Q45 broken timing belt _" Tech 45 "

[Jerry Parks]

I think my belt is broken. The car quite running on the interstate. Before that, I could hear chatter in the engine area. I'm getting plenty of fuel. What should I check before I get to the timing belt? AND, what are the steps to replacing the belt after the old one is broken? Does the Q45

have a rubber timing belt:? Thanks! - Jerry

[qship96]

no belt,just steel chains.if guides wernt done and it jumped time,your engine is toast.

[Jerry Parks]

The engine turns over, but does not fire. Does the engine lock up when the guides go bad?

[Q45tech]

Most times the timing slip bends the intake valves [all 8] on the driverside locking the engine up but it can just bend them in weird ways. Check compression on the cylinders. Assume your is a 90-92 or certain 93 Q.

[Jerry Parks]

Any idea what I should check next? Could it be a lack of fire to the plugs? How do I get to the plugs?

[duck3986]

Does the '98Q have chain guides?

[Jesda]

Chain guide failure -only- affects the 1990-1993 Q45. The timing chain is expected to last the life of the car, but replacement of the chain is "suggested" at about 250k.

I couldnt find the link to the Chain Guide explanation in Infiniti Articles (it said Forum Disabled), so here's pictures of broken guides and replacement on my 1992 Q45:http://www.q45.org/guidereplacement.html

If you heard a noise before your Q died, I suspect the guides failed and the chains jumped. Basically, its toast. Sometimes theyre recoverable, as some members have had chain guide failures that came close to causing severe damage but caught them in time. (Search for posts by azskygod). But others (PalmerWMD) ended up losing their motors.

-Jesda

[elwesso]

Does the '98Q have chain guides?

Yes... But the metal ones.... **All** cars that impliment timing chains use guides...

[texasoil]

By the way--the timing guide 'problem' is not unique to Infiniti. All MBZ 126 series V-8's had the same issue. They still recomend guide and chain replacement on new ones at 100K miles.

[DAEDALUS]

Yes... But the metal ones.... **All** cars that impliment timing chains use guides...

Guides are prevalent in DOHC motors, but not all cars with chains have guides, or even tensioners for that matter.

[Q45tech]

http://www.v8sho.com/SHO/ChainGuideFail ... ti...d=122

"A case in point is grinding noise coming from the timing chain cover area in 2000 to 2003 Ford Crown Victoria and Mercury Grand Marquis with the 4.6L V8. According to Ford Technical Service Bulletin 03-15-7, excessive wear in the timing chain tensioner arms can cause a noisy condition. The tension arm has an aluminum base with a nylon surface. So if you find nylon and/or aluminum particles in the engine oil, it probably means the tensioner, tensioner arms, timing chains and gear set all need to be replaced.

Ford also recommends changing the oil and filter to flush any nylon and aluminum particles from the crankcase. If the timing chain has worn through the tensioner arm into the tensioner piston, remove the oil pan from the engine and clean the debris from the oil pickup tube."The same goes for the Mazda-built 3.0L V6 in the Mercury Villager

Common problem on all makes IF you drive them long enough over their legal life of 100,000 miles.

Part of the cost of vehicle depreciation is the future cost of chain or belt replacements. Why 10 year old $50k cars are only worth 10% of new MSRP! They need $3,000-$8,000 worth of work.

[Chally]

Guides are prevalent in DOHC motors, but not all cars with chains have guides, or even tensioners for that matter.

All OHC engines with chains that I know, have guides. Most OHV with chains are as you stated.

[Q45denver]

You'll probably want to have an Nissan tech check it. You may only have to replace the driver's side head as Q45tech indicated. Let us know if you need a replacement head. I have both sides. I lost the bottom end on two engines so the heads should still be good.

[pito11213]

Hey Denver...what year motor are the heads from? Also what are you asking for them?

In response to the gentleman's question....Are you sure it is the timing. What are the symptoms of the vehicle. The car trying to turn over could simply be the fuel pump or the controller. There are so many possible reasons. Please be a little more specific about the vehicle, year, mileage and symptoms.

[Q45denver]

The heads I have are from a 1990 Q45. They were removed by the Denver Infiniti dealer after my car threw a rod 3 years ago with 120K miles on the clock and have been stored in my garage since then. I was thinking in the $100 range for the heads plus shipping but please make an offer. The other ones I have are from a Jap takeout engine installed 3 years ago by the dealer in my 1990 Q45. They are still on the car. The car runs but has severe bottom end engine noise.

[DAEDALUS]

Pito you got first dibs on 'em but if you don't want them I'm calling next, if the shipping issue can be worked out.

[Q45denver]

In case you are interested, the heads with attached intake runners are 65 lbs each. I could remove the runners to save on shipping but since they are aluminum they probably don't weigh much. My area code is 80224.

[pito11213]

Well D I wouldnt want to stand in the way of production so If you want them go ahead. I am still in the planning stage of just getting another motor for the Q and throwing some TLC into it while it is out. It is ashame too since the cars runs good. I have thought about doing the oil rings,bearings and valve seals but it is not the labor that scares me but the parts.

I thought changing the heads with some new rings might benefit me....What do you think?

[Q45denver]

Probably not worth the expense to just do the rings unless the engine has low compression. The rings are some kind of high tech design that rarely if ever fail. The same can be said for the valve train except if you still have the old guides. I'm not sure how much labor is involved in replacing the valve seals. Have you done a cylinder leakdown test? If you plan to rebuild the engine I'd replace everything and install forged rods. However, I think you might be able to still get a new short block which would be much cheaper. I just bought a used engine for mine for $700 plus shipping that the seller claims only has 50K miles and was running great prior to having an accident. The labor and warranty is usually a much greater expense than parts unless you do the work yourself or know someone. I've heard the figure of $10,000 thrown around to rebuild the engine.

[DAEDALUS]

The new bearings is what scares me. I assume that's main bearings. You have I think 7 sizes of bearings available, each is .0001" different from the next. Of the 3 machine shops I know around here, not one of them can measure a bore to .0001". One guy I told, he didn't believe me until I went back with the FSM to show him. He's been in the biz for 30 years.

[pito11213]

A short block is the motor without peripheral right?. IE alternator and such. Where did you get that for that price? I just thought that I didnt want to take a chance getting another engine that I know nothing about. This engine produces blue smoke but runs like a bat out of hell. As far as bearing Daedalus yes, it is the main bearings. My mechanic is the one who suggested it. I just wanted to do rings and valve seals. He has told me a labor rate of $800 is I want to just get another motor put in. ($400 each remove and replace) I think the best way to go would be a JDM motor hopefully for $1200 I wish for $1000. Then do all the maintanence with the motor out of the car. I guess time and funds will tell. But that is the general rule of thumb with a luxury performance car 15 years old.

[DAEDALUS]

The short block doesn't have the heads. It's just the lower end, with crank, con rods, pistons, bearings, etc. Long block has the heads, timing items, flywheel, water pump, but no other peripherals (alt, compressor, ps pump).

I searched Ebay for the bore gauges. Apparently they're not too hard to come by. Saw a nice one that had a resolution down to .00005", but it was $400. Even with that though, it just seems that human error in the measurement would be greater than .0001".

[Q45denver]

Ebay-I had the second highest bid so the when the first bidder backed out it was offerred to me. It is supposed to have all the peripherals which the Jap takeout I got last time didn't include. BTW I paid $1800 3 years ago for one but I did not shop around much for a better price and it included a one year warranty on the engine.

[nonigabriel]

Are ALL 1993 q45 are susceptible to broken chain guides also?

[Jesda]

Yes. There's a rumor that late-production 93 models may have used metal backed guides, but there is NO HARD EVIDENCE of this.

Assume your guides werent done. Have the front cover removed to find out for sure, or just have them done anyway since front cover removal is at least half the labor.Even if the dealer took care of it under warranty, they may have only done one side.

[nonigabriel]

Guides are prevalent in DOHC motors, but not all cars with chains have guides, or even tensioners for that matter.

I have an 77K miles 1993 q45 are they all susceptible to broken chain guides soon? This chain guide fail makes me worry.

[DAEDALUS]

Impossible to say. Most seem to fail after 100k, but some have failed before 50k. Roll of the dice.

[Q45denver]

Yes. There's a rumor that late-production 93 models may have used metal backed guides, but there is NO HARD EVIDENCE of this.

Assume your guides werent done. Have the front cover removed to find out for sure, or just have them done anyway since front cover removal is at least half the labor.Even if the dealer took care of it under warranty, they may have only done one side.

The 1993 engine I recently got for my 1990 had the metal backed guides according to the shop that is installing it. Since the car it came from only had 50K on the odometer, I think they are original to the engine. Best to take the front cover off and check to make sure.

[mixatonia]

In the past Ive seen many of the discussions on replacing the guides but I wonder if its something a diy shoujld really try.

I guess I should search to see if any garage diys did it with just the minminum set of tools. I havec about a thousand or two thsouand dollars worth bought over time as needed which isn't much - wrenches, screwdrivers, jacks, pliars, sockets, and such but which has worked for all the minor repairs ive made in the past such as radiators, alternators, water pumps, hoses, batteries, and such.

Is this like the oil pan where a diy should definatly sit out of the game?

[Jesda]

The issue isnt tools. Its precision. If the chain moves (which is why zip ties are used to secure them in place), you can royally bugger up the engine upon startup. The nice thing about taking it to a place like T3 is having the assurance that if a mistake is made, its on their dime (sorry Dennis) and not yours.

-Jesda