# 1991 D21 4-cyl rattling under valve cover



## TXhwyXE (Dec 20, 2006)

_1991 Nissan hardbody D21 2wd 4 cyl, 5 spd std. , apx 150k miles_

A couple of weeks ago I started to hear a rattling sound coming from under the valve cover. Back when it first started, I reved the motor a couple of times and it stopped but soon returned. This morning when I first started it, the rattling sound was quite loud so I shut the motor off and left it. This afternoon I just went out to start the motor and it was quite, no rattle. Any ideas what is happening?

About three weeks before the rattling started, I had changed oil and put synthetic motor oil in the engine for the first time. Could this have anything to do the rattling sound that started afterwards? 

Is is okay to put synthetic oil into this truck? I tried it to see how it would perform and if it would increase my gas milage. The motor does not burn any oil.

My engine tends to overheat in the summer in spite of radiator and coolant maintenance. I have not found out why yet. Thought I mention this in case it just might be related to the problem under the valve cover. 

Any discussion or ideas on this to help me fix my truck would be greatly appreciated. thanks.

Dan


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## cjserio (Mar 18, 2008)

My guess is that it's a lifter ticking or the infamous timing chain tensioner. If you're hearing it from the valve cover, it's probably a lifter.

I think it's fairly common and it tends to come and go...there may be a little dirt blocking one of the lifters.


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## Nissanman7166 (Feb 12, 2009)

I substitue a bottle of lucas oil in place of one of the quarts of oil when I change my oil. Its pretty expensive for a bottle ( 11 bucks ) but Lucas oil is one of the best products on the market. It also helps on vehicles whith high mileage and could help quiet down your lifter problem as it is pretty thick stuff.


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## Phatboy (Jan 30, 2009)

Right before an oil change put a bit of Tranny Fluid in it. Run it for a while. the tranny fluid is thinner than oil and can work through the spots where the oil cant. 

My 92 did this if I ever drove it over 70 for long periods of time. The previous owner put on some 'hammers' and low profile tires so I think it just kept the RPMs too high on the interstate. 

I am also a fan of LUCAS. they make some good shiot.


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## 5xHBowner (Dec 30, 2008)

My 91 does the same thing, but it has 242,000 on the clock. You could also try running some 89 octane in it to see if it helps.


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## CMax03 (Jan 17, 2009)

TXhwyXE said:


> _1991 Nissan hardbody D21 2wd 4 cyl, 5 spd std. , apx 150k miles_
> 
> A couple of weeks ago I started to hear a rattling sound coming from under the valve cover. Back when it first started, I reved the motor a couple of times and it stopped but soon returned. This morning when I first started it, the rattling sound was quite loud so I shut the motor off and left it. This afternoon I just went out to start the motor and it was quite, no rattle. Any ideas what is happening?
> 
> ...


Is it rattling or ticking? If it rattling then more than likely it should be coming from up front at the timing cover, If it's ticking then it's more likely the followers, tappets....pull your valve cover for either situation and check the timing for looseness and you can bump each lifter/rocker arm with a hammer hammer to make sure the valve aren't sticking or that the valve tappets aren't collapsed! GL!!!


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## SPEEDO (Jun 9, 2003)

cooling issue, have you checked the fan clutch..


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## smikster (Aug 12, 2008)

do a seafoam....helped mine...both of them


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## TXhwyXE (Dec 20, 2006)

Thank you everyone for replying. Your input is greatly appreciated.

I had someone recently tell me that the clattering was probably due to the synthetic oil. Due to its molecular structure, it flows more easily. What may be happening is that the synthetic oil is probably flowing out of my lash adjusters too fast for them to build up enough pressure to fully compensate for lash. This is usually due to fair wear and tear on your bearing clearances which reduce pressurized oil distribution throughout the engine especially at the upper extremities such as the valve train. 

At this time it does not appear to be happening as bad, maybe since the oil has some milage on it and not as effective as when new. Anyways, I decided from now on just to go back and use regular 10W30 oil on my next change since it had not caused the problem. 

As for the cooling problem, it was suggested to me that the problem was the radiator core having restrictions. Even though it may look very clean by looking into the neck, the core passages may be silted in and conventional flushes will not remove it. He said that one way to check it is to warm the motor up hot to operational temp then while the motor is running, check for cold spots by running my hand over the core on the font side. If blockage exists, I will feel hot and cold spots. 

You can cure this by either getting the radiator rodded out, sometimes a chemical flush will cure it or by renewing the radiator.

Since the radiator is 18 yrs old, I think that I will replace it with a new one. 

The cause I do not think would be the cooling fan clutch since it gets hot while going down the highway and has plenty of air hitting it.

Can I have any suggestions on what type of radiator to replace with? On the market I see a choice of one with plastic, then for about twice the cost is the all metal one. Should I avoid the one with plastic?


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## hans747 (Jul 14, 2005)

Replace your radiator with what's closest to yours and be careful of universal type radiators. I bought one for my wife's old volvo. It was designed for a few types of cars including hers. The problem is that it has connectors on it that don't apply to her car (they get capped off with rubber pieces). But the rubber pieces start cracking in about 6-8 months. I'm waiting for the day that I forget to change the caps and I overheat her aluminum engine.

As for your oil and ticking, here's my two cents: They say that when you add synthetic oil to an old engine for the first time, you're supposed to replace your filter after about the first 500 miles. That's because all the detergents in the synthetic oil loosen up the grime/cooked oil that's inside your engine, head, pan, etc. All that stuff flows around. It's worse if you have any builtup sludge in the pan.

Anyway, that's just something to think about.


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## hans747 (Jul 14, 2005)

Sounds like you're due for a new thermostat. If not that, maybe your coolant temp sensor is bad.


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## agraz21 (Mar 9, 2009)

What kind of synthetic did you use? Ive noticed a lot of cases of engine tapping if you run a cleaner in the oil ( apprx 10 to 15 min) before changing your oil, then using a high mileage sort of oil in your case id try the valvoline syn power maxlife synthetic and geared for lots of mileage that it could stop the knocking. I doooo nooooot recomend using trans fluid in your oil for any length of time, however it can be used as a cleaner, so add a quart drive maybe a day, then change it, as the others say lucas works wonders, and make sure you are using a weight of oil fairly thick, 10w30 at the thinnest if problems continue id try a 10-40


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## azbilly05 (May 21, 2009)

Hey folks I am having a similar problem with my 91 pickup. She has 387k miles on her and the ticking used to come and go right around the 3000 mark which was a sign to me to change the oil. Normally in times past right after the oil change the tick would go away completely till the next 3000 miles. This last time it did not I wonder if anyone here may think theres a possibility of a wrist pin and a lifter sounding alike. Any feedback would help guys. -Bill P.S. I try the lucas and let ya'll know the progress its been about 125k since I used it last.


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## TXhwyXE (Dec 20, 2006)

Hi, so you got a '91 also. I assume its a 4cyl D21. At that milage the bearing wear is probably to a point where the top end is not getting adequate flow and pressure. As I previous learn and posted above, the inadequate flow will not be enough to take the lash out of the lifters. 

The ability to maintain viscosity in the oil you are using may be wearing down around 3k miles. Thinner means not enough pressure buildup on the top end for a worn motor. Also going into summer months you are dealing with higher temps, faster oil weardown. My main ticking and rattle like sound comes from the front end of the motor moreso when the motor has been running for some time. I suspect loose and worn timing chain/tensioner adjustment wear. I just got back from a 700 mile highway trip doing 65 to 70+ mph. The motor ran smooth and performed terrific. My tires and shocks selection made the truck easy to handle and a smoother ride. 

At some point we may have to just pull the motor, and a simple rebuild to get our reliablity back to optimum performance. What I like about my D21 is that it is so easy to work on.


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## Outkast (Jan 29, 2006)

Pull the valve cover and check the timing chain guide over the top of the chain. I've seen dozens of KA's in the Altimas and Frontiers come in with that same noise complaint but only a few in the older hardbodies. This wont cost you any money just about 20 minutes of your time to check. And if it is the problem just pull it out. It's one of those things we could never figure out why the put it there.


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## rdixiemiller (Mar 6, 2008)

azbilly05 said:


> Hey folks I am having a similar problem with my 91 pickup. She has 387k miles on her and the ticking used to come and go right around the 3000 mark which was a sign to me to change the oil. Normally in times past right after the oil change the tick would go away completely till the next 3000 miles. This last time it did not I wonder if anyone here may think theres a possibility of a wrist pin and a lifter sounding alike. Any feedback would help guys. -Bill P.S. I try the lucas and let ya'll know the progress its been about 125k since I used it last.



Mine has been doing the same thing since 90K. It has 290 k now, no issues.I pay no attention to it anymore.


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