rx400H engine noisy on start up but gradually settle down

[mikesands]

When the car is first started from cold, the engine is so noisy that it sounds like there's a hole in the exhaust, after about 30 seconds it quietens down to about half the volume (but is still too noisy).  After driving for a few minutes the engine noise level drops to about normal.

Anyone any ideas what I should check?

Mike

PS - from outside the car the noise seems to be coming from high up rather than low down where the main part of the exhaust system is .... but I might be wrong

[Brian26]

From experience ( not with a Lexus) I would check exhaust manifold bolts and gasket ( I had one  of the manifold bolts shear on another vehicle causing a leak ) followed by any other joints on the exhaust system. It sounds like a leak that is taken up as the exhaust system warmes up..

Bri

[ColinBarber]

The exhaust manifolds aren't cast so unlikely to be a crack in one of them. As Brain says, check the manifold bolts, the welds around where the primary cats are attached to the manifold and the joints to the exhaust.

[mikesands]

Thanks - I will get those checked tomorrow

Mike

[kenhall]

There are three mild steel clamps where the two manifolds come together into one. On my RX these clamps had badly corroded and were starting to split apart, however without any obvious leakage. I’ve replaced them with stainless clamps.

[mikesands]

I thought I would open up the bonnet lid when I started the car this morning, and now I'm thinking the noise is more an intake noise.  It definitely reduces after 30 seconds when the fuelling changes.  And it seems to be coming from the mid/left side as I look into the engine bay from the front of the car (ie the side where the Battery is but not that far over)

Mike

[ColinBarber]

are you able to record the sound?

[mikesands]

Hmmmm - it seems the fault was the 'temporary' fix my mechanic did about 18 months ago in the exhaust system.  I shouldn't complain since it was only paste and it's lasted 18 months.  But he says the back box of the system is fine and the top end is fine, but there are 3 sections of pipe in between that are paper thin and the flanges and joints are badly corroded.  Does anyone know of a source in the UK where I could buy these bits?  Just the one section of pipe that he has pasted twice was £400 from Lexus last time we looked at it.

Thanks

Mike

[Brian26]

I believe people have had some success here. I have never used them myself though.

Bri

 

  https://www.tonybanks.co.uk/exhausts/

[mikesands]

Thanks Brian - I have emailed them, and they aren't too far from me

Mike

[mikesands]

just an update on this.  I took the car to an exhaust specialist (one-man band) in Middlesbrough and we looked underneath the car on his lift.  The whole exhaust was in surprisingly good condition for 172k miles (and he said it wasn't stainless).  Anyway the problem was being caused by a fracture around what he said was a resonance damping weight that Lexus have designed into the long pipe between two of the boxes.  Today he sleeved that pipe all the way to the back box and welded the balance weight as accurately as he could into the original position.  And it's worked.  Much quieter.  He's sending me some pics later which I will post.  £200 total.

Mike

[Brian26]

Pleased you have it sorted Mike.

[mikesands]

4 minutes ago, Brian26 said:

Pleased you have it sorted Mike.

well ......  yes the exhaust is definitely sorted, but the droning noise hasn't gone.  And in another thread one poster suggests that might be a worn bearing around the mid-point of the drive shaft.  I mentioned this to a knowledgeable independent garage who said yes it's possible but he wasn't so sure as I'm not getting any wobbling of the car.  And the droning noise has been there for a couple of years without getting any worse.  Could a bearing last that long if it was failing?

I think I'm getting a bit fussy .... this car is amazing for 172k miles 😄

Mike

[Bluemarlin]

3 hours ago, mikesands said:

well ......  yes the exhaust is definitely sorted, but the droning noise hasn't gone.  And in another thread one poster suggests that might be a worn bearing around the mid-point of the drive shaft.  I mentioned this to a knowledgeable independent garage who said yes it's possible but he wasn't so sure as I'm not getting any wobbling of the car.  And the droning noise has been there for a couple of years without getting any worse.  Could a bearing last that long if it was failing?

I think I'm getting a bit fussy .... this car is amazing for 172k miles 😄

Mike

Hard to say whether it's an issue or you're being fussy, without knowing how loud it is.

That said, if it doesn't appear to be causing any problems after a couple of years, and the mechanic says there's no problem, then at 172k miles I'd  be tempted to just turn the music up and enjoy the ride 🙂

[steve2006]

The above post reminded me of a workmate in the 70s who at the time had a Riley Elf.

On hearing a squeaking noise he did turn up his radio but very shortly afterwards the car suddenly dropped on the front driver’s side and ground to a halt as his front wheel continued at pace down the road 😀