on the highway so I tend to shy away from it being fan related.

[ECS Tuning-Audi]

Likely you don't have the proper coolant level. Low coolant level will introduce air bubbles to the cooling system which form air pockets. When one of these pockets gets near the senor it shows it's over heating, once the pocket passes it will return back to normal temp.

Check for proper coolant level and be sure to bleed the system completely of any air.

Jason

[BARRY]

if you're ever questioning your cooling system replacing a 30 dollar water pump is good for safe measure. also do not use prestone...if you do make sure you do complete flush with water or cleaner. standard coolant mixed with G12 turns to sludge and will eventually clog up your heater core.

[qccoles]

Likely you don't have the proper coolant level. Low coolant level will introduce air bubbles to the cooling system which form air pockets. When one of these pockets gets near the senor it shows it's over heating, once the pocket passes it will return back to normal temp.

Check for proper coolant level and be sure to bleed the system completely of any air.

Jason

This makes alot of sense to me. I don't think it's possible for the engine to cool down as fast as it does if it were "really" overheating. I've tried a method or two of bleeding but doesn't seem to help, any suggestions? The heater core hose is pretty much a water fountain. The only time I've used the bleeder valve on top of the intake manifold was when I was getting coolant flow started after doing the water pump and thermostat.

[Let it snow]

Your overheating may be because of a bad head or gasket looking at your other thread.
http://www.audizine.com/forum/showth...turbo-manifold

[old guy]

Your overheating may be because of a bad head or gasket looking at your other thread.
http://www.audizine.com/forum/showth...turbo-manifold

Agreed. Sure sounds like a bad head/head gasket to me. Something probably warped when it overheated the first time and now you are dealing with it. Rough cold starts, random overheating on the highway are definite symptoms.

[qccoles]

Your overheating may be because of a bad head or gasket looking at your other thread.
http://www.audizine.com/forum/showth...turbo-manifold

Agreed. Sure sounds like a bad head/head gasket to me. Something probably warped when it overheated the first time and now you are dealing with it. Rough cold starts, random overheating on the highway are definite symptoms.

Really hoping it's just the gasket. I'm going to rip it apart and see like 20 bad valves and a warped/cracked head and god knows what else lol. Going to be a fire in my wallet.

[ECS Tuning-Audi]

This makes alot of sense to me. I don't think it's possible for the engine to cool down as fast as it does if it were "really" overheating. I've tried a method or two of bleeding but doesn't seem to help, any suggestions? The heater core hose is pretty much a water fountain. The only time I've used the bleeder valve on top of the intake manifold was when I was getting coolant flow started after doing the water pump and thermostat.

Sometimes you can get away with just using the bleeder valve on the top coolant pipe but if there air trapped deep in the system the only way to remove it completely is to use a purge air tool.



Jason

[qccoles]

Slight update. I had a cart ready with head gasket parts, but talked myself at giving a "liquid fix" a try. To my surprise, it worked. I did that, and threw in some new plugs for the hell of it. I drove the car for hours without any signs of overheating, and very nice heat the whole time. Very happy with those results.

Only problem is, my starting problem persists. The first morning after the liquid fix it started right up and idled correctly. A few hours later I started it and it had a very slight misfire for a second or two. It seems that the longer the car sits, the more severe the issue is. This morning, it still stalled on startup. It'll take a few tries to get it to start and hold idle. The accelerator does NOTHING while the car is attempting hold idle, so you can't try to gas it up to help it out.

If it matters, my EPC, ABS, and BRAKE(flashing) light are on.

[old guy]

Check your brake fluid level. That's probably why you have a flashing brake light.

The EPC and ABS both on are often associated with a dirty/defective MAF sensor. This could be part of the hard starting issue. So could a defective rear CTS (coolant temperature sensor).

I assume you have cleared all of your DTC's. Which ones have come back?

[viceprp]

I had a similar problem with my sister's B6 1.8T. She would have no heat on warm up but would see some when on the highway. Then the start ups weRe rough and then would idle out. Sometimes it would be 2 seconds. Other times it would take multiple start ups until it smoothed out.

I bought a used, bare head and swapped everything over to it. There was a hair line Crack in between cyl #3 exhaust valves.

What was happening was the Crack would expand when under load and would leak fluid when shut off. It would start filling cyl#3 with coolant.

[qccoles]

Check your brake fluid level. That's probably why you have a flashing brake light. My brake lights are on whenever the ignition is on, they do not go out. If the car is off, the brake lights work as they should, they come on when depressed. I bought a brake light switch to fix the issue but the problem persist. There are fault codes for the ABS module.

The EPC and ABS both on are often associated with a dirty/defective MAF sensor. This could be part of the hard starting issue. So could a defective rear CTS (coolant temperature sensor).

I assume you have cleared all of your DTC's. Which ones have come back?It's really funny you mention that, I just cleared the codes today, went for a drive, and scanned again. The MAF code came back. Along with a p1250, fuel level too low, which also points to the MAF if I'm correct. I was looking for a MAF sensor locally, and then got the notification from your post. I will post the new DTC's below.

Address 01: Engine
Controller: 8E0 909 518 F
Component: 1.8L R4/5VT G 0003
Coding: 0016751
Shop #: WSC 63351
7 Faults Found:
18057 - Powertrain Data Bus: Missing Message from ABS Controller
P1649 - 008 - Implausible Signal
17931 - Crash Signal from Airbag Controller: Implausible Signal
P1523 - 008 - Implausible Signal - Intermittent
16487 - Mass Air Flow Sensor (G70): Signal too High
P0103 - 001 - Upper Limit Exceeded
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - Upper Limit Exceeded
16687 - Cylinder 3 Misfire Detected
P0303 - 001 - Upper Limit Exceeded
17748 - Camshaft Position Sensor (G40) / Engine Speed Sensor (G28): Incor. Correlation
P1340 - 002 - Lower Limit Exceeded
17658 - Fuel Level too Low
P1250 - 008 - Implausible Signal
Readiness: 0000 1101

-------------------------------------------------------------------------------
Address 02: Auto Trans
Controller: 8E0 927 156 P
Component: AG5 01V 1.8l5VT USA 1213
Coding: 0001002
Shop #: WSC 03303
2 Faults Found:
17087 - Brake Switch B Circuit Malfunction
P0703 - 003 - Mechanical Failure
18265 - Load Signal: Error Message from ECU
P1857 - 003 - Mechanical Failure

-------------------------------------------------------------------------------
Address 08: Auto HVAC(I have not cleared these as of yet)
Controller: 8E0 820 043 Q
Component: A4 Klimaautomat 1015
Coding: 00000
Shop #: WSC 63351
6 Faults Found:
00787 - Temperature Sensor in Fresh Air intake duct (G89)
30-00 - Open or Short to B+
01841 - Potentiometer/Actuator for Temperature Flap: Left (G220)
30-10 - Open or Short to B+ - Intermittent
01810 - Actuating Motor for Temperature Flap: Right (V159)
41-10 - Blocked or No Voltage - Intermittent
00604 - Potentiometer Positioning Motor for Air Flow Flap (G113)
30-10 - Open or Short to B+ - Intermittent
01592 - Air Quality Sensor (G238)
30-00 - Open or Short to B+
00819 - High Pressure Sensor (G65)
29-00 - Short to Ground

-------------------------------------------------------------------------------
Address 09: Cent. Elect.
Controller: 8E0 907 279 E
Component: int. Lastmodul USA 0305
Coding: 00003
Shop #: WSC 63351
1 Fault Found:
01496 - Bulb for Fog-Lamps: Left (L22)
57-00 - Electric Circuit Failure

-------------------------------------------------------------------------------
Skipping Address 15-Airbags

-------------------------------------------------------------------------------
Address 16: Steering wheel
Controller: 8E0 953 549 L
Component: Lenksáulenmodul 0308
Coding: 01141
Shop #: WSC 63351
No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments
Controller: 8E0 920 950 H
Component: KOMBI+WEGFAHRS. RB4 D27
Coding: 03200
Shop #: WSC 03303
WAULC68E02A314135 AUZ6Z0B0125884
3 Faults Found:
00562 - Sensor for Oil Level/Temperature (G266)
30-00 - Open or Short to B+
00562 - Sensor for Oil Level/Temperature (G266)
27-00 - Implausible Signal
01316 - ABS Control Module
49-00 - No Communications

-------------------------------------------------------------------------------
Address 45: Inter. Monitor
Controller: 8E0 951 177
Component: Innenraumueberw. 0604
Coding: 00001
Shop #: WSC 00000
No fault code found.

[old guy]

The 16487 obviously indicates a problem with your MAF sensor. Can you monitor your MAF readings? What are you getting on a cold start at idle and what are you getting at idle once warmed up? What are you getting at WOT around 5,800 rpm?

The MAF issue could also be what's causing the misfire and hard start issues.

The 17658 is a an informational code. It is only stored in conjunction with misfires or malfunctions concerning the O2 sensor control if too little fuel is or was in the tank at the time. Again, this could be related to the MAF sensor issue.

[qccoles]

Put a new MAF in today. Still misfiring pretty bad on cold start. No cigar.

[diagnosticator]

If you run the HVAC servo motor adaptation, doing that often resolves the "Blocked or No Voltage" DTCs stored in the controller and can restore normal operation for awhile at least. Worth a try,.

[qccoles]

Another thing I've noticed is that the misfire is steady. It misses evenly, as if it were running on 3 cylinders. The DTC says cylinder 3 misfire. I believe the previous owner installed 2.0 coils on the car. Could a bad coil cause a misfire ONLY for about 30 seconds after a cold start?

Also, maybe 20% of the time, the car will start right up on a cold start with zero misfires or hesitation.

[BARRY]

if you're getting misfire, swap the ignition coil to another cylinder. if it misses on that cylinder then the coil is faulty. if it does not inspect your ignition coil wiring harness as it could be grounding out due to a break in the insulation.

[old guy]

Put a new MAF in today. Still misfiring pretty bad on cold start. No cigar.

Have you reset all your DTC's? If so, which ones come back?

Another thing I've noticed is that the misfire is steady. It misses evenly, as if it were running on 3 cylinders. The DTC says cylinder 3 misfire. I believe the previous owner installed 2.0 coils on the car. Could a bad coil cause a misfire ONLY for about 30 seconds after a cold start?

Also, maybe 20% of the time, the car will start right up on a cold start with zero misfires or hesitation.

I second Barry's recommendation. Try swapping coils and see if anything changes. Unfortunately another possibility is a small coolant leak into cylinder three. Thus the hard start misfires on one particular cylinder and then it clears up after the engine is up and running. One thing you can do is to remove all the plugs and rotate the engine by hand so you can see the top of all four pistons. If piston #3 looks considerably cleaner it would be a pretty good indication of a coolant leak. You should be able to get a decent view of each piston once at TDC.