peafarmer

Hi, I just has a problem with my 2003 LS430, 230K miles. I had the EFI 2 fuse blow which caused a bunch of error codes and put the car in limp mode. I found the problem to be the heat shield on the exhaust manifold which encircles the upstream driver side O2 sensor. There is a similar heat shield on the passenger side. The heat shield is normally held by a bolt / screw on the top side of the flange upstream of the catalytic converter. Heat had caused the shield to come off and it was being held in suspension by the bank 1 sensor 1 O2 sensor wires. This caused a short in the O2 sensor heater wires, which caused the fuse to blow.

Anyway, I know how to solve the problem with the O2 sensor and fix the blown fuse, but I am wondering if I need to somehow re-install this heat shield. The one on the passenger side is getting ready to let go as well. I am wondering if this shield is needed to prevent failure of the O2 sensor due to heat. I can see that the shield would definitely keep some heat off those sensors, but are the shields overkill?

If anybody has any experience with it I would appreciate your input.

Thanks
Andy

Juggis80

I have exactly the same issue with those front O2 sensor heat shields. Shields have come loose and are dangling on the O2 sensor wires. Should I try to fix them somehow or should I cut them off? Any input is appreciated.

Striker223

Replace them

911LE

Replace them or install thermal insulation to the exposed part of the sensors and the wiring. Something made for spark plug wires would work. DEI makes a few products that would suffice.

YODAONE

The LS400 exhaust manifolds did not use collar shields around the oxygen sensors as did the LS430.

Toyota spent money on this extra part for a reason...possibly the wiring was frying.

However, this shield appears to be sold as part of the exhaust manifold assembly but not as an autonomous part number.


The smaller oxygen sensor shield is barely depicted at inside of manifold elbow just above flange...


I have a set of very good condition exhaust manifolds from a low mileage LS430.

P.M. me as to your interest.

StanVanDam

I reported engine block squeaking while the engine was off to my local Lexus dealership a few weeks ago, been ongoing for the past 2+ years. They identified the problem as loose front O2 sensor heat shields and I guess they were confident enough in that because they didn't ask if I wanted them cut off or replaced or anything, they just went ahead and cut them off. It did indeed eliminate the noise.

Lexus dealership did not mention any adverse effects of removing these heat shields. I've just finished a 2200km roadtrip, many hours of continuous driving with no O2 sensor wires melted and no dead O2 sensors, yet. I'll report back if the lack of these shields causes a problem.

YODAONE

I have a pair of LS430 Exhaust manifolds left over from LS430 (3UZ-FE) engine transplant into LS400.

The LS400 exhaust manifolds and shields were professionally coated with ceramic heat barrier by Jet-Hot..so heat is better retained within tubes.

The dealer knew the failed heat shields are not sold separately, so rather than charge for new exhaust manifolds at $400 each and labor $$$, or fabricate a new shield in order to effect correct OEM repair, they punted.

The ECU reads "data" received from the oxygen sensors and at several hundred degree Fahrenheit, there is going to be increased resistance and voltage drop, depending on conditions...and the ECU required most accurate data to do perform.
LS430 ECU resides in engine compartment..not a fan of placing electronics in a hot engine bay...so the heat shield(s) subdue temperature spikes.

With the electric fan scheme, at times there is zero circulation so if not moving, things in pockets start to cook.

bradland

This is the smartest solution. It makes no sense to replace an entire exhaust manifold just to acquire a small uncompromised heat shield which is nothing more than precautionary insurance.

05ls430518

iTrader: (1)

I ran my car with stainless uncoated PPE headers for a year and there was no issue with it melting the o2 sensor wires or anything else. If you take the shields off nothing bad will happen to the sensors, as long as you are not getting things red hot in the engine bay you will be fine.

YODAONE

Wonder why Toyota would spend engineering time, labor and materials in production of heat shields.....

Here is my answer:

https://www.clublexus.com/forums/ls-...-coatings.html

Striker223

The 430 ECU has a cooling duct routed to the front of the car that when moving cycles cooler air around it and the other modules in the casing. I'm not certain but I think the engine fans also allow some air to move into the duct at idle as well.

05ls430518

iTrader: (1)

Ok and? the op asked if it was ok to take the heat shields off without damaging anything so thanks for your lecture but no thanks I am gonna pass on reading it have a wonderful day.

05ls430518

iTrader: (1)

You are 100% correct the ecu and fuse panel are getting "cold" air even when the car is at a stop idling.

Juggis80

Well, after 5 years of driving without O2 sensor heat shields everything is still fine.