SatoRich Posted March 27, 2020 Report Share Posted March 27, 2020 I have a 1984 720 with the Z24 2.4L engine. Have had it about 9 months and have done tons to bring it back to it's original glory, I bought it with 113k so it was in pretty good shape. I've taken two dirt bikes out to ride in the bed and have had no issues. Couple weeks ago I maxed the load with 1000 lbs and tried to drive on the hwy 60 miles back to my destination and didn't make it. About 45miles was the farthest I got. Engine started making a metal on metal ticking/tapping noise and was losing power. When I tried to accelerate, I had very little power and the noise got significantly louder. I stopped as soon as I could and had it towed the rest of the way. After looking into it further I'm stumped. I'll start it, and the motor literally shakes side to side, way out of the norm. It doesn't make the noise until it's under load. I've checked all the vacuum lines, EGR valve, has new plugs, wires, cap, rotor and the timing is fine. I'd rather explore more info/opinions before I open the motor with hopes it's something easier. Love the truck! Help! 1 Quote Link to comment
datzenmike Posted March 27, 2020 Report Share Posted March 27, 2020 I don't expect a rod bearing from your description as you probably had it full of oil and a rod is a loud tap that transitions to a dull sledge hammer knock sound. In addition there is no power loss. The Z24 is notorious for blowing it's head gasket however, and the sound can often increase with load. Usually it fails between cylinders, often into the cooling system. I guess a compression test is easy and cheap to confirm this. Expect one or two adjacent cylinders to be significantly lower than the other two and the compression will seesaw back and forth between them never reaching maximum. Naturally where would be a loss of power. Blowing into the cooling system usually presents with steam out the exhaust and or compression forcing coolant out the rad overflow into the coolant recovery container. If driven far enough, steam condensation will be forced past the rings and mix with the oil making it chocolate milk color. Just to be safe, take the valve cover off and look at the cam and valves. Turn the engine over with the starter and watch each valve move, on the off chance a rocker arm has broken. I'm not expecting this as the noise would not depend on load. Replacing the head gasket is just wrench turning, it's not magic BUT there is ONE big thing to avoid. Do NOT take the cam sprocket off without securing the timing chain tensioner so it can't fall out. If you are doing the work find out how. If your mechanic is, discuss it with him he may not be aware of it. If not, add a few more hours labor and some parts to fix this. On the Z series engine there are no lifters or push rods. The rocker arms ride directly on the overhead cam. 1 Quote Link to comment
SatoRich Posted May 29, 2020 Author Report Share Posted May 29, 2020 On 3/27/2020 at 8:50 AM, datzenmike said: I don't expect a rod bearing from your description as you probably had it full of oil and a rod is a loud tap that transitions to a dull sledge hammer knock sound. In addition there is no power loss. The Z24 is notorious for blowing it's head gasket however, and the sound can often increase with load. Usually it fails between cylinders, often into the cooling system. I guess a compression test is easy and cheap to confirm this. Expect one or two adjacent cylinders to be significantly lower than the other two and the compression will seesaw back and forth between them never reaching maximum. Naturally where would be a loss of power. Blowing into the cooling system usually presents with steam out the exhaust and or compression forcing coolant out the rad overflow into the coolant recovery container. If driven far enough, steam condensation will be forced past the rings and mix with the oil making it chocolate milk color. Just to be safe, take the valve cover off and look at the cam and valves. Turn the engine over with the starter and watch each valve move, on the off chance a rocker arm has broken. I'm not expecting this as the noise would not depend on load. Replacing the head gasket is just wrench turning, it's not magic BUT there is ONE big thing to avoid. Do NOT take the cam sprocket off without securing the timing chain tensioner so it can't fall out. If you are doing the work find out how. If your mechanic is, discuss it with him he may not be aware of it. If not, add a few more hours labor and some parts to fix this. On the Z series engine there are no lifters or push rods. The rocker arms ride directly on the overhead cam. Yep you called it! Blown head gasket as to which part of the gasket had gotten lodged in the cylinder which created the tapping noise I heard. My mechanic found that using a bore scope. Thanks for the advice! Is there a certain milage that they are prove to going out? 100k-ish I would presume. Quote Link to comment
datzenmike Posted May 29, 2020 Report Share Posted May 29, 2020 Roughly every 100K. Once fixed re-torque the head bolts every tune up, or once a year. The procedure is this... On a COLD engine, loosen ONE bolt and immediately tighten to 60 ft lbs. Only now can you move to the nest bolt. NEVER have more than ONE bolt loose at the same time. You can do them in any order you like front to back, back to front left to right what ever you like. 1 Quote Link to comment
yenpit Posted June 9, 2020 Report Share Posted June 9, 2020 Hey satorich, I'm in Arvada, where are you in Colorado? I don't have any Z24 parts, but have lots of L series, a 620 parts truck & a 720 parts truck! Let me know if you need anything! TJ 1 Quote Link to comment
SatoRich Posted June 11, 2020 Author Report Share Posted June 11, 2020 I'm in Fort Collins. I have a 720!! I think I'm good as far as parts for now. What year 720 do you have? Quote Link to comment
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