# Timing belt question **URL:** \ **Category:** Factual Questions\ **Created:** [May 31, 2015, 3:35pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259 "2015-05-31T15:35:24Z")\ **Posts on this page:** 14\ **Page:** 2
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [June 27, 2015, 5:28pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/21 "2015-06-27T17:28:12Z")
> [@Rick](#): > > In a word no. Timing belts are external to the engine block. Timing chains are internal to the engine block. Things that are internal get oil all over them constantly. Timing belts run dry (at least they are supposed to, as oil contamination can cause premature failure of the belt). Timing chains need lubrication so they are inside the engine. as always, someone has to be different šŸ˜‰ > **[Deep Dive: Ford 1.0L Ecoboost](https://www.thetruthaboutcars.com/2014/10/deep-dive-ford-1-0l-ecoboost/)** > > Brown paint isnā€™t available from the factory and adding diesel would require pumping out its fuel system, but Fordā€™s Fiesta SFE is practically built for the Internet. Though sales projection for the turbocharged, direct-injected three cylinder... ā€œ_As with some of Fordā€™s other recent small engine implementations, the belt is sealed and immersed in oil to reduce friction, reduce noise and increase the service interval. An inspection is called for at 150,000 miles, but Ford expects the belt to last the life of the engine. Thatā€™s great if they are right, but the replacement will be exceptionally complex if they are wrong._ā€ ---
**Author:** ![Throatwarbler\_Mangrove](https://avatars.discourse-cdn.com/v4/letter/t/8c91f0/32.png) [@Throatwarbler\_Mangrove](https://boards.straightdope.com/u/Throatwarbler_Mangrove)\ **Post date:** [June 28, 2015, 12:41am UTC](https://boards.straightdope.com/t/timing-belt-question/721259/22 "2015-06-28T00:41:17Z")
> [@Amateur\_Barbarian](#): > > Because of all the efficiency and power issues, Iā€™d always assume any modern engine is interfering until an authoritative reference (not some web list) says otherwise. > > We didnā€™t get these lightweight, high-power, high-mileage, high-durability engines for free, folks. We had to trade away the thumping, fix 'em-with-a-spoon, keep running half dead dinosaurs and all their ease of repair. Any engine with variable valve timing is an interference engine. So pretty much any OHC engine made in the last 10 years will be of the interference type. Engines using the same block have gone from non-interference to interference when the heads were updated to include variable valve timing. GM OHV truck engines might still be non-interference, but LS and new Hemi engines are. EDIT: Nah the newest GM trucks all have VVT so they probably are all interference now. ---
**Author:** ![Kenm](https://avatars.discourse-cdn.com/v4/letter/k/bc79bd/32.png) [@Kenm](https://boards.straightdope.com/u/Kenm)\ **Post date:** [June 28, 2015, 3:16am UTC](https://boards.straightdope.com/t/timing-belt-question/721259/23 "2015-06-28T03:16:25Z")
> [@Throatwarbler\_Mangrove](#): > > Any engine with variable valve timing is an interference engineā€¦ Not so. For one, the GM 3.5-litre pushrod variable-valve-timing overhead-valve engine with a timing chain is not an interference engine. ---
**Author:** ![TallTrees](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TallTrees](https://boards.straightdope.com/u/TallTrees)\ **Post date:** [June 28, 2015, 6:14pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/24 "2015-06-28T18:14:49Z")
Follow the manufacturerā€™s recommendation. This isnā€™t a suggestion akin to ā€œclean your windshield before starting a long road tripā€. If your timing belt breaks while the engine is running, you have a good chance of having a downward moving opening valve (or two) make contact with an upward moving piston head (or two). An undesirable possibility. Known to kill an engine by causing more damage than is economical to fix. ---
**Author:** ![Bunk17](https://avatars.discourse-cdn.com/v4/letter/b/e79b87/32.png) [@Bunk17](https://boards.straightdope.com/u/Bunk17)\ **Post date:** [July 2, 2015, 1:20pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/25 "2015-07-02T13:20:57Z")
3.3l is not an interferance motor. Son in law just had the water pump pully fall off while going down the freeway breaking the belt. It only had 20k since belt and pump change. New pump and belt and it runs great. That was on mothers day. Found a listing somewhere that had all toyota highlander v6s as noninterferance ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [July 2, 2015, 1:30pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/26 "2015-07-02T13:30:00Z")
> [@TallTrees](#): > > If your timing belt breaks while the engine is running, you have a good chance of having a downward moving opening valve (or two) make contact with an upward moving piston head (or two). An undesirable possibility. Known to kill an engine by causing more damage than is economical to fix. Itā€™s a good thing you mentioned that, Iā€™m not sure the OP has been told yet. > [@Joey\_P](#): > > if the timing belt breaks, the pistons will smash into the valves and cause a lot of expensive problems. > [@engineer\_comp\_geek](#): > > What this means is that if the timing belt breaks, then the valves may end up open when the piston comes up to the top of the cylinder. This usually results in the valve being obliterated, accompanied by severe damage to the piston and the inside of the cylinder. > [@JerrySTL](#): > > That means if the timing belt does break or slip, the piston will slam into the valves. That will ruin the engine and cost a lot of money to fix. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [July 2, 2015, 3:23pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/27 "2015-07-02T15:23:38Z")
> [@Joey\_P](#): > > Itā€™s a good thing you mentioned that, Iā€™m not sure the OP has been told yet. Oh yeah. Well aware of that. Iā€™ pretty sure itā€™s an interference engine, so a belt break would be bad news. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [July 2, 2015, 6:03pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/28 "2015-07-02T18:03:19Z")
> [@Bunk17](#): > > 3.3l is not an interferance motor. Son in law just had the water pump pully fall off while going down the freeway breaking the belt. It only had 20k since belt and pump change. New pump and belt and it runs great. That was on mothers day. Found a listing somewhere that had all toyota highlander v6s as noninterferance Sorry but the Toyota factory engineer I just asked about this disagrees with you. While Toyota doesnā€™t publish a list if interference vs. non Iā€™ll take his level of experience over yours. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [July 2, 2015, 6:50pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/29 "2015-07-02T18:50:02Z")
FWIW, the Gates timing belt guide ([huge PDF link](http://www.gates.com/~/media/Files/Gates/Automotive/Catalogs/Automotive/TimingBeltReplacementGuide.pdf)) says itā€™s not an interference engine. Toyota has never been very big on interference engines (unlike Honda) and at least if the Gates guide is to be believed the only interference engine with a belt theyā€™ve made this century is the 4.7L truck V8. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [July 2, 2015, 7:11pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/30 "2015-07-02T19:11:46Z")
Thanks Jack. Guess itā€™s not an interference engine. ~ enipla ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [July 2, 2015, 7:18pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/31 "2015-07-02T19:18:31Z")
on some engines (like my previous SRT-4) the valves wonā€™t be struck by the pistons, but thereā€™s a chance the intake and exhaust valves can strike each other (and bend) if the cams go out of sync in a certain manner. edit: oh, and also even on a non-interference engine, you can still have a valve-piston strike if the belt lets go at high engine speeds. ---
**Author:** ![Throatwarbler\_Mangrove](https://avatars.discourse-cdn.com/v4/letter/t/8c91f0/32.png) [@Throatwarbler\_Mangrove](https://boards.straightdope.com/u/Throatwarbler_Mangrove)\ **Post date:** [July 2, 2015, 11:02pm UTC](https://boards.straightdope.com/t/timing-belt-question/721259/32 "2015-07-02T23:02:26Z")
> [@GreasyJack](#): > > FWIW, the Gates timing belt guide ([huge PDF link](http://www.gates.com/~/media/Files/Gates/Automotive/Catalogs/Automotive/TimingBeltReplacementGuide.pdf)) says itā€™s not an interference engine. > > Toyota has never been very big on interference engines (unlike Honda) and at least if the Gates guide is to be believed the only interference engine with a belt theyā€™ve made this century is the 4.7L truck V8. Off the top of my head both the 2JZ-GE inline 6 with VVT and the UZ V8s that were used since the original LS400 are interference engines with belts. Itā€™s probable that these were only used in Lexus branded vehicles and not Toyota branded ones in the US market. ---
**Author:** ![cochrane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cochrane/32/10441_2.png) [@cochrane](https://boards.straightdope.com/u/cochrane)\ **Post date:** [July 3, 2015, 2:08am UTC](https://boards.straightdope.com/t/timing-belt-question/721259/33 "2015-07-03T02:08:11Z")
> [@enipla](#): > > Oh yeah. Well aware of that. Iā€™ pretty sure itā€™s an interference engine, so a belt break would be bad news. **enipla** , Iā€™m pretty sure **Joey P** was being sarcastic since it was mentioned at least three other times earlier in the thread before **TallTrees** made his post. Itā€™s apparent **TallTrees** hadnā€™t read through the entire thread before posting. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [July 4, 2015, 1:41am UTC](https://boards.straightdope.com/t/timing-belt-question/721259/34 "2015-07-04T01:41:02Z")
> [@GreasyJack](#): > > FWIW, the Gates timing belt guide ([huge PDF link](http://www.gates.com/~/media/Files/Gates/Automotive/Catalogs/Automotive/TimingBeltReplacementGuide.pdf)) says itā€™s not an interference engine. > > Toyota has never been very big on interference engines (unlike Honda) and at least if the Gates guide is to be believed the only interference engine with a belt theyā€™ve made this century is the 4.7L truck V8. The Toyota factory repair manual for this engine specifically warns of the possibility of a valve piston strike in the timing belt replacement instructions. That coupled with my conversation with a Toyota factory driveline engineer has me doubting the accuracy of the Gates guide. Sorry but I have to go with the factory on this one. [Previous page](https://boards.straightdope.com/t/timing-belt-question/721259.md?page=1)