rickam

Hello everyone. I'm having a tough morning because the lady of the house was warming up the RX450h this morning in the driveway. It's -14 celsius (6 F), so pretty cold but nothing extreme. So what I hear is the engine running, but a loud hissing sound coming from under the hood and this sort of sound of sand (That's the best way I can describe it). So I tell her to switch of the engine straight away. I then have a think, then scan the car for DTC's and it's showing an engine low power output code for the IC engine.

I start the engine again and I can see the exhaust blowing from inside the engine compartment, and also at the joint from the manifold before the Catalytic converter and no exhaust coming from the tail pipe so it looks blocked. My first instinct was to look at the tailpipe for a potato wishing someone was playing a prank on us, but no such luck! I've just come inside to warm up and I'm just shaking off those initial feelings of dread, but I have read that the RX450h has something called a "exhaust heat recovery system" so it looks like I have a lot to learn before I tackle this problem.

Some background information:
-The battery was very weak several days ago because the dome lights had been left on for several days. I had read that they would switch off automatically, but it was enough to run down the battery and the car would not start, so I put on a NOCO smart charger and the battery is still fully charged and OK (about 12 months old, original Panasonic from dealership).
-I started the car last night and let the engine run for about 20 minutes without issue.

Possible causes that I can think of:
-Something is frozen. possibly an exhaust solenoid valve etc? But then how could it be possible for the exhaust to be fully blocked without some kind of fail-safe or bypass engineered into the system?
-Did I dislodge some carbon buildup in the system when I slammed shut the hood, or am I being paranoid?
-Mice chewed wiring to the EGR or exhaust heat recover system last night?
-The ECU lost the plot when the battery was weak and in a brownout condition. Should I pull the fuses for the ECU and EFI? If this is the case, why did the car run last night.

I'm at a loss. It's wishful thinking that the problem will clear up as mysteriously as it appeared, but if anyone has had a similar issue or know if I have to run any adaptations in Techstream after a battery has failed please let me know. In all my days, I've never seen a car do something like this. Any input or ideas are very welcome.

Clutchless

It is probably related to the cold, but it may be a clogged catalytic converter.
It helps us diagnose these questions if you provide the model year and mileage on your vehicle and whether it is still under some of the warranty. However, Canada probably has different warranties than the US.

rickam

Thanks Clutchless. Thank you for very much for that suggestion, I'm actually looking into clogged catalytic converters right now. That seems to be the only thing after the manifold unless there is some special equipment on the RX450 that other cars don't have from the manifold onward. I'm very new to this vehicle so I have a lot to learn. i've just googled how long a cat lasts and its showing on average 70-100K

The car is a 2010 RX450h. Our mileage is about 80,000

I'm going to make a coffee and think about cutting out the old cat to have a look inside. It could very well have been the cold that put in the last nail...

Hayk

iTrader: (1)

Catalytic converters last a lot longer than 100k on Lexus but they can fail prematurely.

The next step would be to remove the Oxygen sensor from that manifold and take a look inside the pipe with a small inspection camera.

A mechanic should also have a pressure gauge to measure the exhaust back pressure at that hole. If it exceeds a certain amount, you’ll need a new exhaust pipe for that section. Probably around $1500-2000, but I haven’t checked the parts for that car.

rickam

Good tip on the inspection camera and the pressure gauge. What I'm thinking of doing is dropping the whole middle section of the exhaust and welding in a replacement Catalytic converter just ahead of heat-exchanger. Once I get it off I should be able to see into the cat clearly and confirm that it is blocked. I even considered just welding in a straight section and omitting the cat as the car has two other cats and will still have less emissions than most of the cars in the area. I've looked at the cost of replacement and it's beyond expensive, possibly even enough to write off the car if I take it to the dealership.

At the moment I'm exploring the failure modes of the heat-exchanger on the exhaust mid-section just to clear my head of any other possibilities. From what I've read it will fail open or shut to the coolant flow. If it fails open then your car will overheat, fails closed and probably not a problem but I imagine that there would never be a failure mode that would ever block the exhaust? Also I don't think there are any oxygen sensors past the first two manifold catalytic converters, or electronics in the heat-exchanger to worry about unless anyone knows otherwise. If so, please let me know!

P.S. I had read on the net that someone with an RX450h nearly lost their lower catalytic converter to thieves but comically they cut into the coolant line on the heat-exchanger and decided to give up when they where then covered in 10 Liters of coolant.

salimshah

IMHO you are overthinking the problem. It is just a plumbing issue.

Heat exchanger/recovery is nothing that should prevent the free flow of exhaust. Check you coolant level and then move on to other areas.[I too need to learn and confirm that the coolant is heated up with exhaust]

Exhaust is modular .. working from tail end ... muffler(resonator), 2nd cat, 1st cat(Warm up cat), engine exhaust port ... with oxygen sensors and heat recovery (if equipped) in between. All these are connected with tubes and have flanges. Just disassemble the flange to see free flowing exhaust. Granted the engine is fixed end (immoveable), but the whole exhaust is on flexible hangers.
Remember to replace the gaskets as they should not be re-used. Felpro is a good brand, if you want to save some $$.

Salim

Droid13

I agree on this. Trouble with the heat exchanger means coolant all over the place. It would not block exhaust as its only symptom. Move on.

CanJim

I seem to have the same frozen exhaust problem. 2015 RX450H. It sounded like a steam engine and then cut out. Currently at the dealer where they say they've not seen this before.

They have it until Tuesday because of the long weekend, they want to let it melt and then drop the exhaust to drain it. What should I be telling them to check, the coolant system around the heat exchanger?

Glad I found this thread, misery loves company.

rickam

Hi CanJim, that's so funny because I came to the same conclusion this morning after thinking about it some more, and reading over the Borg Warner patents on exhaust heat recovery systems. I then read a bunch of threads on the net about various car makes including VW and some others, and it seems that the exhaust icing over is not so uncommon after all. Some people have even drilled small holes and either put in a screw afterwards, or filled them in by welding or with Gun-Gum (what they use in the UK), or similar. What I've done is got out an old rope-light (NON LED VERSION), and wraped it around the length of the exhaust, and then covered that with silver bubble-wrap from home depot, but I guess some old wool blankets could work also. I feel better doing it this way than using a torch or a butane backpacking stove. Or if you have a garage available, switch the car to electric only mode and you can drive it in there to thaw.

After what Clutchless and Hayk have sai, I believe my testing the car the night before is probably what blocked the exhaust. I would have been better off giving it an extended warm-up on the morning the car was to be used. My feeling is that the heat-exchanger was probably robbing the exhaust of heat but not moisture and when that cold damp air hit the muffler it just settled down and froze. The following morning it completely froze over after a couple of minutes. So this problem can happen to any car, but I'm wondering if that heat-exchanger made things worse as I've never personally experienced it in all my days. Do later RX450 models have this part installed? I guess in the right conditions anything can go wrong. Many passenger planes have had well designed sensors ice over, and there was even a case where they designed an jet fuel pre-heater to make an engine safer, but it actually trapped ice crystals and caused the plane to crash (that along with an auto-pilot system that would not allow the crew to ease off the throttle to allow those crystals to melt).

CanJim. I'm in Toronto, do you think our cars faced the same weather system (complicated by Covid driving habits)? All best and thanks everyone!

ColAngus

80,000km or miles?
I don't believe there's a blockage. It's really not that cold. It's been -30 at night in Alberta for over a week. Your muffler will already have a drain hole for water, anyway.
I believe you have an exhaust leak, likely a manifold gasket but possibly a joint near the front.

CanJim

I thought I'd given the car a good run last Monday, maybe half an hour. I can't remember if I parked on the street for a while before putting it in the driveway. I agree it's not that cold but maybe combined with the short run having left moisture in the system it was enough. I wonder if anyone knows of any damage this might have done to the exhaust system.

I wondered about a manifold gasket because of the chuffing noise it made.

CanJim

It's back from the dealer who kept it over the long weekend to thaw it out. They then removed the exhaust and emptied out. Appears to have been an accumulation of condensation because I don't drive it much. I have to do highway blasts to clean it out in future. I'm sure the police will be quite understanding. So it's back on the road albeit an icey road.

Thanks for the advice and support.