Overheating Help!

[TrillA4]

TL;DR cars overheating i changed the thermostat and bled system of air problem remains. Specs 2001 a4q 1.8t k04 tt injectors and maf housing giac tune, waterpump done 20k miles ago. Have some new cel codes need help.
Over the past few months my car has been losing coolant little by little every so often, i usually would check it and top it up regularly (With water) or the low coolant light would come on and i wold fill it that day (with water). Not sure where i was losing coolant from figured maybe my k04 was burning some off. So last thursday i'm driving to school and i notice the low coolant light, it may have come on few days before and i had forgotten about it but i cant be sure anyway it was really low nothing in the overflow tank. The car starts running hot so i pull over and wait for it to cool a bit so i could add water. I drive a few minutes it starts running hot again i pull over on i78, let it cool for a longer time and add any water i had in my car , after that ran okay temp wise and i got to school.

After school drive home runs hot again go to walmart buy more water fill tank still running hot the rest of the way home. over the weekend i bled the system it still ran hot so i changed the thermostat and now its still running hot with new vemo thermostat and bled system of air.

Top rad hose hot bottom one not so much , car cools to reg temp if i let it idle long enough or have heat on full and idle, i do have vagcom free version but not very experienced with it, i noticed i have some new codes here they are
(i also had some misfire codes before i cleared them, ive had those for a few months i figured it was a bad coilpack)

6 Faults Found:
17734 - Knock-Control: Cylinder 2: Regulation Limit Exceeded
P1326 - 35-00 - -
16712 - Shareware Version. To Decode all DTCs
P0328 - 35-10 - P0328 Knock Sensor Circuit High Input

16795 - Shareware Version. To Decode all DTCs
P0411 - 35-00 - Please Register/Activate
16804 - Catalyst System; Bank 1: Efficiency Below Threshold
P0420 - 35-00 - -
17735 - Shareware Version. To Decode all DTCs
P1327 - 35-00 - Cylinder 3 Knock Control Limit Attained

17736 - Shareware Version. To Decode all DTCs
P1328 - 35-00 - Knock control, cylinder 4 - control limit reached

Any help or ideas would be appreciated

Thanks,
ROB

[Edit] When i did the thermostat the water that came out was real dirty and brown , i only had a very small amount of g12 in the system i mostly used water (not smart i know , i was broke)

[CoyneJ]

Might be the water pump since the coolant is not resurculating

[TrillA4]

That's one of my thoughts , the water pump or a clogged radiator. ill have to check the rad when i get a chance and try to run water through it.

[CoyneJ]

Do you know if the water pump was the plastic one? Those usually fail, also you Wana use the coolant and distilled water to lubricate the water pump and prevent corrosion

[Seerlah]

You should be more concerned of those knock codes. If you overheat your engine too much you can warp it. Either that, or a bearing is messed up from overheating it. Or possibly...coolant went into the sump.

Coolant is there to cool the block. The block will continue to get hot due to combustion. Coolant cools both block and oil. If you are losing coolant, obvious you need to find out where you are losing it. But the knock could be an indication block is now warped and you have to get it pretty hot to do that.

Do you know what the oil temps were when overheating? Did you drain your oil to see how it looks. Going the extreme route here, but those cylinder knock codes are not good. Does your motor have an audible knock sound?

[TrillA4]

My temp gauge never got to the H symbol on the gauge only the dash before it (so there was still a like a mm between the needle and the h area ) then i would shut the car off or cool it down . I have yet to drain my oil but will do that soon, i didn't get a look at the oil temps unfortunately. The motor doesn't seem to have any audio knock to me but i cant be 100% sure . it sounds dumb but is it possible the knocks are cause by bad low octane gas?
The other thing that concerns me other than those new codes is that the bottom rad hose isnt getting hot.

Also water pump had metal impellers old plastic one broke apart , timing belt was done with waterpump, temp sensor is about 2 years old with 30-40k miles

[TrillA4]

My car is a mess here is more fault codes i had before i cleared the codes and drove it around the block

16395 - Bank 1: Camshaft A (Intake): Retard Setpoint not Reached (Over-Advanced)
P0011 - 35-10 - - - Intermittent

P0300 Diagnostic Code - Random Misfire

16687 - Cylinder 3: Misfire Detected
P0303 - 35-10 - - - Intermittent

P0304 AUDI - Cylinder 4 Misfire Detected

16686 - Cylinder 2: Misfire Detected
P0302 - 35-10 - - - Intermittent

P0507 Idle Air Control System RPM Higher Than Expected

Then a bunch of the knock codes

[Seerlah]

Not sure if this thread is a joke or not. One notch before H, that means your bock was well overheated. Should have also looked at your oil temp. That one is a tad bit more important than your coolant temp. Would not be suprised if you were 350*F oil temp.

NEVER run an overheating car. If reservoir empty and you continued driving, that motor is really hurting. Brute honesty is best at times vs giving false hope, and I think that block is done. Hard to correct damage caused by overheating.

Not at all am I saying to give up, but you need to stop driving that car and start diagnosing it.

[CoyneJ]

Rip engine, you had a good run

[TrillA4]

Threads not a joke I worded it strangely 2 dashes before H is where I would cool it off or turn it off and didn't drive it that way for long distance , once it got to that dash I would stop driving

[Seerlah]

You need to understand why that temp went up. There is something making that temp go up. And that is the engine block temp. You are not overheating the coolant. You are overhearing the block, and that temp is reflected in the oil and coolant temp. What I am saying is if your coolant temp was that high, your oil temp was also high. That is what you should be focusing on. You can always fix a high coolant temp. And capacity, which you explained earlier, is the reason why. But without the one thing that cools your engine existing...you overheated your motor. No getting around that. Know that and know you most possibly have a bigger issue at hand.

[LA4]

Is the B5 coolant temp gauge linear or threshold based? I always assumed it was just a threshold thing. Either way, that motor sounds like it got cooked.

[TrillA4]

I guess I should compression test it when I get a chance

[smokeyp97]

I have the same problem, i had a leak for a while and alwats lost coolant. I couldnt find where, it seemed like it was leaking from the block. I ended up using a mirror with an extention and checked the thermostat housing and it was warped from under and caused anti freeze to leak. Maybe that might be it . Just a suggestion

Sent from my SM-G935P using Audizine mobile app

[SN95Audi87]

My waterpump shattered 6-8 months ago while I was commuting from the city to the burbs. It actually happened in a ideal moment because it was a cool night. I managed to limp it home while the temperature gauge was at the 2-o'clock position. I had a few saving graces... #1) I was using Amsoil 5w40 synthetic Euro oil, it was really keeping the oil temps below 250 with no circulation #2) I cranked the heat up to MAX and put my windows down. #3) I parked it and had it towed to speed shop to get the timing belt and water pump done. The tech told me my waterpump was shattering in pieces. It was obviously the plastic version. I made sure to specify to use the improved metal pump when replacing.

I dont know if its too late for your engine! Hopefully not, but since these cars are nearing 15-20+ years old. A lot of things need to be check out. Anything rubber or plastic related should be replaced and thrown in the garbage. I still have a few hoses to go but my engine plumbing is almost all brand new. Lastly, make sure the hardware is up for the task.