2004 M6 overheating
 

hi mazda fans,
I have 2004, 2.0L, 100kW diesel hatchback mazda 6 (283 000 km). Spring 2012 I took it to service for water pump replacement and things around, few weeks after thermostat burned (it was not replaced before). I had it replaced and all worked fine till about a month ago. It was hot day and I had AC on and we were going up the hill when I noticed that engine temperature was raising fast. I turned off AC and it went fast down after that. It was fine since then till last weekend. Car fully loaded (4 adults, child and full trunk). Doing 140km/h on highway, AC on and engine temperature started to raise sudenly so I turned off AC again but it didn't help. Then I noticed we were going up the hill again. After we climbed over it, temperature went down again very fast. I have checked lot of posts here and consulted with friends where can be the problem. We figured out it can either be thermostat - not opening fully and so when engine is put under load it is not able to cool it down fast enough. Or the 2nd option we found is turbo intercooler not working properly. In december the pipe from turbo to intercooler didn't make it and I had to drive 60km to nearest service. Last 2 or 3 weeks I am noticing that my mazda is not giving enough HP when I need it, but only sometimes. So far it looks like when I shift up to 4 or 5. Feels almost same like when turbo kicks in at about 1600rpm but I am over 2000rpm and speed is not going up fast like it used to/like it should. when I don't shift for while and step on the gas I can clearly feel when turbo kicks in around 1600rpm. So we figured out that this overheating problem might be somehow connected with this HP loss problem = turbo or intercooler. What do you think. or it might be something else?

Rasto

Check coolant levels and try a coolant flush. It could also be air in your coolant lines, burping the air from them should help things.

Sounds like the engine is taking a bit more time to create the boost needed. Have all of the turbo related piping checked for leaks.

Air leaks in intercooler is a good place to start.

Hi, thanks for answers.
I check coolant level regularly, never had to add any. It's now at full line.
I will go to mazda dealer this week to let them check intercooler.
thanks again, will let you know.

R

Hi, cooler cleaned, same as turbo and EGR valve. It's not so hot outside since then but there was no problem with overheating anymore. Also I don't feel HP degradation that much now, it comes back sometimes but it's not that bad as before.

When the weather is hot you will feel like the boost is down and this is normal. The intercooler is there to cool down the air temp for the turbo so when its hot outside the air temp in the intercooler stops hot. When the weather is cold your car will boost 100% better because the air temp is alot colder and that's when a turbo is working at its best.

Take a look at the size of the intercooler on a big horsepower car and the reason they are that big is to try and cool down the air temps more so the turbo does not over heat and loose boost. Then take a look at the size of your intercooler and you will see why they don't really work to well on a hot day. Over here in the UK its always cold so we don't really notice the difference with our cars.

hi there again, story continues,
my mazda was in service again, it was still overheating. So they tried to replace thermostat. Told me there was wrong one inserted and it was also a bit twisted. anyway that was not it. engine is still overheating in hot weather and under load. some strange things I noticed. When I enter hightway it takes 10-15 minutes till it starts overheating. now also on the flat road, no hills and 130km/h, outside temp over 30 degrees celsius. week ago I checked collant level and it was at the low line - loosing it, this never happened before. btw, coolant was replaced twice since so do you think it can still be air inside?
Something is leaking from intercooler. One drop each day, black but not slicky like oil.
Lost of horse power problem - turbo 'kick in' is not noticable anymore. sometimes the car accelerates fine starting over 2000rpm, sometime it feels like turbodiesel without turbo. also some days I am noticing very heavy smoke from exhaust when I step on the gas more - poor acceleration. when it accelerates fine I don't see that much smoke behind me or don't see any at all. any way how to test if turbo is fine (I know it most probably is not) but I want to avoid changing it and then realising it was not it.
And climbing up the hill is only possible with higher rpm, over 2400, otherwise it's going down. before when I didn't have these problems car was able to climb steep hills at ~2000 rpm.

One more thing with overheating, one cooler day I was on the way driving up to steep hill for about 10 minutes pretty fast. cooling was ok, then I stoped for about 5 minutes. when I came back and wanted to start the engine I noticed that temperature was between normal and high, engine overheated when it was turned off, I never saw this happening before. After I started it took about 5 seconds and engine temp was back to normal.

Rasto