Avensis t25 2.0 vvti - overheating during cold weather

[adilfc]

Hi all,

At the beginning - sorry for my English, i never got to learn a mechanic part of this language, so will use translator reg parts.

I lost all my hopes, as no one i went to is able to help me. I own my Toyota for over 7 years. The issue began last year. So basically i can see my engine is overheating, but only during winter. I'll put entire timeline of issue and repairs that has been done. Maybe anyone of you got any idea what is going on. 

Late autumn 2021

Engine started to overheating, i went to mechanic 1 and he replaced broken cooler. It was fine for 2-3 days and then it came back to same issue. Additionally i saw that fluid in the expansion tank dissaper to very minimum - i saw only a small portion on it in the wire. Any addition of it dissapeared once i drove like 20 km with new liquid. Went back to the mechanic and he told me it must be gasket under the head. Had no other symptoms related to it and it's 3rd time someone wanted to replace it, while it always was related to other issue.

Winter 2021\2022

I went to mechanic 2. He told me that cooling system needs to be vented. Then again it was fine for couple of days and problem came back. I'll add that engine temperature is going down to 90 degrees if i start to add gas and do the dynamic drive. 

Early spring 2022

I went back to mechanic 2 and he injected some fluid that supposed to plug the holes in my cooling system due to the fact that he hasn't seen any leaks through wires he has seen without removing parts of engine. 

Spring - Autumn 2022

All was fine, even tho I had same issue with dissapearing liquid, engine had a fine temperature. I drove few 200km rides and saw no issue

November 2022

Issue came back once i first had to remove ice from car windows. For example i went 10 km on the 'country road' and all was fine, but once i was coming back and entered my neighbourhood and drove carefully, engine was overheating again

January 2023

Only cold wind from air supply. Closed circuit has way more power than open one, but with open one, power increase with engine speed. I can see greasy traces on the dashboard. Engine is still overheating. 

Additionally, from the beginning, whenever i had no warm air from heating system, i know that engine will overheat. But once the air is warm, engine isn't overheating.

 

Anyone know what can cause the issue?

[avetoy]

A silly question: does the cooling fan (behind the radiator) work?

[adilfc]

Yes both fans are spinning 

[avetoy]

41 minutes ago, adilfc said:

Yes both fans are spinning 

One fan is for cooling radiator when car is not moving or moving slowly. The other should spin only when the AC is on.

How strong mixture is in the coolant?

And what do you mean by greasy traces on the dashboard?

Is there kind of sweet smell inside the car when engine is warm and heater blower is on? 

[adilfc]

I don't make a mixture but a coolant itself bought in 5 litres bottles. 

I tend to believe that these traces are caused by my e-cig, but since last year I'm using way more the second car and this isn't happening there, so definitely something comes from inside. Additionally it's a lot of fog on windows during rainy weather, way more than in other cars. Just check comparision from few days ago vs random red car that was standing next to mine. 

 

Sometimes i tend to smell a sweet inside, but it's not a rule to feel it all the time. 

[avetoy]

My wild guess is that there is a leak in the heater or its hose.

To be sure, the heating system should be pressure tested.

I´m afraid no stop-leak liquids will help to fix those kind of leaks.

But like I said, this is just a guess! You need to get a second opinion from a trusted mechanic.

One thing you could do: check the floor coverings under the dash? If they are wet with coolant...

[Sooty]

I agree that it sounds like the heater matrix is leaking.

During hot weather you have the heater set to cold or turned off. This will stop or at least slow down the leak.

In cold weather you turn the heat up to full which allows full flow and pressure of the coolant to pass through the heater matrix and thus leak more.

I suggest the same as Avetoy and get the heater system pressure tested.

[DerekHa]

Have just read your topic Adrian and agree with the replies given by Avetoy and Sooty.

This wouldn't be an idle solution during any sort of cold weather like we're having at the moment but!!

In better more clement weather you could disconnect the two hoses in the engine compartment that input and return the hot coolant to the heater matrix. Take another piece of suitable length and diameter hose and link the input feed and return from the engine together, you'll be effectively taking the heater matrix out of the coolant circulation circuit. This would allow you to remove the leaking heater matrix for repair/replacement but still be able to use the car.

Obviously you'll have the task of drying out your windows, carpet and any sound insulation beneath that to stop the internal condensation.

[adilfc]

Hi all, 

Thanks for your replies. This was also my initial thought. 

 

Do you know if there is any manual how to replave heater matrix in my Avensis t25 2.0 vvti 2003? I already spoke to 2 mechanics and they don't want to do it as it take too long to do it all, especially due to the fact that new heater matrixes aren't available in my country, hence all that can be done is to send old one for renovation or buy used one from broken car. 

[avetoy]

No idea where to get the manual but here is a pic about heating device:

 

It seems to be quite laborious to disassemble! No wonder if those mechanics don´t want to do it.

I´ve  never done it but I think it is not that  difficult. Just have to be flexible and patient.

Mr. DerekHa suggested a good solution to bypass the heating device so the car can be still driven during the repair.  And then it would be easy to do a pressure test too, just to be sure.

 

[DerekHa]

7 hours ago, avetoy said:

No idea where to get the manual but here is a pic about heating device:

 

It seems to be quite laborious to disassemble! No wonder if those mechanics don´t want to do it.

I´ve  never done it but I think it is not that  difficult. Just have to be flexible and patient.

Mr. DerekHa suggested a good solution to bypass the heating device so the car can be still driven during the repair.  And then it would be easy to do a pressure test too, just to be sure.

 

Hi again Adrian,

I've no experience of working on your vehicle so can't give any advice that's vehicle specific.

However going back some years now I was persuaded to buy a Renault Scenic, had various problems with the thing but the most frustrating was the fact that blower motor blew up while away from home. On a long weekend, the heater blower started to complain. It got worse suddenly and then completely failed expelling shards of plastic out of the air vents into the car and promptly stopped working.

After returning home researched this hoping the blower would be an easy replacement! It was a nightmare entailing the entire dashboard, centre console, passenger seat being taken out of the vehicle and dropping the steering column to access it. Had my son helping and it took us three days in all! Lots of cursing and skinned knuckles but it got replaced. Will depend on how confident you are, have the space and if you're good with spanners etc.

Have a feeling there was some one here a few weeks back wanting to swap one Avenis dashboard for another, can't remember the model or why he wanted to. If you can find his post it might help you figure out how to go about tackling your heater matrix if that is the problem.

[DerekHa]

This video may give you some idea of how to take the upper dashboard out.

[avetoy]

The guy in the video really knew what he was doing i.e. he has done it many times before! 

Some sources say no need to remove the upper dash to get to the heater matrix?

The A/C can also cause troubles. Some say the heater and A/C cells must be disassembled together? The A/C system must therefore be drained, etc...

About the manuals: I read that maybe Haynes had a manual for Avensis T25, but as far as I know, they are generally quite ... simple

[avetoy]

Managed to find a video about Avensis T25 heater device removal. Seems to be diesel car but I think it is the same inside.

I wrote earlier that according to some sources the dash does not need to be removed to get to the heater matrix... Now after watching the video I strongly doubt it!

[avensis_2018]

don't go breaking all the car ...

first, i would buy a new water coolant cup, and see if it got solved,  then i would only take the thermostat out and drive it for a week to see if it got solved.

then open it again and put a new thermostat, or just replace the thermostat and that's it.

good luck.