The case of the raising dipstick


#1

I have a 1997 Nissan pickup 2.4 4 cylinder that I’ve had several years . Mainly only gets used at my rural property . Doesn’t smoke or use oil & seems to run well . Right now my son is using it daily . It has come to my attention that every time the hood is raised after the vehicle is used the oil dipstick is about 1/2 - 3/4 inch up from its seated position . No oil is coming out of the tube . I can’t remember the last time the pcv valve was changed . Anyone think the pcv valve might be the problem ?


#2

That was going to be the first item I suggested. You can also check to see that it fits snugly when in the home position… Sometimes the rubber stopper type stops shrink up making it loose. I even saw one time when the hood insulation was acting like a crane if you will whenever you lifted the hood… so look at the hood underneath to be sure its not pulling it out.

More likely is too much crank case pressure… Just follow that course of thought. Loosen the oil filler cap a little bit…and run the engine…see if the stick pops out…if not…youre on the right track. Pretty ez to figure out.

Blackbird


#3

Could be air pressure pushing the stick up. A compression test might be helpful to determine engine condition.


#4

If it’s not a PCV problem it’s likely going to be something far worse; as in a compression issue mentioned by Barkydog.

Many years ago a friend of mine owned a '66 Ford pickup with the 300 6 cylinder. At close to 300k miles the blowby was so bad that after startup if the throttle was blipped a bang could be heard on the hood. The bang was the dipstick being blown out of the tube.
Choosing to keep driving it until the end he just rigged up a piece of coathanger to hold it down.


#5

The old truck only has about 130,000 on it . It hasn’t been a whole lot of miles since it had new plugs , wires , distributor cap & rotor . I change the oil & filter & air filter on a regular basis . I remember changing the fuel filter but the more I think about it I can’t ever remember replacing the pcv valve . I’ll stick a new one in & see if that fixes it . If not I’ll dig deeper .
I did some googling & it seemed like every thread I could find that someones dipstick was raising from the seated position , their vehicle was also blowing oil out of the dipstick tube . As I said there is no oil coming out . I hope it doesn’t turn out to be a compression problem .


#6

Make sure the PCV valve is getting vacuum (port and hose aren’t clogged) and the breather port to the air cleaner box isn’t clogged.


#7

The crankcase has a large diameter vent hose from the valve cover to the air filter housing. Check that hose to be sure it is open.


#8

@circuitsmith
I’ll definitely check those things when I get my son & the truck corralled long enough.
@"Rod Knox"
I remember disconnecting that hose when removing the air cleaner & I did reconnect it .
I’ll check to see if it’s open .
The truck isn’t displaying any symptoms of serious problems so I’m really leaning toward a pcv related issue .
My son stopped by this morning on his way to the tire shop to get 4 new winter tires for it . I may never get it back . lol . Regardless , we’ll need to fix the problem I’ve described .


#9

Blow By is real people… certaily could be that… Too much blow by and the PCV is overwhelmed. This one will not be hard to figure out. A compression test, and or a Leakdown will provide pretty fast results after the really obvious items are ruled out.

Blackbird


#10

It’s turned into winter here & colder than a well diggers butt so as long as it keeps running reasonably well I’m not going to worry too much about it immediately . Suggestion & advice are always welcome as sooner or later I’ll need to tackle it .


#11

Normal Combustion Moisture In A PCV System Can Freeze The PCV Valve In Freezing Temperatures. Some Manufacturers Have Had Problems With This Throughout The History Of PCV Systems.
CSA


#12

Good thinking @CSA. Short trips in damp air could cause significant moisture to accumulate in the crankcase vents where it would freeze over night. Only after a very extended highway drive would the under hood temperature melt and evaporate the ice. In fact the ice at the air filter might not ever melt until the ambient temperature rose above freezing.


#13

This issue shouldnt be hard to figure out. Youre already on the right track…you may find that the cause is not worth troubling over. If its blow by…the only recourse is to rebuild the engine. If this were my vehicle…I would drill a tiny vent hole in the stick stopper…to release excess pressure and prevent the stick from popping up. This isnt a serious issue per say…its cause can be serious…but not one that will stop it from running exactly the way it is for years to come. Im sure you will figure it out. If its blow by and the truck runs fine otherwise…its just part of how the engine wears out slowly over time. You can more than likely ignore it as the true repair will exceed what you want to get into. Hopefully its the PCV…simple enough.

Blackbird


#14

This is an old thread but I like it when people report back so that’s what I’m doing . I finally got around to replacing the pcv valve & no more raising dipstick . I had my doubts when I removed the old one because it was fairly clean & rattled when shook .


#15

Sincere thanks for posting back. We try to help people because we care, and it feels good to know a good result. It’s even good to know bad ones, 'cause we can learn from them.

Sincere best,
TSM :smiley:


#16

This is an interesting thread. It didn’t occur to me until now that a dipstick that won’t stay down where you put it is a clear indication of pressure in the crankcase. Although it seems obvious if you think about it. And those pcv gadgets, every one I’ve ever tested rattled like a rattlesnake when I shaked it, but that never seemed like a very good way to test one. It has to do a fairly complex function of metering the volume of crankcase airflow based on the engine use, so how could just shaking it provide much in the way of diagnostic information? I mean other than if it didn’t shake at all you’d know it was clogged up I guess.


#17

Shaking it is actually a great way to test it. A PCV valve is only a loose chunk of metal (check valve) that allows free flow in one direction while restricting flow in the other direction. It’s just a housing with a rattley-loose loose “piston” inside. Its real function is only to prevent backfires (not uncommon in the days of carburetors) from passing into the volatile gasses under the valvecover and igniting them, causing a fire. It’s not a metering device, just a check valve. A lot of modern cars don’t have PCV valves. With fuel metered by a solenoid operated valve and sprayed in pulses at the intake port rather than flowing freely at the throttle plate based on vacuum at the venturi, there’s really no reason for a PCV valve anymore.


#18

This diagram is where I got the idea that the pcv valve is more than just a check valve.


#19

Never saw one like that. I guess I’ll have to do some additional research.


#20

I once bought a Plymouth Duster with a slant six for $150 as a work car. It only had to transport me, my radio box and a bag with small tools and some clothes in it to work a few times a week.

When I bought it it would blow the dipstick right out and it smoked.

Why did I buy it, I thought I told you it was $150.

The guy I bought it from only lived 1/2 mile from work and the oil was thick and tar black.

I changed the oil to Valvoline 10w-30 and changed it again twice at two week intervals. I also flogged the engine as hard as I could, It was a stick and I revved it out in first gear a lot.

Every once in a while it would hiccup and actually jump a little bit as the rings freed up with a puff of smoke.

After about 6 weeks, the blowby was gone and it burned no oil between 3000 mile changes.

Good engines those slant 6s.