Nissan 720 pickup w/ 230k miles on Z24 engine-- should I re-torque head bolts ?

[sage691]

Hi all !

 

Just joined the forum, 1st post.

 

I've had my 1985 720 pickup for about 7 years now. I bought it second hand and have only driven it about 30k miles since then. Never any major problems, just basic maintenance type stuff.

 

Anyway, last week I was driving to the post office and for the first time I noticed the temp guage was about half way. This was unusual because it had only been running 5 minutes and normally it would be 1/4 of the way up for that amount of time. Even on the hottest days of the year driving long distances that temp gauge would never make it quite halfway, just a bit under half was normal. So about 1 minute after I noticed that it started to climb ABOVE half way and so I pulled over immediately. I had blown a head gasket before on a 94 Nissan pickup because I was stupid enough to drive it 30 miles AFTER the guage went above half, and so I was NOT about to make that mistake again.

 

So I waited a bit for it to cool and then decided to check the radiator, and when I pulled off the cap there was pressure and the coolant came gushing out. FAWK !! Anyway, turns out there was a mechanic shop within 100 yards so I filled up a jug of water at a nearby convenience store and then filled the radiator and drove it over there. It drove fine once it was cooled down with no issues. I ckecked the oil dipstick and it looked perfect (no milkshake !), and the coolant looked nice and green in both the radiator and the overflow. At this point I'm thinking bad water pump, bad hoses, etc.

 

So they call me the next day and say it has a "blown head gasket", $2500 to repair and they do not suggest fixing it. OUCH !!! When I tried to talk to the mechanic I never really got a clear explanantion of how he came up with that assessment. So I had it towed back to my house and had my girlfriend's ex-boyfriend (a 40 year mechanic with a lot of experience rebuilding engines) come over and look at it. He did a top up pressure test on the radiator and there were no leaks anywhere. He looked at the exhaust and there is no white steam. What he did notice is that, with the radiator cap off from a cold start it would take approximately 4 minutes for the coolant to come flowing back out of the radiator. He said he suspected this was a bad thermostat, so we removed it and boiled it in a pot of water and lo and behold -- it was stuck shut !!

 

So I replaced the thermostat and the truck runs fine now. We did a "cold" compression test and 3 of the cylinders read 120 psi and one reads 95. So the next day I take the truck back to that shop and demand a refund of my money for a misdiagnosis (they charged me $85 just to tell me to junk my truck !!!). The mechanic was noticably frustrated. I showed him the bad thermostat and told him to go boil it in some hot water and see what happens. He said the ONLY WAY that water could come back out of the radiator like that was a blown head gasket ! My mechanic disagrees and says that is typical of a closed thermostat that is broken.

 

Anyway, sorry for the novel here but i am soon to get to my question ! So I got my refund, and then the shop mechanic calls me 1 hour later telling me to come over as he wants to do a "block test". So i go back and he pulls the radiator cap and sticks this thing that looks like a giant syringe with a rubber bottom into a radiator full to the top with coolant. Then he gets me to start the engine and says that if this blue liquid turns greenish or yellowish that my head gasket is bad. So he squeezes this bulb a few times and it turned dark aqua green. Then he tells me I have a "microscopic leak" in my head gasket. What I did not know at that time is that the kit he had is testing for combustion gasses and that the radiator needs to be drained a little so that the rubber bottom DOES NOT come in contact with coolant. But unless i am losing my mind, I swear that he stuck that rubber bottom directly in the coolant. I never added any more coolant since then and the level is still full to the top.

 

So now I don't know what to do as I am PARANOID about that "microscopic leak" he was talking about. As you folks can likely tell, I am not a mechanic !! I read on this site (and a few others) that these 720 trucks with Z24 engines are known for BLOWING HEAD GASKETS. "datzunmike" says that unless you re-torque the head bolts every tune up the head gasket will likely blow every 100k miles. My truck has 230k miles on it and I have never re-torqued these bolts in 7 years of owning it, and i have no way of knowing if any of the previous owners ever did this.

 

So my question is this: SHOULD I ATTEMPT TO GET MY MECHANIC FRIEND TO RE-TORQUE THE HEAD BOLTS IF IT HAS NEVER BEEN DONE WITH 230K MILES ON THE TRUCK ? I am worried sick about the possibility that this might somehow mess something up since I don't think it has been done before and the engine is so old. I can hear the old saying "if it aint broke, don't fix it" pounding in my head like a drum. The truck runs fine, no diffent than it ever did since I have owned it. But I am equally worried about not doing it and then kicking myself later!

 

 What do you folks think ? Can it possibly hurt to do this, or can it only help ? I know that the FSM says to do it one bolt at a time, and torque to 60 ft./lbs. in any order. Is it that simple, or am i missing some important details about the procedure ? If we do it I will replace the valve cover gasket too. I was also wondering if that lower psi in cylinder 3 might somehow be related to these bolts never being re-torqued before ?

 

I dunno, the other side of me says to rent that "block tester" kit from auto zone and do a proper combustion gas test first. If the liquid stays pure blue then maybe I'll just forget about this all together and get back to my life and stop riding my bicycle 15 miles a day(lol!!).

 

Then again, maybe re-torqueing those head bolts will fix that microscopic leak if it indeed exists ???

[datzenmike]

No engine can push water out the rad in 4 minutes. If the thermostat was stuck it would have to over heat to boiling to do this so 15/20 min of idling. However a blown head gasket will allow compression to leak into the water jacket and over pressurize the cooling system. This huge bubble of air will push the rad water out in seconds of minutes.

 

 

The gasket may already be well on it's way to blowing completely, no way to know, but likewise no harm in re tightening the head bolts either.

 

On a dead cold engine. Just loosen one bolt at a time and tighten it, then move on to the next.

 

 

BTW that $2,500 was his way of saying I don't want to do this job. At $100 an hour it's only 6 hours of work plus a $35 gasket. Never go there again. You can do this yourself if you borrow a few tools from your mechanic friend. Start with a torque wrench. You can do this.  .

[sage691]

No engine can push water out the rad in 4 minutes. If the thermostat was stuck it would have to over heat to boiling to do this so 15/20 min of idling. However a blown head gasket will allow compression to leak into the water jacket and over pressurize the cooling system. This huge bubble of air will push the rad water out in seconds of minutes.

 

 

 

 

Hi Mike,

 

 Well, I was actually just guessing when i said 4 minutes. My girlfriend was with him when he did this, not me. It may very well have been 15 minutes before the water came back up thru the radiator. I think she said it was idling for a while, and then the temp gauge suddenly started going up and that is when the coolant came flowing out.

 

 What I know for certain now is that the truck runs fine and the temp gauge stays below half with no overheating and no problems. When I changed the thermostat I let it idle for well over 20 minutes with the radiator cap off and the temp gauge stayed just below 1/2 and no coolant came flowing back out at any point -- and then i drove it for 20 minutes more after that !

 

 So how could the head gasket be blown then if the problem goes away by changing the thermostat ?

 I guess I need to do the block combustion gas test at this point to be sure. Maybe it could just be a leaky gasket getting ready to blow ?

 

 Does that one cylinder that reads 25 psi less than the other 3 sound like a head gaske leak to you ? That has me a bit concerned, but since it was a cold engine compression test maybe it is invalid.

 

 Thanks so much for your help ! I am still a bit afraid to drive it now until i know for sure what is up. I am not a mechanic, so changing out the gasket seems like a real daunting task for me. But I have the Chilton manual and have also read extensively about the process. This site has been really GREAT for my education on this !!

[datzenmike]

That's true about the thermostat.

 

 

A leak down test would point to a leaky gasket. Compressed air is pushed in through the spark plug hole. If you hear hissing at the tail pipe the exhaust valve is bad, at the intake the intake valve is bad, valve cover the rings are bad. If air bubbles out the rad cap the gasket is blown into the cooling system. If you listen to the spark plug holes on either side of the cylinder being tested and you hear hissing the gasket is blown between them.

[sage691]

 A leak down test would point to a leaky gasket. Compressed air is pushed in through the spark plug hole. If you hear hissing at the tail pipe the exhaust valve is bad, at the intake the intake valve is bad, valve cover the rings are bad. If air bubbles out the rad cap the gasket is blown into the cooling system. If you listen to the spark plug holes on either side of the cylinder being tested and you hear hissing the gasket is blown between them.

 

 

 

 

 

 

OK thanks, very helpful !

 

So this is different from the pressure test where he pumped air in thru the radiator ? I wonder if I can rent a leak down test kit from Auto ZONE. It sounds pretty definitive, maybe even better than the block test with the blue liquid.

 

So you remove the intake and exhaust side plugs for each cylinder and test one at a time ? I assume you have to leave all other spark plugs in ?

 

I know when he did the air pressure test from the radiator there were no leaks anywhere to be found, but I guess that test is not as definitive as this one.

 

The truck runs as good as it ever did right now, so I am remaining optimistic but want to be sure.

[datzenmike]

If it's running well now I'd just leave it, but I would re-torque the head bolts and keep an eye on it..

 

 

You'll have to look up how a leak down test is performed and you need a compressed air source. By compressing the cylinder, if there is a leak into the cooling system, bubbles will show up in the rad. I would suggest a garage do this but they can't be trusted to be truthful and will suggest the gasket be replaced just for the work. 

[Stoffregen Motorsports]

While reading this first post, my mind conjured a memory of the book "A Farewell To Arms". Triage is the name of the game here.

 

I think the damage has probably been done and anything you try to do at this point will only give you temporary relief. If it were my truck, I would do a leak-down test and then depending on the results, it may be as simple as adding some silver seal to the coolant.

 

Ok, guys. Don't jump all over me for recommending silver seal. If it's showing signs of leaking, this is the last line of defense.

 

What would a combat medic do?

[sage691]

While reading this first post, my mind conjured a memory of the book "A Farewell To Arms". Triage is the name of the game here.

 

I think the damage has probably been done and anything you try to do at this point will only give you temporary relief. If it were my truck, I would do a leak-down test and then depending on the results, it may be as simple as adding some silver seal to the coolant.

 

Ok, guys. Don't jump all over me for recommending silver seal. If it's showing signs of leaking, this is the last line of defense.

 

What would a combat medic do?

   Yeah, I was thinking about those sealent products.

 

   Do you know which one is the best for this ? I was thinking "Bar's Leaks", but maybe there is a better one ? Blue Devil ? I haven't tried this approach yet because I was concerned it might clog up the radiator or something else, and i was also a little skeptical. But if my problem is indeed a very small leak in the head gasket, then the Bar's product claims it will permanently seal it shut !!

 

 Today i think I am going to do that block chemical test and take a good look to see if the color changes any. From everything I have read it seems like this is the most reliable test I can perform myself right now. I really do not trust that mechanic who did this test that day, as i am almost 100% certain he stuck that rubber bottom of the syringe directly in the coolant.

 

Thanks so much for the advice, you guys are the greatest !!

[Stoffregen Motorsports]

I use the Alumaseal brand. I prefer this type of sealer over a liquid type because it works in a lightly different manner than the liquid type.

 

You can get it anywhere, but here's a link - http://shop.advanceautoparts.com/p/alumaseal-powdered-radiator-stop-leak-asbp-73/7120024-P

[720inOlyWa]

Oy veh!

The machine has given you good service for some time. You seem to like it. Just my personal opinion, but I think you already owe it a new head gasket, timing chain, and tensioners. These are, essentially, wear items and they are either worn out, or should be by this odometer reading. I‘d say jump in and fix it right. I did it with zero experience and it came out great. If I can do it, so can you. Seems to me, that’s what the Ratsun forum is for.

 

It cost me very little in the end to do this job myself and it wasn‘t all that hard. Now I only concern myself with re-torquing the head bolts once a year, a rather easy and fun little job.  Presuming you don’t have deeper issues (which often accompany blown head gaskets and overheating) go ahead, do it right, get it right. It isn’t that hard, or that expensive to make it pretty solid. I started with a shop service manual off of ebay. 20 bucks, I think.

 

My test is simple: would I drive it to Nevada today? If the answer is anything close to ‘no‘, I still have some work to do. I would not drive the truck you describe to Nevada today.

 

Having said this, I drove 15,000 miles on my head gasket job and this motor had overheated badly, perhaps twice, before I got it. The day I bought it, I drove it eight miles home on a bad gasket then rebuilt the top end. It has compression numbers only slightly closer than yours, but since my repair it has been very reliable for local use. Just great. These are hearty little motors and they respond well to theraputic repair. However, still it has a little knock when it is cold that says worn ‘wrist pin‘ or ‘rod bearing‘ to me. And the oil gets dirty fairly quickly, possibly suggesting worn rings. That is why it is up on blocks in my driveway today, getting a newly overhauled engine, new clutch, trans and carrier bearing. After that, Nevada is no problemo!

 

If I can do it...

 

I don’t believe in liquid remedies, myself.

 

Hey, the rain stopped. I better get back to it.

 

Good luck!

[sage691]

Oy veh!

The machine has given you good service for some time. You seem to like it. Just my personal opinion, but I think you already owe it a new head gasket, timing chain, and tensioners. These are, essentially, wear items and they are either worn out, or should be by this odometer reading. I‘d say jump in and fix it right. I did it with zero experience and it came out great. If I can do it, so can you. Seems to me, that’s what the Ratsun forum is for.

 

It cost me very little in the end to do this job myself and it wasn‘t all that hard. Now I only concern myself with re-torquing the head bolts once a year, a rather easy and fun little job.  Presuming you don’t have deeper issues (which often accompany blown head gaskets and overheating) go ahead, do it right, get it right. It isn’t that hard, or that expensive to make it pretty solid. I started with a shop service manual off of ebay. 20 bucks, I think.

 

My test is simple: would I drive it to Nevada today? If the answer is anything close to ‘no‘, I still have some work to do.

 

I don’t believe in liquid remedies, myself.

 

Good luck!

 Yeah, you are probably right. Man, I LOVE this little truck and would like to keep it going long term.

 

 Wow, looks like you have the exact same truck -- 1985 720 (2.4/2wd) with the Z24 ? I already have the Chilton manual, and I am pretty good at fixing things in general. Actually, I did change both the starter and alternator myself and those tasks were really no big deal.

 

 So how hard is it really to do this ? Like, how many hours did it take you ? I was thinking if I do it I would go ahead and get a genuine Nissan OEM head gasket off ebay for about $70. Plus, I know I will need that blue timing chain wedge (the longer one) as well. Then it seems once the job is done you need to drive it and then re-torque the bolts a couple more times until they settle in, right ?

 

This thing has never really overheated since I have owned it, so I feel pretty confident there is no warping and I will hopefully not need any milling of the head surface. My mechanic friend also has a straight edge to verify this. It seems there are a lot of DIY guys these days doing this and avoiding the rip off of shops, so this makes me more confident I can probably pull it off. And I am assuming if the head gasket has never been replaced in 230k miles, then it probably is pretty worn out by now.

[sage691]

I use the Alumaseal brand. I prefer this type of sealer over a liquid type because it works in a lightly different manner than the liquid type.

 

You can get it anywhere, but here's a link - http://shop.advanceautoparts.com/p/alumaseal-powdered-radiator-stop-leak-asbp-73/7120024-P

 Cool man, I just bought some of this stuff today !

 

 I have a quick question though: it says on the directions that it is designed to stop radiator leaks, but it says nothing about head gaskets. On the other hand, the Bar's product seems specifically designed for head gaskets.

 

 Are you saying that the Alumaseal can work for very minor leaks on head gaskets too ?

[sage691]

 

Having said this, I drove 15,000 miles on my head gasket job and this motor had overheated badly, perhaps twice, before I got it. The day I bought it, I drove it eight miles home on a bad gasket then rebuilt the top end. It has compression numbers only slightly closer than yours, but since my repair it has been very reliable for local use. Just great. These are hearty little motors and they respond well to theraputic repair.

  Yeah, I hear ya bro ! The thing is, I drive this truck about as little as anyone; I mean, we are talking 10 miles a day MAX with 10 hour breaks in between each 5 mile/10 minute drive. So it never gets a chance to overheat much anyway. Outside of that i will use it to haul things around for a few miles here or there.

 

 Just went to Auto Zone (20 minutes round trip) and let it idle for about 20 minutes AFTER I got home. The temp gauge looked like an Egyptian goddess to me, staying at about 40% of the way up -- and I am in New Orleans and the heat index is 105 degrees today !!!

 

 Running like this it is just hard for me to believe there are any major head gasket issues. But I will still do the block test today to be sure !

[Stoffregen Motorsports]

If it's a head gasket that's leaking compression into the coolant, you could find that nothing will do the trick. As with any leak, whether it's in house plumbing, tire or air line, the sealant will take the path of least resistance, ie- the leak. Ideally when the engine is shut off, the sealant will rush to the spot that is leaking and plug it up.

 

Yes, if anything is going to work, Alumaseal will, even on a head gasket.

 

I'm with Oly. Maybe it's time for an overhaul. Hell, even if you had a shop completely go through the motor, you could be all in at a couple grand.

[sage691]

Well gentlemen, it appears that I was the victim of an unscrupulous mechanic who lied not only once, but twice !!!

 

I just finished a very thorough block test, and the results are a firm negative for combustion gases in the coolant.

 

I did everything by the book:drained the radiator at least 4 inches down from the top, filled up the test tube to the fill line, and started her up. As per directions, with engine warm and idling, I stuck the test tube into the radiator opening and squeezed the aspirator (black bulb) for 2 minutes and the liquid abslutely did NOT change color. Heck, I even let it run for another 10 minutes just to be sure, kept squeezing the bulb intermittently, and that sky blue liquid showed no signs of changing !

 

 I have attached a photo (in my profile signature) of the used liquid in a glass, right next to the bottle of unused test liquid. Looks pretty darn blue to me !!!

 

 So I think I will get some good sleep tonight (finally !!) and contemplate whether I really want to do anything more right now -- other than re-torquing those head bolts and putting on a new valve cover gasket. Like I said, the truck runs like a champ after changing that $10 thermostat, and I really drive it so little that I doubt anything major is on the near horizon.

 

 What really pisses me off is that a misdiagnosis over a frickin simple $10 part has caused me weeks of frustration and fear. I am an honest person, and to think that a certified shop technician would blatantly lie to me like that is very troubling. I mean, when they first told me "BLOWN HEAD GASKET, $2500 TO FIX" and "WE DON'T RECOMMEND IT !!" there was a brief moment where I conisdered just leaving it there on the street and junking it.

 

 I sure am glad that I was smart enough not to do that !!

 

 Some mechanics (even at supposed reputable shops) can be dishonest people -- lesson learned !

[datzenmike]

Mechanic lives matter too.

 

 

 

 

This simple test show that you can do just about what any mechanic can do. If you are going to own a vintage auto you will have to do most of the upkeep too.

[KoHeartsGPA]

Check your spark plugs after running for couple hours, if one or more look like this....coolant is coming into the combustion chamber...

[sage691]

Hi guys !

 

Me and my mechanic buddy are going to re-torque the head bolts tomorrow on my 720/z24. So I wanted to post the steps here just to check with you experienced dudes if I have everything right ! He told me he has a "ft./lbs." torque wrench and a 10mm alan key/head (as precribed here).

 

Step 1: cold engine

 

Step 2: remove radiator cap to make sure no pressure remains

 

Step 3: remove air filter assembly

 

Step 4: remove screws/bolts to valve gasket cover and open door

 

Step 5: loosen one head bolt at a time (any order) to a quarter stroke, then re-torque to 60 ft./lbs. Do this for all 10 bolts and YOU ARE DONE !

 

Step 6: replace valve cover gasket with new one and shut door, place screw/bolts back in and tighten

 

Step 7: replace air filter assembly

 

 

 DID I LEAVE ANYTHING OUT ? IS IT REALLY THIS SIMPLE ?

 

I am praying that the previous owner did not do anything stupid, like replacing the original bolts with TTY stretch bolts !!!!!!!!!!

[datzenmike]

For re-torquing the head only #1, #4, #5 and #6 are needed. Loosen the bolt fully, a full turn should be enough.

[sage691]

For re-torquing the head only #1, #4, #5 and #6 are needed. Loosen the bolt fully, a full turn should be enough.

Thanks Mike !!!

[datzenmike]

Once done and warmed up.... Might be a good idea to check/set the valve lash?

[Stoffregen Motorsports]

Not a bad idea to relieve the radiator pressure before retorque.

[datzenmike]

The engine should be cold for doing this and the cooling system is either in a neutral or slightly negative pressure state