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1uz-fe Interference Engine


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Hi guys, I am posting this for a friend of mine. Here is the story: 93 Lexus SC400- Water pump broke and took out the timing belt. He called me I went to his house pulled the timing cover off and varafied that the belt was in fact broken. I told him to take to a Toyota/Lexus specialty shop to have the timing belt and water pump replaced. He ended up taking it to a general automotive repair facility not specializing in Toyota or Lexus, a "Jack of all Trades" type of place. The shop replaced the timing belt and water pump and called him and said that there are 3 cylinders that have no compression because of the pistons hitting the stuck open valves. This struck me as odd. I am no stranger to working on Toyotas and in my past experences I have never seen a belt driven Toyota or Lexus bend any valves in the event of a timing belt breaking. They are trying to sell him a whole new engine in the sum of about $5,000.

I have searched all over the web and this website and the overall concensus is that the 1UZ-FE is a non-interference engine. But even with an overwealming majority saying it will not interfere there is still some people who claim it will interfere, but they don't seem to have anything to back up their claims.

I would like people to post their experences with timing belt breakage. I really would like to hear of at least someone that had the valves bend. Personally I think interference on a 1UZ-FE is impossible and the mechanics are clueless or they are trying to take advantage of my friend. Can anyone tell me with 100% certanty if it is possible? I appreciate the help!

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My timing belt on my 92 SC400 broke last month. I didn't take it to a specialty shop, but I told them what I was told (from this forum) that the 1UZ-FE was a non-interference motor. Anyway, the timing belt was replaced along with my water pump. Car started up with no problems. They didn't check the compression on the cylinders though. They did tell me their manual shows the 1UZ-FE as an interference motor.

Hi guys, I am posting this for a friend of mine. Here is the story: 93 Lexus SC400- Water pump broke and took out the timing belt. He called me I went to his house pulled the timing cover off and varafied that the belt was in fact broken. I told him to take to a Toyota/Lexus specialty shop to have the timing belt and water pump replaced. He ended up taking it to a general automotive repair facility not specializing in Toyota or Lexus, a "Jack of all Trades" type of place. The shop replaced the timing belt and water pump and called him and said that there are 3 cylinders that have no compression because of the pistons hitting the stuck open valves. This struck me as odd. I am no stranger to working on Toyotas and in my past experences I have never seen a belt driven Toyota or Lexus bend any valves in the event of a timing belt breaking. They are trying to sell him a whole new engine in the sum of about $5,000.

I have searched all over the web and this website and the overall concensus is that the 1UZ-FE is a non-interference engine. But even with an overwealming majority saying it will not interfere there is still some people who claim it will interfere, but they don't seem to have anything to back up their claims.

I would like people to post their experences with timing belt breakage. I really would like to hear of at least someone that had the valves bend. Personally I think interference on a 1UZ-FE is impossible and the mechanics are clueless or they are trying to take advantage of my friend. Can anyone tell me with 100% certanty if it is possible? I appreciate the help!

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Looks like the 98 model SC400 went to interference looking at this info.

1992 Model

Introduction of Lexus SC400

SC400 4.0-liter (242 cubic inches.), four-cam, 32-valve 90° V8

Horsepower at rpm, 250 hp @ 5,600 rpm.

Torque at rpm 260 lb-ft @ 4,400 rpm.

0-60 mph acceleration 6.9 seconds.

1/4-mile acceleration 15.3 seconds.

Top track speed 150 mph.

Fuel consumption 18/22 mpg City/Highway.

Aerodynamic drag coefficient 0.32 ,0.31 with opt. rear spoiler

4-Speed automatic Electronically Controlled Transmission with intelligence (4ECT-i), with power/normal shift modes. Rear-wheel drive (optional Traction Control System).

4-wheel independent, double-wishbone suspension.

Vehicle speed-sensing, progressive power rack-and-pinion.

4-wheel ventilated, power-assisted anti-lock discs (ABS).

1993 Model

Passenger airbag SRS added.

New Lexus Portable Plus Cellular Phone option.

Automatic headlamps added.

All outboard passenger seatbelts now include "ALR" function that allows easier use of a child seat (without a locking clip).

New exterior colour: Graphite Metallic.

1994 Model

Instrument panel illumination changed from white to amber.

Climate control system revised for CFC-free refrigerant.

New emissions controls and on-board diagnostics.

Revised stitching on leather-wrapped steering wheel.

Thicker steering wheel rim.

1995 Model

Revised front air dam; extension deleted.

Revised tail lamps.

New wheel design.

Cornering lamps replaced with foglamps.

Audible remote entry.

Revised power passenger seat.

Parking brake handle moved 0.4-inch farther away from driver's seat.

Climate control and audio system displays changed from green to amber.

Outside temperature gauge added.

Second cupholder added.

Revised audio system.

Meets 1997 side impact standards.

Slight suspension and steering retuning.

New noise-control measures added.

Ivory instrument panel changes hue.

New interior-trim colours: Black Leather replaces Gray Leather

New exterior colours: Renaissance Red, Platinum Silver Metallic and Teal Mist Metallic.

1996 Model

Engine still is a 32-Valve V8, but power uprated to 260 hp.

Horsepower at rpm, 260 hp @ 5,300.

Torque at rpm, 270 lb-ft @ 4,500.

0 - 60 mph acceleration 6.8 seconds.

1/4-mile acceleration 15.3 seconds.

Top track speed 149 mph.

Meets 1997 federal side-impact standards.

Multifunction remote entry system with audible signal, car finder, trunk release and "panic mode".

Rear-window glass-imprinted antenna.

Pre-tensioners added to front seatbelts

Adoption of electrochromic mirrors

Moonroof adoption of one-touch open slide function.

Lexus chrome-plated wheels.

Exterior colour discontinued: Teal Mist Metallic.

Exterior colour addition: Bordeaux Pearl.

1997 Model

Flush foglamps.

New upper/lower grille.

Color-keyed side skirts.

Redesigned rear spoiler, bumper and taillamps.

New alloy wheel design.

Exterior colour discontinued: Sandstone Beige Metallic, Royal Jade Pearl and Midnight Indigo Pearl

New exterior colours: Shadow Rose Quartz, Classic Green Pearl and Royal Sapphire.

1998 Model

New engine with continuously Variable Valve Timing with intelligence (VVT-i).

Horsepower at rpm, 290 hp @ 6,000.

Torque at rpm, 300 lb-ft @ 4,000.

0 - 60 mph acceleration 6.3 seconds.

1/4-mile acceleration 14.7 seconds.

Top track speed 149 mph.

Fuel consumption 19/25 mpg city/highway.

Aerodynamic drag coefficient 0.32 (0.31 with optional rear spoiler).

New five-speed Electronically Controlled Transmission with intelligence (ECT-i).

Five-speed automatic Electronically Controlled Transmission with intelligence (ECT-i). Overdrive fifth gear, auto-select shift program, engine/transmission networking, flex-lockup torque converter

Improved tires.

Genuine wood trim on the center console.

Electronic programmable garage-door opener.

Gated shifter and wood- and leather-trimmed shift knob.

Adoption of in-key multifunction remote.

Vehicle theft-deterrent and immobilizer system, with in-key transponder.

New exterior colors: Imperial Jade Mica and Baroque Red Metallic

1999 Model

Automatic Sound Levelizer (ASL).

Adoption of Digital Sound Processor.

Six-disc CD auto-changer standardized.

Floor mats standardized.

Three-spoke steering-wheel design.

Daytime running lights.

Larger brake size.

SC 400 V8 engine meets Transitional Low-Emission Vehicle (T-LEV) certification for 50 states.

New exterior colors: Golden Pearl, Millennium Silver Metallic and Angora Beige Metallic.

2000 Model

On-board Refueling Vapor Recovery (ORVR) system.

Exterior colour discontinued: Baroque Red Metallic.

Exterior colour addition: Cinnabar Pearl.

New Model introduced for 2001

SC430

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Hi guys, I am posting this for a friend of mine. Here is the story: 93 Lexus SC400- Water pump broke and took out the timing belt. He called me I went to his house pulled the timing cover off and varafied that the belt was in fact broken. I told him to take to a Toyota/Lexus specialty shop to have the timing belt and water pump replaced. He ended up taking it to a general automotive repair facility not specializing in Toyota or Lexus, a "Jack of all Trades" type of place. The shop replaced the timing belt and water pump and called him and said that there are 3 cylinders that have no compression because of the pistons hitting the stuck open valves. This struck me as odd. I am no stranger to working on Toyotas and in my past experences I have never seen a belt driven Toyota or Lexus bend any valves in the event of a timing belt breaking. They are trying to sell him a whole new engine in the sum of about $5,000.

I have searched all over the web and this website and the overall concensus is that the 1UZ-FE is a non-interference engine. But even with an overwealming majority saying it will not interfere there is still some people who claim it will interfere, but they don't seem to have anything to back up their claims.

I would like people to post their experences with timing belt breakage. I really would like to hear of at least someone that had the valves bend. Personally I think interference on a 1UZ-FE is impossible and the mechanics are clueless or they are trying to take advantage of my friend. Can anyone tell me with 100% certanty if it is possible? I appreciate the help!

The 92 - 94 Is a NON-Interference engine..I think only the 95 - 97 are Interference engines..if he was told the 92 is..then he is flat down right lying...!!!!

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Hi guys, I am posting this for a friend of mine. Here is the story: 93 Lexus SC400- Water pump broke and took out the timing belt. He called me I went to his house pulled the timing cover off and varafied that the belt was in fact broken. I told him to take to a Toyota/Lexus specialty shop to have the timing belt and water pump replaced. He ended up taking it to a general automotive repair facility not specializing in Toyota or Lexus, a "Jack of all Trades" type of place. The shop replaced the timing belt and water pump and called him and said that there are 3 cylinders that have no compression because of the pistons hitting the stuck open valves. This struck me as odd. I am no stranger to working on Toyotas and in my past experences I have never seen a belt driven Toyota or Lexus bend any valves in the event of a timing belt breaking. They are trying to sell him a whole new engine in the sum of about $5,000.

I have searched all over the web and this website and the overall concensus is that the 1UZ-FE is a non-interference engine. But even with an overwealming majority saying it will not interfere there is still some people who claim it will interfere, but they don't seem to have anything to back up their claims.

I would like people to post their experences with timing belt breakage. I really would like to hear of at least someone that had the valves bend. Personally I think interference on a 1UZ-FE is impossible and the mechanics are clueless or they are trying to take advantage of my friend. Can anyone tell me with 100% certanty if it is possible? I appreciate the help!

The 92 - 94 Is a NON-Interference engine..I think only the 95 - 97 are Interference engines..if he was told the 92 is..then he is flat down right lying...!!!!

I thought it was '98 and up that were interfering as thats when VVT-i was made onto the 4.0L V8's? We really do need to get this clarified as i had a similar topic for my '92 SC400 as the mechanic at my local lexus dealership said that the '92 is "Definitly an interference motor," but everyone on here says that it wasnt till VVT-i was added ('98 and up) that the engine became interference. Someone please clarify this once and for all!!!

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Well, a little update for everyone. I called an old buddy of mine who is a Toyota/Lexus Master Diagnostic Technician. He told me that the 1UZ-FE was one of the only belt driven Toyota engines that ARE interference. He said he has seen a few that have hit the valves. He also said that for whatever reason it is more common for them to not interfere. I have known this guy for years and I trust him. But I would still like to hear from someone that has had it happen to them personally.

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I am with you I keep reading and reading but so many are not matching stories cannot tell any more I have a 96 and the last owner told me that it was changed at 115000 but I can't tell but if someone could really tell me if mine is or is not I would really appreciate that info.

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  • 4 months later...
simple , no vvt no interference.

It may in fact have lost compression but it is not because the valves hit the pistons.

Thanks, really appreciate the correct info..

Hi Guys,

here is brochure list, that says that lexus is non interference engine. even after 98

Check it out

So no way you can loose a valve . B)

Best

428_1466_web.pdf

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  • 5 years later...

What I have learned by looking at this Gates Timing Belt Guide Book...

http://us.lexusownersclub.com/forums/index.php?app=core&module=attach&section=attach&attach_id=9725

People say that the 1990 to 94 are non interference, and everything after that is interference. Well, after doing some research that is partially true. The 1990 to 1997 actually has the same exact engine called 1UZ-FE. Also uses the same timing belt part number as well. That engine seems to be non-interference. However, the 1998 to 2000 are called 1UZFE. Notice there is NO dash between z and f. The 98 to 2000 is a completely different engine as far as valvetrain. So, the username, " eds92sc," has mentioned about the 1998 model LS and SC400 motor vehicles receiving a new engine with continuously Variable Valve Timing with intelligence (VVT-i), this is the 1UZFE interference engine. I hope I was able to shed some light on this matter.

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What I have learned by looking at this Gates Timing Belt Guide Book...

http://us.lexusownersclub.com/forums/index.php?app=core&module=attach&section=attach&attach_id=9725

People say that the 1990 to 94 are non interference, and everything after that is interference. Well, after doing some research that is partially true. The 1990 to 1997 actually has the same exact engine called 1UZ-FE. Also uses the same timing belt part number as well. That engine seems to be non-interference. However, the 1998 to 2000 are called 1UZFE. Notice there is NO dash between z and f. The 98 to 2000 is a completely different engine as far as valvetrain. So, the username, " eds92sc," has mentioned about the 1998 model LS and SC400 motor vehicles receiving a new engine with continuously Variable Valve Timing with intelligence (VVT-i), this is the 1UZFE interference engine. I hope I was able to shed some light on this matter.

Unfortunately the Gates manual you referenced has numerous obvious errors but at least it is more accurate than older versions.

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  • 2 months later...

Well, I'm not at all sure how this comes out.

I just purchased a 1993 sc400 with 206,000 miles. The last verified timing belt change was at 89.500 - both on the sticker in the engine bay and in the service list at Lexus.com. (Many thanks to the member who posted that link.)

I guess the prudent thing is to not take a chance and have the AAA bring it home so that I can change the belt. Just doesn't seem worth the risk of ruined engine. However, while I have it "open" I'll hand turn the crankshaft through two complete revolutions and see if I encounter any resistance. I'll post the results.

Won't be absolutely definitive, since if a belt breaks at high rpm, there might be valve float that would jam valve or hole a piston.

Needs a water pump, too. That's defninitely leaking.

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You will want to change the water pump, idlers, tensioner and a few other misc. parts besides the belt. The water pump on a 90 LS400 I bought new seized at only 75,000 miles and trashed the timing belt. I had very little warning ... smelled coolant ... lost power and coasted into a convenience store parking lot - lucky I was not yet on the Interstate highway I took part way to work. No damage was done but I was driving at a low speed on a city street on an icy day when it happened. After the repair, I drove the car to 183,500 miles and then sold it to a friend who drove it to 295,000 miles until he sold it to a third owner.

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Yes, thanks about the water pump advice. It's already failing as noted, so I'm going that far in.

I have a shop manual, so it's straightforward, but lengthy.

Another question, though. Does anyone know if, once the timing covers are off, is it possible to inspect for a damaged timing belt or impending failure?

Won't make any difference to what I have to do, but just curious for future maintenance and useful information for the group.

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Yes, thanks about the water pump advice. It's already failing as noted, so I'm going that far in.

I have a shop manual, so it's straightforward, but lengthy.

Another question, though. Does anyone know if, once the timing covers are off, is it possible to inspect for a damaged timing belt or impending failure?

Won't make any difference to what I have to do, but just curious for future maintenance and useful information for the group.

No, I don't think you can tell if failure is imminent since the belt itself almost never breaks but is instead taken out by the failure of the tensioner, idlers, water pump, etc. I suppose you could drive the car until the timing system fails which might be never. The reason I've never done this is that it is a safety issue. All power is lost when the timing systems fails ... not something you want happening when crossing a railroad track or making a left turn in heavy traffic.

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Good advice '90sl400! Just what I would have commented.

Guess I wasn't clear in my question. I wasn't concerned about driving it to the last and catching it just before it breaks, but just the opposite. If I'm going to breakdown I'd like it in my driveway.

I just bought this car - 206000 miles. Don't have any idea of the condition of the belt. No documented new belt since 89500, water pump is failing.

Once I was satisfied that the engine ran, didn't miss, knock or smoke, I shut it down, bought it, flatbedded it home courtesy of AAA and won't restart it until I have the new belts and waterpump installed since there doesn't seem to be consensus about interference in this engine.

I'm not sure if any other systems need work - power steering pump, alternator, ac compressor, etc I'd like a compression and oil pressure check. It would be nice to know what state they're in before I start so I can replace or repair them when I'm "in" that far.

It would be helpful to know whether I could chance starting the engine again and testing them before I start tearing it down, so having a look at the belt early on, could give me confidence about whether to start the engine and check things out before I begin the work.

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Power steering pumps on Lexus V8 cars improved somewhat by 1993 and are not as likely to fail. I went through countless power steering pumps in the 13 1/2 years with my 90 LS400. Mainly check to see it is leaking since a leaking power steering pump can cause the alternator to fail. It may seem tacky but some people fashion plastic protective shields for alternators on 90-94 Lexus V8 cars - there are photos of them on this forum. The "bottle of choice" for making these shields seems to be a Clorox container.

If the A/C works, don't worry about it except to ensure that the refrigerant level is correct.

These generation 1 V8 engines are strong and remain strong if they are properly maintained. The engine in my 90 LS was still running perfectly and using no oil between changes when I sold it at about 183,000 miles in 2003. The subsequent owner drove the car to about 295,000 miles before he it.

The 90-94 Lexus V8 engine is not interference but still could be damaged if the timing system fails at high engine speeds.

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Thanks again.

It occured to me that in all my review of the timnig belt and water pump replacement in the shop manuals I had never encountered any warning against turning the crankshaft if the camshaft timing was either off or out of synch - which would be expected if the engine there was an interfenence problem.

So, I finally got wise and read the manual more carefully.

There are two very relevant statements in the engine overview from the Lexus shop manual. Paraphrased:

- the valve springs are such that no "float" will occur under any circumstances.

- the pistons have depressions which prevent interference with the valves.

So it can be confidently stated that at least the early 1uz-fe engines are not interference engines and timing belt failure alone will not damage the valves or pistons. Nor will valve spring failure.

Anyway, I just finished running the engine and testing everything that could be tested before I started digging in to change the pump and belts. Everything is fine except there is no heat from the heater. I am sure this is because of an airlock in the system and the lack of coolant circulation.

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  • 2 years later...

Hi everyone. This is my first post. I'm in a pinch an so is my mechanic. I'm aware that my 92 SC400 is a non-interference engine. I just had the water pump and timing belt replaced. I'm told the mechanic manually turned the engine crank with a wrench and that he turned it two revolutions the night before, and that the next morning he decided to turn it again, but the engine was stuck(locked up). Does anyone know why this may have occurred? Any input would be greatly appreciated. Thanks

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  • 4 months later...

Old thread I know.  So, we all know it's a non interference engine.  A buddy of mine went to buy an engine and asked me a few things about it.  The place selling the engine called him and said sorry, it turns out the engine had a broken belt.  But they had another engine (both '95) and sold him that one, and also gave him the broken one for free.

He stripped down the one with the broken belt and found everything nice and clean inside, but had three bent valves.

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8 hours ago, Photon440 said:

Old thread I know.  So, we all know it's a non interference engine.  A buddy of mine went to buy an engine and asked me a few things about it.  The place selling the engine called him and said sorry, it turns out the engine had a broken belt.  But they had another engine (both '95) and sold him that one, and also gave him the broken one for free.

He stripped down the one with the broken belt and found everything nice and clean inside, but had three bent valves.

It is odd that the 95-97 Lexus V8 continues to be listed as non-interference in most charts including the current one from Gates when there have been a number of reports on Lexus forums of bent values when timing systems has failed.  The bottom line is that it is best to replace timing belts, tensioners and idlers and water pumps when driven by timing belts at the recommended intervals.  Not that timing chains can't present problems too but I'm glad that none of our current vehicles have timing belts.  My understanding is that Toyota no longer makes any vehicles that have timing belts - last one was in around 2009 IIRC. 

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  • 7 months later...

Yeah, I've found out they are interference engines. all this talk of of non-interference is airy fairy at best!

Firstly all timing belt lists say 4-0 litre V8 is interference and secondly Ive just had a seized water pump , which overheated the belt & snapped the teeth of the cogged belt!

 All over Red Rover, we now have bent valves. And the wife wasn't racing or pulling hard at the time either.

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