sonnyg22

I'm attempting to find out conclusively if this particular engine is an interference or non-interference engine. I've contacted several quality mechanics in the Fresno,Ca. area and all have indicated to me that it is in fact a non-interference engine, but when I brought this to the attention of the mechanic who recommends replacing the engine with a low mile Japanese engine due to damage to the existing engine from the timing belt breaking, he showed me a manual regarding "timing belts" and under the SC400 engine it stated that it was in fact an interference engine and would incur severe damage should the timing belt break. I'm just trying to get a clear cut answer regarding this engine. Any info would be greatly appreciated!

alexulan

this was found over the web. Not sure how accurate it is.

The orginal 1UZFE is non-interference at 10-1 compression but the 1995 going to 10.4-1 is interference and the 10.5-1 VVTi in the GS400, SC400 and LS400 from 1998 on are all interference engines

sonyman

From what I have heard, alexulan is correct. Pre-VVTI (early) engines are non-interference, while the newer VVTI motors are interference. Your motor should be fine.

Scott

PERRYinLA

A timing belt break is a rare occurance. Any details on it? At what mileage did it happen, and was it the original belt from the factory? Did it break because the water pump seized up (the usual case)? Did it happen on startup, or on the road?

sonnyg22

The timing belt broke during driving. I bought the car from the 2nd owner who said the belt was replaced a second time at 160k, but now in retrospect might not have been. I currently have the car at a repair shop and the mechanic indicated to me that I'm going to need to rebuild the top half or replace the engine. It's funny that you stated the belt breaks in most cases to a faulty water pump because when I was in the shop a mechanic pointed out that the belt was melted or got very hot in some spots which may have caused it to break. Back to your question, the car itself had 192k original miles on it and I'm not sure if it was a factory belt or not. I've been told that if it is not an interference engine I should be in the clear. How does one properly diagnose this situation without taking the head off or pulling the whole engine and replacing the timing belt and water pump? Any info would be greatly appreciated!

PERRYinLA

The '92 engine is definitely non-interference so if the car was running fine before the break, I don't see why the mechanic wants to pull the head- you might want to challenge him on that.

The more you know, the less likely you'll have to pay for uneeded repairs, so I suggest you take some time to use the "search" feature and read up on this subject- there are dozens of informative threads on the maintenance and SC300/400 forums. One thread describes how to remove the black plastic covers over the cam sprockets so you can inspect the belt (or what's left of it).

sonnyg22

Thanks for the info. I have had the opprotunity to view the timing belt at the shop and it is in bad shape. Yes, the engine was running fine before the belt broke. With this being said in your opinion should I be fine with the repairing of the timing belt and waterpump only? What is the best way in your opinion to diagnose this problem w/o taking off the head. The mechanic is stating that if he replaces the timing belt at a cost of 5-6hundred dollars and the car doesn't run due to a faulty engine, then consequently I will have lost that money. His suggestion is that I pay 1,095 for a 30,000 mile engine and pay him 700 for labor and have a relatively new engine. What's your opinion? Thanks for all of your info.

sonyman

I think your mechanic is pretty shady. If your timing belt is the only problem, then you shouldn't need a new motor, or any head work because it is non-interference. My advice is to just replace the TB and related parts (water pump, pulleys possibly), and/or get a second opinion from a different mechanic.

Scott

PERRYinLA

This is an internet diagnosis, so I can only go on what you've typed here. I've not read anything that indicates your engine is faulty, except for a broken belt. $500-$600 for a new belt (and water pump and assorted other parts) is quite a bargain- make sure no corners are cut.

As I said above, if you'd search a little, you'd learn, as I did when I first joined up, that our V8's can last a long time with regular care, and it is rare a new engine is needed (that's why used engines don't cost that much- there is not much demand for them).

You keep asking how to diagnose this problem. Since you've already seen the broken belt, what's to diagnose?

sonnyg22

Thanks again for the info. When I say diagnose I'm pertaining it to any valve or engine problems? How would one diagnose the possibility of that occuring?

sonnyg22

Or is it impossible for any engine damage to occur with a non-interference engine when the timing belt breaks?

mtsao

Here are two basic animations of how your engine works:

http://auto.howstuffworks.com/engine1.htm
http://www.samarins.com/glossary/timing_belt.html

On a non-interference engine, there is enough clearance between the piston and the valves that even if the timing belt breaks and the valves are in the open/down position in the cyclinder, the piston won't make contact with them. Not so in an interference engine.

Since you have already contacted some other mechanics and they've also confirmed that it is a non-interference engine, but your mechanic disagrees, I would be a little wary of him...it does seem a little shady...

Good luck!

sonnyg22

thanks for the info. greatly appreciated!

sha4000

iTrader: (1)

your mechanics advice is def. suspect i would take the car somewhere else since he keeps insisting that you do work that you most likely do not need. i see NO reason for a new engine based just on a broken tb for a non-inter. engine. what exactly is he basing his diagnosis on? the timing belt? if so i wouldnt trust him and if he fixes the tb and the water pump i suspect that you might be back in his shop in no time. its your call though, everyone here has given good advice that i think you should take

Vegassc400

Take the car somewhere else. A second opinion will never hurt.