Rx400h Rattle (not Interior)

rog99 · July 23, 2015

Hello

My RX has two rattles, which are only (really) noticeable when the windows are open, so i'm fairly sure it's outside (or under the bonnet).

I've done a search, and most/all of the threads I found were about speaking rear seats (got that too!) or creaking dash (not got that, thankfully).

I have had a look under the car and tugged at anything I could get a gloved hand on, and nothing seems obviously loose.

The rattle is noticeable at low speeds (eg when crawling on battery) and even small bumps in the road seem to cause it. The noise sounds like a loose cover or something - it is a tinny metal-metal or metal-plastic noise, rather than a clunk. Only audible with the window open.

(may also rattle when at higher speeds, but I don't have the windows open then)

I have noticed when the engine starts, there is a similar (but maybe different?) rattle from under the bonnet. Car has had 100k service recently (at Lexus) and everything checked out, so I don't think this signifies an issue with the engine itself (both the 'engine starting' rattle and the 'slow speed maybe something else rattle' were both there pre-service, and afterwards). The engine-starting rattle is 'just' audible with the windows up, but louder than the other low speed rattle.

So, any ideas what I should be checking specifically? Either under the car, spare wheel, or under the bonnet (as I know these sounds travel and are often not where you first suspect).

Photos or lengthy descriptions would be a plus, if possible.

It seems such a shame to waft around in quiet comfort inside the car, but to everyone outside it sounds like bits are falling apart!

Thank you.

ChrisKaye · July 24, 2015

Sounds like exhaust heat shield to me!

It's on the top of the engine right at the fron of the car near the radiator.

Mine does the same but only when engine is cold and idling.

If this is the case with you, then you might be able to fix (per another member's idea) by putting a couple of large washers either side of the heat shield fixing bolt that looks rusty/corroded....

If you have bonnet open and get someone else to start the engine when cold, you should be able to test this by holding the heat shield when the rattle begins! Make sure it's cold tho!

mikesands · July 25, 2015

Roger - I could have written that first post myself today. Mine too has recently had a 100k service and there's now this tinkling metallic sort of rattle. Don't think it was there though immediately after the 100k.

Mike

tom123 · July 26, 2015

I had a similar sounding rattle that turned out to be a loose bonnet/hood catch.

rog99 · August 23, 2015

OK, time for an update.

I took the bolt off what I believe is the heat shield in the engine bay - the vertical bolt just behind the radiator. I added a chunky washer I had lying around (from a recently extinct washing machine) and re-did the bolt. This has improved/reduced the 'engine starting rattle' a little, but not eliminated it fully.

I have discovered that the 'external rattle' is something to do with the front brakes, as when going down hill the other day with the windows down (short journey, at low speeds (30-40) so seemed pointless using the aircon) I realised that the rattle stops while the brakes are gently applied. Haven't had chance to investigate this one further, but recall seeing another post about rattling brakes on here a while ago, so will track that down for starters and see what the fix was.