Fault for this month: an Oil Cooler Leak

Delphius1 · September 19, 2018

This car seems to be throwing up a problem a month at the moment. Here's the latest:

Noticed a wet patch on the nearside valance under the bumper this week. Released it to have a look and there's an oil leak from the oil cooler loop just behind the bumper.

Lexus want £71 for one, so that'll have to wait until pay day! I might have a word with my local Toyota garage like I did with the LED brake lamp and see if the price is any different.

Here's what mine looks like currently:

At least if it soaks the mounting bolts in ATF they should be easier to remove when I actually get around to getting one. While I'm under there I might drill and tap the bolt holes for the valance mounting bolts that have sheared.

In other news fuel consumption has suddenly dropped by 10mpg since a trip up North and back. No error messages on the OBD2 so I suspect one or more suspension bushes have gone while I was hooning (as much as one can hoon in an RX300) around the twisty roads. I'm currently looking for Polyurethane replacements for the front arms. The rear bushes look very tired.

This car just wants to keep me busy!

Britprius · September 19, 2018

Not having much luck with this one Mark, but it will keep you out of mischief over the weekend. Do those pipes run in the radiator if so I hope they come out cleanly for you, and that the rad it's self is sound as I know on some models they are troublesome.

John.

The-Acre · September 19, 2018

Can't the pipe be replaced with copper microbore like some do with the LS power steering?

ColinBarber · September 19, 2018

2 hours ago, The-Acre said:

Can't the pipe be replaced with copper microbore like some do with the LS power steering?

I'm sure it would work but copper isn't really strong enough for the constant vibration and potential for impact from stones etc. It's one thing to lose power steering if you spring a leak but to quite another for your transmission to run dry and be damaged.

welland · September 19, 2018

4 hours ago, Delphius1 said:

In other news fuel consumption has suddenly dropped by 10mpg since a trip up North and back. No error messages on the OBD2 so I suspect one or more suspension bushes have gone while I was hooning (as much as one can hoon in an RX300) around the twisty roads. I'm currently looking for Polyurethane replacements for the front arms. The rear bushes look very tired.

Surprised that suspension bushes could cause any loss in mpg, let alone 10mpg.

The-Acre · September 19, 2018

1 hour ago, ColinBarber said:

I'm sure it would work but copper isn't really strong enough for the constant vibration and potential for impact from stones etc. It's one thing to lose power steering if you spring a leak but to quite another for your transmission to run dry and be damaged.

I thought that copper being soft would be able to cope with the odd stone hitting it.

ColinBarber · September 19, 2018

it's quite thin though, doesn't take much to puncture it - certainly not the domestic kind.

The-Acre · September 19, 2018

1 hour ago, ColinBarber said:

it's quite thin though, doesn't take much to puncture it - certainly not the domestic kind.

I understand what you're saying, but as someone who has done plumbing for many years I think it's up to the job. The reason I mention it being soft (although not that soft) is that it can absorb a bit of a hit without breaking or puncturing. If it was mine I'd certainly do it and feel confident that it would last.

Delphius1 · September 20, 2018

Guys, thanks for the suggestions and the sympathy.

Luckily the oil cooler is stand-alone so no real issues with replacing it other than I'll probably swap the sorry-looking springy hose clips for jubilee clips.

I did think of copper pipe, but I'm not sure if there would be a bad reaction to the copper. I'm probably going to find some steel pipe of the same bore and then use it as a link to a rubber hose and just make a loop of rubber hose for now. It's not like the weather is going to be hot and the car does have the oil cooler in the nearside wheel arch, so that can do the cooling until I get a replacement steel pipe. Which will be coated to make it last longer! Looking on eBay you can get a couple of "proper" motorcycle oil coolers for less than the Lexus bent steel pipe!

As for the MPG, my gut instinct is front wheel alignment as the offside front tyre has that shiny appearance on the inside you get when it wears a bit too much. Also when you take your foot off the throttle there is a perceptible drag and the car slows down more than it used to. Only happened after my run over the Snake pass and back, I've jacked it up and the brakes don't bind and no fault codes on the OBD so the logical thing is alignment.

Being a big old barge they are hard on bushes, so polyurethane may be the way to go. The rear bushes on the front arm are available in the uk, but the front bushes may be difficult to source. I know powerflex do them but I've not seen the RX on any supplier lists.

Looking on t'internet the front bush for the front lower arm might be a pain to replace. I have heard mention of dropping the subframe in order to undo the bolts. I hope that's not the case, I would really like it to be easy and be able to do it myself rather than pay someone. :-)

Of course after it's done it will need wheel alignment as well. <gets ready to apply fire extinguisher to wallet...>

UPDATE: Found this video on youtube, the engine mounts need removing to get at the front bushes, so the subframe doesn't need dropping, but the engine does need propping up while you do it:

Gliderpilot · September 20, 2018

Done this job on my 400h and it's not easy but if you look in the online maintenance manual lexus copy the first line is remove the engine and transmission!!!!! I just managed to do it with a great deal of difficulty by jacking up the engine, but it wasn't easy at all.

Delphius1 · September 25, 2018

Here's an update. The oil cooler leak got worse, so I've used microbore copper pipe to join the two rubber hoses together temporarily. So far everything ok. Had to cut the hoses off the oil cooler because the "ears" on the spring clips disintegrated when i tried to release the clips.

I suspect the rusty tube isn't actually an oil cooler, but is really there to allow the transmission cooling hoses to be easily joined to the rad when the car is being assembled and the power train mated to the body. As the car already has the arch-mounted "proper" atf oil cooler in the transmission cooling line the steel tube thing seems superfluous.

At 70-odd quid, I've decided to bypass it and just buy a metre of oil cooler hose. I'll run new hoses between the rad, proper oil cooler and auto box. Space is tight, so it may be a bit difficult and knuckles will be skinned. But I'm saving oodles of money that is going into the suspension bush issue.

I've ordered polyurethane SuperPro bushes from these chaps: https://www.japanese4x4spares.co.uk/ They don't keep bushes for the RX in stock but Rob, the nice chap on the phone said as they are a SuperPro distributor they could get them in and sent out to me. Hopefully within 10 days.

SuperPro are the only company I can see that does the front and the rear bushes for the front arms in Polyurethane for the RX300.

The bushes came to over £100 with postage, but far better than £300 for replacement arms with rubber bushes. Fitting isn't going to be easy with the aformentioned difficulties, but I may have a cheap way round that. Then there's getting the wheel alignment done. I'm looking forward to seeing how much improvement there is in the steering and handling front. Hopefully it will steer round corners when I want it to and not half a second later. :-)

More updates to follow as I get the jobs done.

Gliderpilot · September 25, 2018

Cost me £150 for arms and ball joints from eBay.

Jaystar77 · September 25, 2018

I installed an aftermarket oil cooler for the transmission on my Starlet a few years back (I know what you're thinking but same basic principle as these big buses 😁) think it cost around £40 and bypassed using the engine radiator. Bought the bits off American eBay and it worked fine. You pretty much just mount the cooler to the radiator core so as it sees airflow.

Probably a bit overkill but thought I'd throw in the option!

Jaystar77 · September 25, 2018

Okay found a pic to show what I mean, due to fitting a bigger turbo I had to upgrade from the stock rad (black) to a smaller rad (silver) and so added a separate ATF cooler (funky thing in the bottom right). TBH it was a little big for the application but the autobox seemed to be quite happy all the same. Also gave me a slightly bigger oil circuit to play with.

You could slap a similar core onto the RX whilst you are playing with pipes.

ColinBarber · September 25, 2018

The European RXs already have an separate oil cooler at the front of the wheel arch, and the normal cooler inside bottom of the radiator.

Delphius1 · September 25, 2018

Yep, the oil cooler is sat in the L/H wing in front of the wheel arch and the transmission oil also goes through the radiator, so there's plenty of cooling without the steel tubes behind the bumper. Hence why I'm convinced the steel tubes aren't really an oil cooler (even though that's what Lexus call it on their diagrams) but a device to make assembly easier.

I'll see how things go with it bypassed.

ColinBarber · September 26, 2018

On the series I, and possibly series II, the US models didn't have the separate cooler in the wing so maybe the extra piping is used as a poor mans cooler for vehicles that don't have a real one.

Delphius1 · September 26, 2018

There's still the radiator cooler even on the earlier models which is usually sufficient. I'm sure some time and motion study at Toyota decided it was cheaper to fabricate two pipes and bolt them to the front valance and pay a guy for 20 seconds to join the autobox hoses to the pipes with easy access. Otherwise it's pay him anywhere between 2-5 minutes as he furtles about plugging the pipes into the radiator or auto box directly with very little space to work in.

That's a long way down the assembly track getting in the way of all the other assembly workers and delaying other parts being fitted and running up costs... :-)