# 1991 3.0L V6 Problems



## Arayt (Jul 3, 2011)

I have a 1991 Pickup V6, I think the timing belt has broke. Can someone tell me if this is a the close valve /interference engine? If so what are my chances that it did not mess up a valve or piston?

I Was going about 50-60 and it just quit. I tried to crank it, the starter engaged and it sounded like the flywheel was spinning but nothing else.

I replaced the belt about 8 months ago (I've replaced it twice about 110k & 225k). I bought the truck new 20+ years ago & it has about 250k miles on. I hate to see it go. 

Any advice would be appreciated on were to start and what to check first.
Thanks Ray


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## smj999smj (Jan 1, 2006)

Nissan trucks with the VG30 engine used a 60,000 mile timing belt until 1994, when the switched over to the 105,000 mile belt. To answer your question: yes, it's an interferance engine and very possible that you bent some valves. Best thing to do would be to teardown the front of the engine, if you are sure the belt has broke (you can remove the distributor cap and watch the rotor while cranking the engine and see if it turns), and install the new belt, after correctly timing the cams and crank, of course. Install just the belt guide plate (the washer between the crank sprocket and crank pulley), the crank pulley and bolt (you can install the lower cover, if you wish, but not necessary for testing purposes). Tighten the crank bolt and see if the engine starts and runs (you don't need to run it long, so you don't need to reassemble the rest of the covers or coolant at this point). If it starts and runs well, you lucked out. If it doesn't start or starts and runs poorly, there's a very good chance of bent valves. If you want to confirm further, pull the plugs and do a compression test.


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## Arayt (Jul 3, 2011)

Many Thanks!! I was hoping for good news, but that life. I'll let you know what I find. Thanks Again.
Ray


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## Arayt (Jul 3, 2011)

*Should I stop, keep going or change gears*

Got her apart, the timing belt teeth were stripped. Tried to rotate the cam gears by hand and they would only turn so far. Now I'm wondering if I should continue on, being the truck has 250k+ miles on her. She is in above average shape (I bought her new 21 years ago) but with that many miles I'm thinking I should find an engine from maybe a wreck and swap it. What do you think? Appreciate any advice.
Ray


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## carldick (Oct 16, 2008)

Sounds like the belt wasn't properly tensioned last time it was replaced. This is a crucial adjustment. You can't rotate the cams or crank individually simply because it is an interference engine so this is not really telling you anything of value. It's not a hard job to pull the heads and at least determine the extent of the damage. In all the ones I've had come in here with broken belts, the only damage has been valves. Nicks in the piston tops but not to the extent where they needed to be replaced. Take the heads to a machine shop and have them rebuilt. The bottom ends of these engines are pretty tough. If it doesn't burn oil and has been maintained, I'd go with the head work before an engine swap. Always a question on an engine from a salvage yard. If you do the head work, be sure to replace all the exhaust manifold studs at the same time.


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## smj999smj (Jan 1, 2006)

"Sounds like the belt wasn't properly tensioned last time it was replaced. This is a crucial adjustment."

Keep in mind he's putting 110,000 miles on a belt designed to be replaced at 60,000 miles, I doubt that the installation was the problem. 

I would try to get the cams into their respective TDC #1 positions. If they jamb while turning, try slowly turning the crank by hand to see if you can move it into a position where you can get the cams to turn where you need them. That said, I don't ever recall having an issue turning the cams on a VG30E engine with the belt off (and I've worked on a lot of them), so, you may be right in that the damage is done. But, if you can get everything aligned, install a new belt, the guide plate, crank pulley and crank bolt, tighten. Turn the engine by hand and see if it binds or anything unusual is noticed. If it turns by hand, attempt starting the engine and see if it'll start and run as I suggested earlier. If indeed the valves are damaged, the choice is really yours to make. If the engine didn't burn oil before, you'll probably be okay with removing the heads and a valve job, or using remanufactured heads (try: $199 Rebuilt Cylinder Heads, Don't Pay for Core, High Quality, Baltimore MD. ). If you choose to swap the engine, you might consider getting a VG33E. It seems prices for these engines are no more and in many cases cheaper than the VG30E. Also, you get the advantage of more horsepower and the 105,000 mile type timing belt, plus it's a very easy swap, using the manifolds off your current engine (you may need to drill out the exhaust manifold bolt holes a little to accept the 10mm studs of the VG33).


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## carldick (Oct 16, 2008)

He said he replaced it 8 months ago at 225,000 and now has 250,000 on it. I stand by my statement. And, if you could turn the camshafts by themselves with the belt off it wouldn't be an interference engine.


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## Arayt (Jul 3, 2011)

*2 bent valves each head*

Well I got the heads off, at least 4 bent valves 2 on each head. The tops of the pistons dont look bad at all. What all should I have replaced in the heads and will the machine shops provide this? Any idea what the cost will be?
Thanks, Ray


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## carldick (Oct 16, 2008)

The machine shop should verify the valve guides with the bent valves are not cracked. Basically a good shop will verify the integrity of the heads before doing any machine work. Price is probably location dependent. My shop around here will rebuild both VG30 heads for $350 including a top end gasket set.
How did you set the tension on the belt?


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## Arayt (Jul 3, 2011)

An allen wrench and filler gauge. But my memory not as good as it once was.

I do have a Haynes Manual and should have followed their recommendations. Of coarse should have is the key word. 

I was going to blaming it on the belt, probably strait from China. It did come from NAPA though.


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## carldick (Oct 16, 2008)

My method is the half twist. At the middle point between the 2 cam sprockets, grip the belt with 2 fingers. Proper tension will allow you to twist the belt at this point 90 degrees.
When the the belt is on, loosen the tensioner bolt, turn the right bank cam sprocket a couple teeth counter-clockwise to let the spring-loaded tensioner take up the slack, and tighten the tensioner nut to spec. You should be able to turn the timing belt 90 degrees between the sprockets with your thumb and forefinger if it's properly tensioned. Over tightening can cause it to whine.
Also, if yours is original, it wouldn't hurt to replace the tensioner stud.


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## Arayt (Jul 3, 2011)

Seems more accurate than what the manual says. According to Haynes, tighten so you can fit a .35mm filler gauge between the belt and tensioner after several revolutions. Ill do the 90 degree twist next time.

Do you know if its standard for the machine shop replace all the valves, guides and springs or just the bad ones. 

Would you go back w/ new head bolts or reuse the old ones. The manual says reuse them but I've heard otherwise.

Ray


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## carldick (Oct 16, 2008)

Unlike the Toyota 3.0, the head bolts in the Nissan are reusable. Parts are over and above the rebuild price but you're very likely only looking at the 4 valves. It's possible, but unlikely the guides were damaged. Having the head deck ground should be part of the rebuild and will result in a good head gasket seal. And, I know it's a real pain in the butt, but I always re-torque the head bolts after 500 miles. Not everyone does.
Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com has an online parts catalogue you can use to get an idea of costs going with factory parts.


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## Arayt (Jul 3, 2011)

Thats good news. I'll reuse the head bolts. I Found a place today that can rebuild my heads for $185 each. Any recommendations on head gaskets, search found several different brands w/ a fairly cost difference. I definately don't want to do this again. I really appreciate all the advice. Other than the tensioner stud and exhaust manifold studs anything else you can recommend?
Thanks Again Ray


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## carldick (Oct 16, 2008)

There are a few things I always buy from the dealer. Head gaskets are one of them. There was no mention of any other work you did during the prior 2 belt replacements so now is the time, while you are in there, to replace the water pump, thermostat and cam & crank oil seals if they hadn't been done before. Oil seals are cheap and a pump or thermostat will require you to go through this whole front-end tear down again. 2 things I should have mentioned earlier. Try not to mix up the location of the valve lifters and closely inspect the rocker arms on the bent valves locations.


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## Arayt (Jul 3, 2011)

When I replaced the tmn belt last time I did replace water pump and t-stat. I'll have to replace the cam seals this time due to having the heads reworked. As you said now is the time to replace the crack seal also. What about the knock sensor? I've ketp everyhing seperated and marked for reinstall. The top of one lifter looks rough but the rocker arm is smooth. Do you know the torque setting for the head and rocker arm bolts? The manual I have only has a chart guide based on the type of bolt and the range is like 80-120 ft lbs.
Thanks Ray


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## carldick (Oct 16, 2008)

Never had a knock sensor fail yet.
Bring the crank and cams close to their in time position before putting the heads on and definitely before starting to torque them down.
11----7---3---1---6-----10
O-----O---O---O---O-----O

O--------O-------O----------O
------O-------O-------O
13---9---5---2---4---8-----12
Tighten in numerical sequence shown
1) Tighten all to 22 ft-lb
2) Tighten all to 43 ft-lb
3) Loosen all completely
4) Tighten all to 22 ft-lb
5) Tighten all to 40-47 ft-lb
Bolts 4,5,12,13 are longer than the others

Rocker arm final torque 13-16 ft-lb. Torque in stages like the heads


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## Arayt (Jul 3, 2011)

Good deal! I'm sending my heads off tomorrow hope to get them back in a few days. I'll be on pins and needles untili it runs again. Thanks for all the help!!! 
Ray

One last question- 
I have an option to get my head reworked or exchange them do you think it makes a difference? N_pa is having it done for me. Reputable folks and they have been using this head shops years.


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## carldick (Oct 16, 2008)

Probably no difference since they did the work on the exchange heads too I would imagine. Warranty?


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## Arayt (Jul 3, 2011)

Finally got my heads. 3 days turned into almost 3 weeks. After several excuses I was told my heads could not be rebuilt and had to be replaced. I beleive they lost my heads or gave them to somebody else. Anyway got a rebuilt set yesterday. Now my question, I've got them installed and I'm trying to set the timing. 

Can I bend a valve while rotating the the crank while setting #1 TDC? Also can this happen after belt install to verify timing is correct. I thought about installing the belt with with the rockers removed?? 
I've changed the belt before but then I rotated everything in to time before removal, of corse I cannot do that now. I Just don't want to screw this up.
Thanks Ray


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## carldick (Oct 16, 2008)

As I mentioned in a previous post, you should have brought the crank and cams close to in-time positions before bolting the heads on. If you didn't do this, and you rotate the crank without the timing belt on, you will definitely encounter valve lockups. If the timing was not close when you put the heads on and you had the rocker arms installed at this time, you may have already forced a valve into a piston top. Removing the rocker arms will prevent this from happening now while you bring the 3 pulleys into time.


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## Arayt (Jul 3, 2011)

Thanks I got it timed, and its going back together. Don't think I bent anything, but I had problems with the belt it only had two timing marks and they did not line up with the timing marks on the truck. Scratched my head for a while and then notice the third mark was the arrow. I counted the teeth and sure enough 40 from arrow to timing mark (cam to cam) and 43 from cam to crank.
Thanks Again!


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## carldick (Oct 16, 2008)

keep us updated on your progress


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## Arayt (Jul 3, 2011)

Well I got her back together and guess what? She will not crank. Not even trying to. I know I lined all three marks up, timed distributor w #1 cylinder. I even tore it back down last night and reset the timing again but with the same results. Of course if you do the same wrong thing again you’ll get the same results. Is there something else I'm missing? Talking about sick & disgusted. Any advice would be appreciated.
Ray


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## Arayt (Jul 3, 2011)

Update!! After another sleepless night with an unusually sore back and legs. Its hard to make them run w/o fuel. After timing it yet again, I said I wonder if she's getting gas. To make a long story short I had the fuel lines reversed. 
Now I got her started but it sounds like the timing belt is hitting the belt guard. I noticed after turning it a zillion times that it was not totally running true on the gears. What would make this happen? It sure makes you realize why it cost so much and man a person that does this full time has got to have patiences. Again any advice would be appreciated and thanks for all the help.
Ray


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## Arayt (Jul 3, 2011)

Update #2!! Tore it down one more time. Sure enough it was hitting the guard. I must have bent it during removal. Straighten it out put her back together started her up and she sound great. May need to adjust the idle it seems a little high. Boy I'm relieved. If I drank, I believe I’d tie one on. I say it all the time nothing I mean nothing beats experience and if you aint got it get advice. Great web site. Thanks again for all the help!!! 
Ray
I beleive after 20+ years of driving hoop-de its time for another truck!!


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## carldick (Oct 16, 2008)

One thing I always do before tearing into any vehicle is take pictures, pictures, pictures. Prevents hooking up fuel lines, vacuum lines, electrical, etc. incorrectly. Good job getting it done.


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## Blaine heilman (Sep 4, 2020)

Arayt said:


> I have a 1991 Pickup V6, I think the timing belt has broke. Can someone tell me if this is a the close valve /interference engine? If so what are my chances that it did not mess up a valve or piston?
> 
> Sadly yes, my friend and I have been working on his and we had to replace two exhaust valves. The key way may have gotten destroyed in the process also. Check the key way on the crankshaft behind the harmonic balancer. In his case the tenchner for the timing belt wasn't tightened enough and over time it got lose, he was going about the same speed up a hill and then the motor locked up


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