[esarratt]

I am doing a head job on my truck. Your thoughts and comments are greatly appreciated. Thank you for your help.

The truck was overheating and began to experience a severe loss of power which got worse and worse (over about 10 minutes). Eventually the heat gauge started to redline and I cut off the engine. I then had it towed to my mechanic. My mechanic said it had a blown head gasket. I wanted my mechanic to do the head job, but he is too busy so I am taking a crack at it. (Edit note: This paragraph was edited because I remembered details.)

This is the first time I have done internal engine work. I am experienced with replacing alternators, brakes, rewiring an engine and small engine repair.

I purchased the shop manual from Nissan and have been watching head gasket repair videos on Youtube. I have also been reading books and forums on head gasket repair.

My goal is to do a clean, high quality job and get another three decades out of the engine.

My plan is to:
1) Clean the engine
2) Document the locations of each bolt I remove with video and a marker/masking tape
3) Wedge the timing chain and examine it for wear
4) Take pictures of problematic parts for your feedback
5) Take the head to a machine shop for their opinion
6) Have the head magnafluxed
7) Have the machine shop remove and examine the valves
8) Use Nissan replacement parts

I will post more of my thinking plan as I learn more.

Here is a link to a simple Youtube video I did of the engine compartment:

Here are a few pictures I took before I start following the Nissan manual and taking things apart.

 

[rogoman]

Picture #2 shows frayed harness coverings; possible electrical problem. Several pictures show cracked hoses; probably should be replaced.
Before you go tearing into the engine, measure the cylinder compression yourself. What were the compression test readings? Standard: 173 psi; Minimum: 131 psi; Differential limit between cylinders: 14 psi

Your problem of loss of power maybe be due to something other then a blown head gasket. You may have a major intake system vacuum leak. To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.

 

[esarratt]

Picture #2 shows frayed harness coverings; possible electrical problem. Several pictures show cracked hoses; probably should be replaced.

I saw the frayed harness it was mentally on my list. I did not notice the hoses. Thank you.

Before you go tearing into the engine, measure the cylinder compression yourself. What were the compression test readings? Standard: 173 psi; Minimum: 131 psi; Differential limit between cylinders: 14 psi

Will do. The mechanic just said that it had a blown head gasket, I don't know if he actually checked the compression.

And, I forgot (its been a few months since this happened): The truck was overheating along with the severe loss of power; I cut off the engine when it started to red line on the temperature gauge.

A few questions about compression gauges:
1) I have several engines that I work on (all my own equipment): industrial diesel, marine diesel, small engines. I am looking at Mityvac and Innova gauges currently, but I am open to suggestions. Any particular type that you (forum members) recommend?

2) I have a gauge that has a needle that tells me the highest pressure the gauge went to. Are there any compression gauges that have a feature like this?

 

[rogoman]

If the mechanic said that the engine had a blown head gasket without doing a compression test, then it's just hearsay; maybe an easy way to make extra money at your expense. It would be a tragedy on your part if all that major head work was performed and you still ended up with your original problem. The overheating could be due to a plugged up radiator or a bad thermostat. A good rule-of-thumb: Always follow through with a thorough analysis/diagnosis.

The gauge you're showing is a cheap gauge. Most professional gauges have a compression release button. Here's a good gauge set that has rubber cone tips which is the easy way instead of those pesky screw-on adapters :

https://www.amazon.com/JIFETOR-Comp...940265610901&ref_=sbx_be_s_sparkle_mcd_asin_0

 

[[email protected] Gmail.com]

If the mechanic said that the engine had a blown head gasket without doing a compression test, then it's just hearsay; maybe an easy way to make extra money at your expense. It would be a tragedy on your part if all that major head work was performed and you still ended up with your original problem. The overheating could be due to a plugged up radiator or a bad thermostat. A good rule-of-thumb: Always follow through with a thorough analysis/diagnosis.

The gauge you're showing is a cheap gauge. Most professional gauges have a compression release button. Here's a good gauge set that has rubber cone tips which is the easy way instead of those pesky screw-on adapters :

https://www.amazon.com/JIFETOR-Comp...940265610901&ref_=sbx_be_s_sparkle_mcd_asin_0

Please make sure that you keep note of every bolt that you remove and where it. Came from I have the same truck andhaveFOUND that the bolts will kill you going back. Working head and tranny now. Took me 3 days 8 hour finally brought new. They may look the same in size but different In threads. Take this warning. Did the same head job. Will have to do it over after tranny . Gasket leaks. Wish you luck

 

[esarratt]

Please make sure that you keep note of every bolt that you remove and where it. Came from I have the same truck andhaveFOUND that the bolts will kill you going back. Working head and tranny now. Took me 3 days 8 hour finally brought new. They may look the same in size but different In threads. Take this warning. Did the same head job. Will have to do it over after tranny . Gasket leaks. Wish you luck

Thanks. I am labeling everything as I go along.

 

[esarratt]

Thank you for your help and input.

Result of my compression tests are:
Cylinder 1: 51 PSI
Cylinder 2: 18 PSI
Cylinder 3: 53 PSI
Cylinder 4: 57 PSI

I followed the directions from the compression gauge manufacturer (14mm hose, lubricate compression gauge threads, WOT, 5 seconds of cranking--I did 10). I did not however have the engine warm.

 

[esarratt]

I took pictures of the spark plugs from each of the cylinders where I tested compression.

Driver's side cylinder #1 spark plug

Driver's side cylinder #2 spark plug

Again, thank you for your help.

 

[esarratt]

Driver's side cylinder #3 spark plug

Driver's side cylinder #4 spark plug

 

[rogoman]

Thank you for your help and input.

Result of my compression tests are:
Cylinder 1: 51 PSI
Cylinder 2: 18 PSI
Cylinder 3: 53 PSI
Cylinder 4: 57 PSI

I followed the directions from the compression gauge manufacturer (14mm hose, lubricate compression gauge threads, WOT, 5 seconds of cranking--I did 10). I did not however have the engine warm.

All the spark plugs are heavily worn with several having heavy ash deposits. The cause of ash deposits are overheating caused by pre-ignition. For instance, due to ignition being too far advanced, defective ignition distributor, poor-quality fuel or a very lean mixture condition.

Are you sure you're doing the compression test correctly? The readings don't look right. Here's the compression specs:
Standard - 173 psi
Minimum - 131 psi
Differential limit between cylinder - 14 psi

Pour a table spoon of oil into each cylinder and re-test compression again. If all the readings are still very low, then the valves may be sticking or seating improperly; or all the rings are severely worn or are damaged. Sustained pre-ignition will damage the rings over time. If only two adjacent cylinders were very low, I would say a blown head gasket.

 

[saudade]

I remember doing my 86.5. It wasn't all that bad. I left the intake and exhaust manifolds on. If the head warped, it would have been easier to remove them on my bench. It wasn't warped.

There are quite a few diagrams to make the wedge. I had to make several until I had one that wedge in tight enough but I could easily pull out. Here's mine. (Click on the thumbnails for a larger picture)

Make sure you put your engine on #1 TDC Compression before you remove the pulley. Make sure the marks line up and use a sharpie to mark the spots.

Here's what my gasket looked like. Compression on #3 and #4 were similar to your readings.

Here the head and block.

There are 2 dowel pins that locate the head to the block. They may stick in the head, or the block or one in each. DO NOT LOSE THEM. Worse yet, DO NOT DROP ONE IN THE ENGINE (yes I'm shouting). I lost the one in the front driver side near the cam chain tunnel and thought it took a dive. Ended up pulling the oil pan to see if it fell all the way down. It didn't. Tried fishing it out with a magnet but there's too much steel there anyway. I was able to order a replacement from my local dealer. When I picked it up, I found the old on my bench where I first placed the head. It must have hitched a ride with the head, then fell out when I put the head down. I ended up wasting a week locating, and ordering it.

Good Luck!!

 

[smj999smj]

These engines tend to blow gaskets between the cylinders; if the head is badly warped, that could cause readings to be low across the board. Badly worn engine rings could also cause that, as well, so it would be a good idea to do a cylinder leakdown test prior to pulling the head. Wedging the chain is very important; wedge it not enough and the chain could slip, causing the tensioner to take up the slack. The tensioner can not be pushed back in with the front cover on and you will not be able to get the cam gear back on if this happens, so you would need to remove the front timing cover. If the wedge is too tight, you might find it very difficult to remove the wedge. As far as the cylinder head, if you are going to have it magnafluxed and the valves removed for inspection, you might as well get a valve job performed and expect the head to need a resurfacing. Another option, which would save some time, is getting a remanufactured head. This will come fully assembled with a cam, new seals and a three-angle valve job and be ready to install. As far as gaskets, you don't have to go with genuine Nissan; Fel-pro, Mahle and Victor-Reinz gaskets are all just as good. Get a "cylinder head gasket kit" and it'll have all or most of the gaskets you'll need. You'll also need some RTV silicone sealant and gasket maker. The head bolts are "torque to yield," so I would also purchase new head bolts. Get your thermostat and, if you need it, cap and rotor, from Nissan. I would recommend a Nissan water pump, if still available, only because it comes with the fan clutch and aftermarket fan clutches tend to be of lesser quality. Get spark plugs and, if you need them, ignition wires in NGK brand. It's not too bad of a job. Make sure you have a second person to help you left the head off and reinstall it. I usually reinstall it with the intake manifold installed and remove it with both manifolds installed. Check the exhaust manifold for cracks when you get it off.

 

[esarratt]

These engines tend to blow gaskets between the cylinders

I have heard.

Is there any value in using a higher performance metal head gasket or a gasket that has the cylinder holes reinforced with metal rings around the opening? I'd prefer to stave off future internal engine work as long as possible.

if the head is badly warped, that could cause readings to be low across the board. Badly worn engine rings could also cause that, as well, so it would be a good idea to do a cylinder leakdown test prior to pulling the head.

I suspect the rings in cylinder #2 are bad. I haven't had the time to post the videos and results yet, but my second compression test w/oil in the spark plug hole bumped up the compression to about 90 for that cylinder. I will post the exact numbers for all the cylinder retests I did w/in the next few days.

I bought a leakdown tester (and a Dewalt pancake compressor and 100' of Goodyear hose). The leakdown test is this weeks project.

Wedging the chain is very important; wedge it not enough and the chain could slip, causing the tensioner to take up the slack. The tensioner can not be pushed back in with the front cover on and you will not be able to get the cam gear back on if this happens, so you would need to remove the front timing cover. If the wedge is too tight, you might find it very difficult to remove the wedge.

I spent a couple hours reading about making/buying a wedge for the Z24 engine.

Question: If I have to do a top and a bottom engine job--because of the low compression (rings) in cylinder #2, is wedging the chain a moot point?

 

[rogoman]

I have heard.

Is there any value in using a higher performance metal head gasket or a gasket that has the cylinder holes reinforced with metal rings around the opening? I'd prefer to stave off future internal engine work as long as possible.



I suspect the rings in cylinder #2 are bad. I haven't had the time to post the videos and results yet, but my second compression test w/oil in the spark plug hole bumped up the compression to about 90 for that cylinder. I will post the exact numbers for all the cylinder retests I did w/in the next few days.

I bought a leakdown tester (and a Dewalt pancake compressor and 100' of Goodyear hose). The leakdown test is this weeks project.



I spent a couple hours reading about making/buying a wedge for the Z24 engine.

Question: If I have to do a top and a bottom engine job--because of the low compression (rings) in cylinder #2, is wedging the chain a moot point?

If you plan to remove the crankshaft to regrind the journals, when doing a full overhaul of the engine, then you'll have to remove the timing chain assembly anyhow in-order to remove the crankshaft.

 

[esarratt]

Just to make sure my results were accurate, I retested all the cylinders using a different compression gauge that had a rubber tapered tip (instead of a 14mm threaded tip). The new tip gave me a better seal and a little bit different (higher) results on some of the cylinders.

Result of my 2nd compression tests are:
Cylinder 1: 52 PSI
Cylinder 2: 27 PSI
Cylinder 3: 70 PSI
Cylinder 4: 65 PSI

I then tested the cylinders with a tablespoon of oil:
Cylinder 1: 103 PSI
Cylinder 2: 50 PSI
Cylinder 3: 123 PSI
Cylinder 4: 126 PSI

 

[rogoman]

Just to make sure my results were accurate, I retested all the cylinders using a different compression gauge that had a rubber tapered tip (instead of a 14mm threaded tip). The new tip gave me a better seal and a little bit different (higher) results on some of the cylinders.

Result of my 2nd compression tests are:
Cylinder 1: 52 PSI
Cylinder 2: 27 PSI
Cylinder 3: 70 PSI
Cylinder 4: 65 PSI

I then tested the cylinders with a tablespoon of oil:
Cylinder 1: 103 PSI
Cylinder 2: 50 PSI
Cylinder 3: 123 PSI
Cylinder 4: 126 PSI

Even though the readings came up with the added oil, the compression is way below the specs; in particular cyl #2:
Here's the compression specs:
Standard - 173 psi
Minimum - 131 psi
Differential limit between cylinder - 14 psi

You might consider performing a leak-down test on all cylinders. A leak-down or "cylinder leakage" test is similar to a compression test in that it tells you how well your engine's cylinders are sealing. But instead of measuring pressure, it measures pressure loss.

First you need to get a leak-down tester which consists of two hoses, one or two gauges, and a hand valve. To do a leak-down test, fully warm up the motor. Remove the spark plugs. On the cylinder that you're testing, bring the piston up to TDC on the compression stroke. Install one of the hoses into the spark plug hole; The other hose to a high pressure air supply. Apply a certain amount of air pressure by adjusting the hand valve. Watch the gauge which will indicate the percentage of leakage. An engine in great condition should generally show only 5 to 10% leakage. An engine that's still in pretty good condition may show up to 20% leakage. But more than 30% leakage indicates trouble.

The neat thing about a leakage test (as opposed to a compression test) is that it's faster and easier to figure out where the pressure is going. If you hear air coming out of the tailpipe, it indicates a leaky exhaust valve. Air coming out of the throttle body or carburetor would point to a leaky intake valve. Air coming out of the breather vent or PCV valve fitting would tell you the rings and/or cylinders are worn.

 

[smj999smj]

Back in the early to mid-80s, one of the things we did as a scheduled service (per Nissan) was to re-torque the head bolts. On the E-series engines in the Sentras, it wasn't uncommon to get a little bit of a turn on a head bolt when checking them. I'm sure a lot of those Nissan engines never had that serviced performed and as a result, it was not uncommon to have a head gasket fail on an early Datsun or Nissan engine. Of course, valve covers were a lot easier to remove in those days compared to today's engines and head gaskets have progressed, as well. There's no need for any special gaskets, as any head gasket made for that engine by a reputable company (I'm partial to Fel-pro) will work fine if the surfaces are straight and clean and the head is properly installed and torqued. New head bolts aren't necessary, but I would recommend them. If you are going to tear the engine down, then blocking the chain is not necessary, but you may want to do it, anyway, because when you remove the cam gear, having the chain blocked will give you some slack that the tensioner won't try and pull it, making it easier to remove the gear from under the timing chain. Also, keep in mind that when doing a cylinder leak down test, it will be hard to test the integrity of the rings on a particular cylinder IF there is a blowout in the head gasket between that cylinder and the adjacent gasket, as the pressurized air will move out of the cylinder you are testing and into the adjacent cylinder. You will tend to hear or be able to feel the air coming out of the adjacent cylinder's spark plug hole in those cases.

 

[esarratt]

Thank you for the gasket, timing chain and bolt re-torque information.

I actually bought and tried to perform a leak down test, but because my compression is below 100 (its a 100psi tester) the results were difficult to decipher.

I am in the process of removing the engine. I like the work. I am keeping every bolt and screw labeled in its own individual Ziplock baggie. I am also taking pictures and video of the process so I easily know how to put it back together again.

Those darned rusted muffler-pipe-to-exhaust manifold bolts! I soaked them with PB Blaster last night. If they don't come loose today I may just cut the muffler and be done with it. Unfortunately, because of the bolts' location, heating them evenly to break the grip of rust is impossible.

Those bolts will be a lot easier to get out with the engine removed and a muffler shop will make quick work of welding the pipe back together. It needs a new muffler anyway.

 

[smj999smj]

During a leakdown test, the piston needs to be at top dead center so that both valves are closed. Otherwise, it won't work because the air will blow into the cylinder and exit right out past one of the valves. Leakdown shouldn't be more than just few couple of PSI.

 

[rogoman]

I actually bought and tried to perform a leak down test, but because my compression is below 100 (its a 100psi tester) the results were difficult to decipher.

Just like SMJ said you don't need much pressure for a leak-down test. You can pump up the cylinder with less then 100psi. Watch the gauge which will indicate the percentage of leakage. An engine in great condition should generally show only 5 to 10% leakage. An engine that's still in pretty good condition may show up to 20% leakage. But more than 30% leakage indicates trouble.