Alphard hybrid 2.4 Petrol - NEVER USE ENGINE BRAKING

[John Hollis]

Here is a reposting of a report I posted in 2021 on 2.4 litre engine failures.  The engine was over-developed and has a very high compression ratio, so when downhill engine braking is used, it sucks up ALL the oil with the high vacuum created and burns it off on the piston rings!  Leads to engine failure and blown gaskets. I now go carefully down hills using the brake, not putting the car into a lower gear!. The relevant info is in the last third of the report on yellowish pages.

 

1206360494_ToyotaAZseriesengine.pdf

[Rojie]

As my beloved Father used to say "Brakes are cheaper than Engines or Gearboxes".

And I say "Just make sure you don't fry your brakes !

 

Anyone been to Widdecombe (in the Moor) from Bovey Tracey ?

 

Many drivers roast their brakes on the downhill approach !

 

!

[pipsyp]

I know it's rather made clear in the title, but this wouldn't affect the regular EFI 2.4's for anyone wondering.

 

The AH10 hybrid had a particular development of the 2AZ engine that had direct injection and a higher compression ratio.  I guess as well as this issue, they are probably more susceptible to valve coking as well (as the valves don't get washed with fuel during the injection cycle as they would do with the regular port injection motor).

[smurf]

From what I have read, the oil consumption issue only affected engines made in the USA and had something to do with the piston rings used during the initial engine build. This would make sense as the official repair was new rings and pistons rather than a fundamental engine flaw that requires significant modifications to resolve. It definitely affected the non hybrid 2.4 engines as the recall covered the 2AZ-FE engine as well, and I don't believe that either the 2AZ-FE or the 2AZ-FZE have direct injection. 

 

I'm not sure how it would be possible to avoid high manifold vacuum when going downhill with the foot off the accelerator? No amount of pressing of the brake pedal will change the fact the engine is still turning and trying to suck in air through a closed throttle.

Edited February 14 by smurf
Extra info

[pipsyp]

8 hours ago, smurf said:

From what I have read, the oil consumption issue only affected engines made in the USA and had something to do with the piston rings used during the initial engine build. This would make sense as the official repair was new rings and pistons rather than a fundamental engine flaw that requires significant modifications to resolve. It definitely affected the non hybrid 2.4 engines as the recall covered the 2AZ-FE engine as well, and I don't believe that either the 2AZ-FE or the 2AZ-FZE have direct injection. 

 

I'm not sure how it would be possible to avoid high manifold vacuum when going downhill with the foot off the accelerator? No amount of pressing of the brake pedal will change the fact the engine is still turning and trying to suck in air through a closed throttle.

Absolutely right sorry, I'm confusing it with the FSE that came later.  Same engine this but Atkinson cycle hence lower power and torque but higher compression ratio/efficiency etc

 

Agreed I dont think the oil burning issue affected the Japanese made motors greatly either, was rather endemic in the US by all accounts!

[MarkATH10W]

If you read my threads, I suffered an engine failure and no start.  Japanese mechanic found evidence of blown engine.  This occurred up a steep incline @ highway speeds while stressing the engine.

 

Good luck.  I roughly had my vehicle for 2 months.  It is now being shipped off to the wreckers with approx 110 thousand km.

 

I will not be buying another ATH10W; nothing to support their repairs in north america.

[Rojie]

17 hours ago, MarkATH10W said:

If you read my threads, I suffered an engine failure and no start.  Japanese mechanic found evidence of blown engine.  This occurred up a steep incline @ highway speeds while stressing the engine.

 

Good luck.  I roughly had my vehicle for 2 months.  It is now being shipped off to the wreckers with approx 110 thousand km.

 

I will not be buying another ATH10W; nothing to support their repairs in north america.

 

I am very sorry to hear of your experience.

 

Had you been using engine braking a lot. Clearly you wouldn't be whilst driving uphill.

So I am assuming that you suspect that prior engine braking was the cause.

 

Had you been ensuring correct engine oil levels and renewing the engine oil after  reasonable periods.

 

I can't speak for BC, but even in the UK finding a suitable mechanic can be an issue.

[MarkATH10W]

• Regarding engine braking; yes I used that in the past.  I did not know about engine braking issue until literally this week.  breakdown occurred last summer, and finally diagnosed a week ago.
• Engine oil was fresh full synthetic with new denso filter.
• Notable observations at time of import:
  • visible valves under the oil cap showed darkened / hardened build up; I have never seen this in any of my other previous toyota's (all 5-6 of them), which were generally remarkably clean.
  • one of the valve cover bolts was different in appearance; is that standard? or evidence of previous repair work?
  • fresh off the boat, the vehicle stuttered due to an extremely dirty MAF sensor.  problems went away
  • engine seemed "loud", unrecognizable sounds that I attributed to hybrid system when vehicle was apparent. only occured sometimes.

 

 

[Rojie]

Reading Paul's (pipsyp) input I am reminded that very high compression engines do not 'tolerate' high alcohol content fuels very well..

E10, as we call it in the UK.

[MarkATH10W]

21 hours ago, Rojie said:

Reading Paul's (pipsyp) input I am reminded that very high compression engines do not 'tolerate' high alcohol content fuels very well..

E10, as we call it in the UK.

Interesting.  I thought that alcohols allowed for higher compression, without actually increasing the octane rating.

[smurf]

Ethanol is used as an octane booster and high ethanol content fuels (such as E85) are deliberately used in high compression engines such as race cars. I can't say I have heard of any detrimental affects to engines from the combustion of the relatively low amount of ethanol found in pump fuel. 

Edited March 13 by smurf

[Rojie]

I have certainly read that engines using direct injection are not suitable for E10 use.

 

I wish I could remember where I read it, (if I did).

 

I did do a lot of research into E10 at the time it was introduced.

I need to research my research !

 

There was a large debate in this forum regarding whether members should use E5 (Super unleaded) or the new E10 in their Alphies.

[Rojie]

Yes. I was confusing myself.

 

Avensis 2.0 litre with engine 1AZ-FSE made between July 2000 and October 2008.
Avensis 2.4 litre with engine 2AZ-FSE made between June 2003 and October 2008.
These models, and those produced before 1998, should continue to use E5.

 

It is the 2AZ-FSE that was the problem; not the 2AZ-FE.

 

Sincerest apologies for any alarm I may have caused.

[MarkATH10W]

to be precise. is there any reported issue with the 2AZ-FXE?

 

[arthurj]

On 3/13/2024 at 8:33 PM, MarkATH10W said:

to be precise. is there any reported issue with the 2AZ-FXE?

 

Not the same issue, but my ATH20 with the same engine did have a piston rebuild in Japan due to recall. I haven’t heard of any others that have gone through this process though, it think it may have only affected a small number of cars.

The hybrid works in quite a different way to the standard petrol. Similar engine but it uses a different cycle and pressure build up due to engine braking is not an issue because hybrids simply don’t do it.