B5 A4 1.8T manual not getting up to temp

[jetice91]

I have tried replacing the coolant temp sensor and the thermostat, and also did a coolant flush. The oil temp sensor shows that the car is getting warm, and it has warm air out of the HVAC.

When driving around, the car never gets up to temp. If I just let the car sit and idle, the coolant temp gauge gets up to temp after a long time (around 1 hour). However, if I let the car idle up to temp, then go out and drive it, it will return to cold after only a couple miles. Does anybody have any ideas?

[seanf86]

I have tried replacing the coolant temp sensor and the thermostat, and also did a coolant flush. The oil temp sensor shows that the car is getting warm, and it has warm air out of the HVAC.

When driving around, the car never gets up to temp. If I just let the car sit and idle, the coolant temp gauge gets up to temp after a long time (around 1 hour). However, if I let the car idle up to temp, then go out and drive it, it will return to cold after only a couple miles. Does anybody have any ideas?

how high is the fan speed? my 97 doesnt get up to temp on my 10km drive to work unless I keep the fan as low as possible until the temp guage reaches the middle otherwise it goes 1/4 way up until the cabin warms up. What brand coolant temp sensor did you use, I bought a cheap one and it didnt work properly, spring for an oem one from the dealer.

[jetice91]

how high is the fan speed? my 97 doesnt get up to temp on my 10km drive to work unless I keep the fan as low as possible until the temp guage reaches the middle otherwise it goes 1/4 way up until the cabin warms up. What brand coolant temp sensor did you use, I bought a cheap one and it didnt work properly, spring for an oem one from the dealer.

Fan speed is off. I have driven this car on multiple 100+ mile trips now, and it has never gotten to temp during driving. If I shut the car off after driving it for a while, and let it sit, when I get back in, the coolant temp has risen up. This makes me think that there is something in the coolant loop that is keeping it from getting to temp.
Also, here is the temp sensor and thermostat I bought.
http://www.ecstuning.com/ES2628655/
http://www.ecstuning.com/ES2581867/

[seanf86]

do you have vag com? if the oil temp is going up so is the coolant temp as the oil cooler warms/cools the oil based on coolant temp. Check the cluster display with vag com vs the ecm for coolant temp, fiancee has a 2.8 b5 and the ecm portion of the sensor is fine but the cluster side is done, vag com says the temp on the cluster is 30C vs the ecu reading 92C. I'd try a new dealer sensor, I put a uroparts one in my 1.8t and it was junk. OEM all the way.

have you always had this problem? even with the old t stat/ cts? In the past with my old cars being gm and dodges aftermarket t stats were junk, I had to get genuine GM/ac delco/mopar t stats or I'd forever have heating issues.

[jetice91]

do you have vag com? if the oil temp is going up so is the coolant temp as the oil cooler warms/cools the oil based on coolant temp. Check the cluster display with vag com vs the ecm for coolant temp, fiancee has a 2.8 b5 and the ecm portion of the sensor is fine but the cluster side is done, vag com says the temp on the cluster is 30C vs the ecu reading 92C. I'd try a new dealer sensor, I put a uroparts one in my 1.8t and it was junk. OEM all the way.

have you always had this problem? even with the old t stat/ cts? In the past with my old cars being gm and dodges aftermarket t stats were junk, I had to get genuine GM/ac delco/mopar t stats or I'd forever have heating issues.

Just confirmed with VCDS, temp gauge is accurate. Also, I have only owned the car 4 months, and it never got up to temp before either.
I don't know where you were getting your aftermarket parts from for the Big 3 cars, but in the 10 years that I have been working on them, never have I had any issues with aftermarket parts.

[SanFrancesc0]

Mine does the exact same thing! I replaced my cts with an oem one and still same thing. Im thinking it has something to do with the wiring as my oil temp works and so does my heater and i know my car is warm but the needle always says cool.

Someone care to chime in with a solution? It would be much much appreciated

1999.5 1.8TQM

[M-Hood]

Have you tried checking the coolant temp manually to see if there is an issue with the wiring of the temp sensor?

[ECS Tuning-Audi]

Verify that the thermostat is working. If its stuck open it could very easily cause the coolant to not reach operating temp. Pull the thermostat out, boil some water, Put the thermostat in the boiling water. If it opens it's good if nothing happens it has failed.

Jason

[SanFrancesc0]

Verify that the thermostat is working. If its stuck open it could very easily cause the coolant to reach operating temp. Pull the thermostat out, boil some water, Put the thermostat in the boiling water. If it opens it's good if nothing happens it has failed.

Jason

Wow I would have never thought of that! Thanks for the pro tip ;)

I am pretty sure that its not the thermostat though the previous owner replaced it 30k ish miles ago. And the fact that it reads the correct temperature after sitting for a while makes it even stranger. Ill definitely check my thermostat out though and report back. I really want to get this whole issue resolved as im sure Jetice91 and I are having the same problem and if we both have had the same issue im sure siomeone else has and will be able to give an answer

[OldAudiA4]

I have never considered that there was a problem with my car but my car does take a very long time to reach 90 degrees. On a short drive, it would not hit that temperature. It hovers a little above 60 degrees for a while. I've never thought of it as a problem though.

If the temperature gauge moves off dead cold, does that indicate that the thermostat has opened?

[ECS Tuning-Audi]

Wow I would have never thought of that! Thanks for the pro tip ;)

I am pretty sure that its not the thermostat though the previous owner replaced it 30k ish miles ago. And the fact that it reads the correct temperature after sitting for a while makes it even stranger. Ill definitely check my thermostat out though and report back. I really want to get this whole issue resolved as im sure Jetice91 and I are having the same problem and if we both have had the same issue im sure siomeone else has and will be able to give an answer

I've seen thermostats fail in less time. Depending on which unit was installed some aftermarket thermostats are poor quality and will fail prematurely.

I have never considered that there was a problem with my car but my car does take a very long time to reach 90 degrees. On a short drive, it would not hit that temperature. It hovers a little above 60 degrees for a while. I've never thought of it as a problem though.

If the temperature gauge moves off dead cold, does that indicate that the thermostat has opened?

The thermostat only opens once the car reaches operating temperature. Once it's reach operating temp it then cycles opening and closing to regulate the coolant temp.

Jason

[SanFrancesc0]

I have never considered that there was a problem with my car but my car does take a very long time to reach 90 degrees. On a short drive, it would not hit that temperature. It hovers a little above 60 degrees for a while. I've never thought of it as a problem though.

If the temperature gauge moves off dead cold, does that indicate that the thermostat has opened?

Jason from ECS knows what he's talking about

But as for your issue it is slightly different than the issue that we are having. Our issue is a constant low temperature reading for the coolant. Even after an hour+ of HARD "touge" driving the dial still reads as C or L whatever the bottom is. After shutting the car off and waiting some time restarting it seems to show, atleast what I believe to be, the correct temperature on the dial. Once I start driving again though it goes back down and never goes back up to temperature. I know it cant be cold because the oil temperature is well within operating temperature and my heater works as well (not hot but definitely enough to warm the car up in the cabin). Which all makes me believe its just an electrical issue. Possibly a bad contact or a wire that is breaking but its all so strange as it never goes up even after driving. Im so stumped.

I've seen thermostats fail in less time. Depending on which unit was installed some aftermarket thermostats are poor quality and will fail prematurely.

Im planning on pulling the thermostat though and boiling it to check if it opens or not and see if it is possibly the issue. Hopefully we can get this mystery solved! I am able to use vcds to log and check data. Where would I go to look for the temperatures?

I feel like I have kinda thread jacked this haha. I posted a thread about this issue plus a couple others a while ago and nobody really could find a solution.

Anyways I have little to no electrical knowledge and I would like to avoid having to deal with a mechanic as my pockets are not very deep and I prefer to do the work myself to not only save money as I'm a college student, but also to learn how to do things and how they work as I am trying to major in Automotive Engineering

[ECS Tuning-Audi]

Jason from ECS knows what he's talking about

But as for your issue it is slightly different than the issue that we are having. Our issue is a constant low temperature reading for the coolant. Even after an hour+ of HARD "touge" driving the dial still reads as C or L whatever the bottom is. After shutting the car off and waiting some time restarting it seems to show, atleast what I believe to be, the correct temperature on the dial. Once I start driving again though it goes back down and never goes back up to temperature. I know it cant be cold because the oil temperature is well within operating temperature and my heater works as well (not hot but definitely enough to warm the car up in the cabin). Which all makes me believe its just an electrical issue. Possibly a bad contact or a wire that is breaking but its all so strange as it never goes up even after driving. Im so stumped.





Im planning on pulling the thermostat though and boiling it to check if it opens or not and see if it is possibly the issue. Hopefully we can get this mystery solved! I am able to use vcds to log and check data. Where would I go to look for the temperatures?

I feel like I have kinda thread jacked this haha. I posted a thread about this issue plus a couple others a while ago and nobody really could find a solution.

Anyways I have little to no electrical knowledge and I would like to avoid having to deal with a mechanic as my pockets are not very deep and I prefer to do the work myself to not only save money as I'm a college student, but also to learn how to do things and how they work as I am trying to major in Automotive Engineering

I've had a love hate relationship with these 1.8T motors for over 8 years and doing the majority of the work myself I would hope I'd pick up a thing or two along the way! I've used these forums to learn an exceptional amount of information so it's only right to give back!

I had a very similar issue as yours with my B5 heat would blow hot and the temp would never hit normal when it was below about 50 degrees. From my understanding it was the thermostat that stuck open. I'll explain why in a second.

When the thermostat sticks open it allows constant coolant to flow through the cooling system and never really gets a chance to reach the normal temp of 210 degrees (when its cool out). You still have heat because the heater core still gets pretty hot as it will store the heat since the only air flow it gets is the fans pushing through it for the climate control, which is not enough to cool it like a radiator in the front of the vehicle.

When you park your car the temp goes up because the coolant isn't circulating and obviously since the car is off you wouldn't see the needle go up. When you restart the car later on, the coolant near the sensor has just been sitting so it's absorbed heat through conduction from the hot block, and can easily heat soak other plastic parts under the hood. Once you start driving again the coolant will continue to circulate since the thermostat is wide open. Normally it would stay shut until it gets to the point it needs to open.

I hope this helps!

Jason

[sa_seahawker]

FWIW, I'm having a similar problem with my B6 1.8. I've already swapped out water pump, two thermostats, 4 CTS sensors, rear flange, two heater hoses, two reservoirs and caps, and the heater core...still the same problem. I managed to get heat at high RPMs but today, the heat just went away altogether. It takes me 15 minutes at high revving to get temp up.

All parts are OEM and the thermostat and heater core were just swapped out within the week (along with 4 coolant flushes). I'm still trying to figure out if there's a bubble still in there. That's the only diagnosis I can come up with seeing as how the entire coolant system is brand new. Audi/VW coolant systems are retarded.

[BaseDrifter]

^At that point I would start thinking you have a clogged passageway somewhere.

[Jerstillman]

Or an airpocket. Did you guys put the heater hose back to the little hole while filling your cooling system to purge the air out of your heater core?

Sent from my SCH-I545 using Tapatalk

[OldAudiA4]

Generally speaking does anybody else notice that the Audi A4 takes longer to warm up and reach operating temperature than other cars?

It's 27c here at the moment. My car was cold. I started it and let it idle for approx. 10 minutes. It reached 70c on the coolant temperature gauge. Both hoses were hot and getting warmer with the top hose always hotter than the bottom hose.

With the thermostat being on the bottom hose on this car, how does that work? I'm used to cars with the thermostat up the top somewhere. What temperature is the thermostat supposed to open on these cars?

[Sp00led]

I used to have the exact same problem.. Could drive for hours and temp gauge wouldn't pass 1/3 on the gauge. Heater wouldn't blow hot and it was super frustrating. Before you go replacing thermostat or any other repair, you should make sure there're no air locks in your cooling system.
Remove the plastic cover that covers your first firewall (the area where your battery is). Once that's off you can find the accordian looking cover on the drivers side, that protects the two coolant hoses going to heater core. Pull the accordian ish cover back to reveal the two hoses. Remove or back the clamp off the left hose until you see a little bleed hole. With that bleed hole visible, squeeze (massage) your upper rad hose by the rad up front. Keep massaging the upper rad hose until you get a fairly steady flow of coolant coming from the bleed hole. Then push hose back over bleed hole and tighten/replace clamp. Recover hoses with accordian type cover and put rest of cover back on and voila.. Easy as that.
My car blows about 50x hotter now and the coolant temp gauge gets up to temp (right in the middle is normal) way faster.

Hope some of that can help.
Feel free to shoot me a message if something doesn't make sense.

[OldAudiA4]

When the car is warming up, should both radiator hoses be gradually getting warmer or should one of them be pretty cold and then get very warm once the thermostat opens? On my car after idling for 10 minutes, both hoses get gradually warmer with the top one being hotter than the bottom one but to reach operating temperature, I would have to drive around a fair bit to get it there.

[Jerstillman]

Top one should be hot and bottom should be cold until thermostat opens allowing the water from the radiator to enter. Sounds like A) you have a partially stuck open thermostat
B) you have an air pocket.

Sent from my SCH-I545 using Tapatalk

[OldAudiA4]

Replaced the thermostat. On the single drive I've taken it for it got up to 90c a lot quicker and stayed there the whole journey, so looks like that has fixed it.

[sa_seahawker]

Disregard on mine...blown head gasket.

[jetice91]

What brand coolant temp sensor did you use, I bought a cheap one and it didnt work properly, spring for an oem one from the dealer.

And we have a Winner! I replaced the CTS with an OEM one, and all is good.

[StanGetz]

Had this problem too. OEM thermostat did nothing, OEM CTS worked well. Car warms up quick and stays right in the middle.

Now I have to get the oil one worked out.

[sa_seahawker]

I was just about to dive into my head gasket when a thought just occurred to me...

My oil isn't milky and I'm not losing coolant, im just having problems heating the inside and cooling the motor...

Head gasket = unlikely? Thoughts?

Although it did get pretty hot before I shut it down....

[OldAudiA4]

Had this problem too. OEM thermostat did nothing, OEM CTS worked well. Car warms up quick and stays right in the middle.

Now I have to get the oil one worked out.

I might be stating the obvious but I found that after I replaced the thermostat and the car was running properly at 90c where it should be, the oil temp gauge sat higher than it was pre-thermostat. I think it usually sits about 75c and doesn't budge off there.

[OldAudiA4]

I was just about to dive into my head gasket when a thought just occurred to me...

My oil isn't milky and I'm not losing coolant, im just having problems heating the inside and cooling the motor...

Head gasket = unlikely? Thoughts?

Although it did get pretty hot before I shut it down....

Well I don't think it would be the thermostat as if it fails, it fails in the open position and leaves the car running cooler than it should be.

Air in the system?
Is the fan/s working?

[sa_seahawker]

Well I don't think it would be the thermostat as if it fails, it fails in the open position and leaves the car running cooler than it should be.

Air in the system?
Is the fan/s working?

Fans work for sure. I had shop pressure bleed it. Although a new development happened now. Car started misfiring in cyl 1,3,4. Swapped out red tops for original and now misfire in 2?! LoL.

But I don't think a timing issue would produce coolant issues...

[azsuprasm]

Why start a new thread when this one will do?

My '01 AWM B5 1.8t Avant. Tstat replaced 2 years ago, gauge worked fine until about a month ago: gauge would intermittently work and then not, and now more not. Diag: another dead Tstat.

Just finished process and lo, still no temp on the H2O gauge. Top hose is hot, lower hose is annoyingly cool. New Diag: A bad new Tstat (it happens).

In the mean time, I read the posts about the CTS (Coolant Temp Sensor) on the back of the head, but to me, it looks as if the temps are taken at the bottom sensor; you know, the one you remove when you're purging the coolant?

Tomorrow AM, I'm going to try another Tstat; I'll buy 3 of them, boil them and keep the one that opens up. I'll also take the time to flush the heater core when the coolant is out and chase the tap water with distilled (from a make-shift beer bong) so I don't leave yucky water in my core. I'll also buy a Green CTS w/O-ring and have that in my pocket, just in case.

Summer is upon us in AZ, so I hope this works. If not, we'll chat about coolant temp sensors again, and you folks can let me know exactly what the sensor is at the bottom of the rad. hose (3 wires).

Thanks! -=S=-

[OldAudiA4]

Why start a new thread when this one will do?

My '01 AWM B5 1.8t Avant. Tstat replaced 2 years ago, gauge worked fine until about a month ago: guage would intermittently work and then not, and now more not. Diag: another dead Tstat.

Just finished process and lo, still no temp on the H2O gauge. Top hose is hot, lower hose is annoyingly cool. New Diag: A bad new Tstat (it happens).

In the mean time, I read the posts about the CTS (Coolant Temp Sensor) on the back of the head, but to me, it looks as if the temps are taken at the bottom sensor; you know, the one you remove when you're purging the coolant?

Tomorrow AM, I'm going to try another Tstat; I'll buy 3 of them, boil them and keep the one that opens up. I'll also take the time to flush the heater core when the coolant is out and chase the tap water with distilled (from a make-shift beer bong) so I don't leave yucky water in my core. I'll also buy a Green CTS w/O-ring and have that in my pocket, just in case.

Summer is upon us in AZ, so I hope this works. If not, we'll chat about coolant temp sensors again, and you folks can let me know exactly what the sensor is at the bottom of the rad. hose (3 wires).

Thanks! -=S=-

I hope you are not buying genuine thermostats because where I am they are $92AUD each!

Because the gauge would work and then not, my gut feeling would not be thermostat? Perhaps CTS?

When my thermostat went, because it fails in the open position it acted as so, would take much longer to get to operating temperature. and on highways would be running slightly under optimum operating temperature (which I think is 88C). It never really had an effect on the gauge not working.

[azsuprasm]

Yes, at WOT (wide open thermostat. Heeeheee), it would take much longer to get to op. temp, esp. when it's cold out. My issue is that at 92* F today, the car heats up by looking at it; Top hose hot, bottom one still cool. I'm about 90% sure it's a dead (closed) Tstat. Oh, and yes, they're the $15 USD ones at O'Reilly auto parts.

[StanGetz]

Mine did the same like I said, Tstat didn't help. CTS all the way for me. Been good from -5 to 87 degrees thus far.

[azsuprasm]

Mine did the same like I said, Tstat didn't help. CTS all the way for me. Been good from -5 to 87 degrees thus far.

If I felt that the bottom hose was also hot and still no reading on the gauge, then I'd be 90% that way.

Back of the head or the one on the lower hose? (What is that sensor for folks? Someone please tell me!).

Oh, and Stan; I play a YTS-62 w/B.Dukoff powerchamber. Have lower end alto & sop for kicks.

[StanGetz]

If I felt that the bottom hose was also hot and still no reading on the gauge, then I'd be 90% that way.

Back of the head or the one on the lower hose? (What is that sensor for folks? Someone please tell me!).

Oh, and Stan; I play a YTS-62 w/B.Dukoff powerchamber. Have lower end alto & sop for kicks.

Pretty baller, bro

[azsuprasm]

Steve's '01 A4 B5 Avant 1.8t 5spd update:

Got the second Tstat, boiled it, opened up like a clam. CHECK.
Drained the coolant again, replaced it again. All from the TOP of the motor. CHECK.

Still no Coolant temp on gauge. Drained coolant a 3rd time, changed CTS with cheap-o from O'Reilly.

Works like a charm. Although the lower hose isn't getting hot too quickly, the temp gauge stays rock-steady up the middle even with spirited freeway driving here in 100+ F Degree heat. DONE!

Thanks to the group and to AudiZine for the forum.

-=S=-