need help with an overheating issue

[Eagle_Adam]

I just picked up a 74 620 PU, i tore the motor down to the head gasket and had the head machined B/C of warp. I have put the motor back together and i still have an overheating issue. I let the truck run in my driveway for 10 - 15 min then it seems to overheat. So i replaced the thermostat first, still overheating. Next i took the radiator into a shop and had them do a power flush on the radiator. When i went to pick it up this morning the guy at the shop told me the flow had improved by over a third from when i first brought it in. So i put it all back together and im still having this issue. Ive checked the water pump by trying to spin it by hand(with the belt attached) it wont turn which i belive is a good sign that the water pump has not failed. The top and bottow radiator hoses are warm to the toutch after the engine has been running for a few minuits, and the fan is spinning and seems to be pulling good air thru the radiator. Im am not a complete novice when it come to engines but i am fairly new. Please does anybody know what else i can do to get my truck driveable again? And if anybody has an idea why i have clouds of white smoke coming out of my tailpipe that would be nice to know what to look for there too. I havent even put a whole mile on the car since i first bought it.

[Skib]

did you put the head back on right?

[DanielC]

A lot of white smoke means water in the exhaust. If you already have anti freeze in the radiator, the exhaust will have a sweet smell.

Check the ignition timing. Retarded timing will make an engine run hot.

[banzai510(hainz)]

if you have a heater intake manifold that has holes in the head for water passage make sure the intake lower bolts are tight so water cannot get sucked IN.

also make sure the lower rad hose does not collaspe (soft)

 

get another radiator cap

 

I drill a 1/8 or slightly bigger hole in the thermosstat plte to act as a slight bypass.

 

water pumps always work only the bearing goes out. I assume its a standard water pump NOT the clutch type. If clutch type then I CANNOT make a expert opinion on this.

 

 

if you ck the saprk plugs and see which plugs are nice and clean then you can narrow it down to where the leak is.

If plgs 2&3 are clean I assume its loose intake bolts or a intake gasket.

 

if this is a L20 its slightly possible the block is cracked between the head.

 

 

As danC said ck the timiming.

also you make sure the cam is timmed also.

 

olddatsuns.com

[Eagle_Adam]

Thanx for the advice guys, i will look into all of the above. I believe that i put the head back in correctly, torqued down the head bolts with correct pressure and in the correct order. I also had a friend of mine helping with the head and gasket, he knows more than i do. I just checked the plugs, they all look equaly clean and by clean i mean i replaced them when i was building up the engine so threy shouldnt be that dirty since i havent driven this bad boy more then a coupla hundred yards. :( I will look at the timing when my buddy dru comes over again. The lower andf upper radiator hoses are brand new and dont seem to be colapsing, and the radiator shop i went to hooked me up with a new cap this morning. o ya and this has the L18 engine in it.

[banzai510(hainz)]

WHAT i MEAN BY CLEAN PLUGS IS THE WATER GETS SUCKED IN LEAVING GHTE PLUGS A NICE CLEAN PORCELIN LOOK.

 

If it new plugs it harder to see iif the water is being sucked in.

 

 

good luck.

 

 

Im haveing proplems with my 521 water dissappearing right now. I swapped the cap and seeing how that does for now

[mike]

When you torqued the head bolts did you torque them in stages like the FSM recommends? Also were the threads in the block as well as on the head bolts spotless clean? Dirt and corrosion can cause improper torque readings which could allow the head gasket to leak. If it was all clean warm up the motor and retorque the head bolts to spec.

[datzenmike]

DO NOT torque on a warm motor. Yo won't get the correct clamping force. Only torque when it is cold.

[datzenmike]

And if anybody has an idea why i have clouds of white smoke coming out of my tailpipe that would be nice to know what to look for there too.

 

This says volumes. Almost for sure if you drove it for any time you would notice the water level dropping. Water is being run through the motor. Most likely the head gasket, possibly the intake as Hainz mentioned.

 

Preparation is everything, when changing a head gasket. Both surfaces should be shiny clean. Bolt threads wire brushed clean and lightly oiled. Threads in the block must also be spotlessly clean.

 

Assemble and use a torque wrench. Borrow or rent one and do it right.

 

I ALSO DELETED YOUR DOUBLE POST IN ENGINES

[Eagle_Adam]

Before the engine was reassembled both the engine block and freshly machined surface of the head were clean. My buddy dru did clean off all the head bolts with a bench grinder that had a wire wheel on it, as for the threads in the block we used a round small diameter plastic brush to clean them up and a shop vac to get all the debris out of the threads. I am going to open up the cam cover tomorrow and re torque the head bolts and check all the fittings on the exhaust manifold. I would put a bet on the install job of the manifold being at fault, some of the bolts that secure the manifold are tough to get to. I had a few comments made that the exhaust was slightly wet but i didn't get a "sweet" smell at all. We shall see, so far not too shabby for my first shot at restoring a truck. I love the character that this truck has! Thanx for all the help so far i will report back tomorrow.

[DanielC]

A plastic brush will not really clean out the threaded hole. Ideally you need a M10x1.5 thread chaser. Do not use a tap. It will remove too much metal. Another option is to get an extra head bolt, and grind a groove in one side of the threaded part, and use that to clean the threads. I then use a piece of 1/4 copper pipe on my air nozzle to blow the bolt hole out from the bottom.

When you are done cleaning the holes, screw the headbolts into each hole to make sure it goes in all the way, without binding on anything. Measure the distance between the bottom of the headbolt head, to the surface of the block, and make sure it is less than the thickness of the cylinder head, and cam tower for that headbolt. Do not forget the washer, when measuring. Some L engined used three different lengths of headbolts.

This is one of the many cases where taking time to measure everything, and doing it right the first time can save you a lot of time later, by not having to redo everything.

[banzai510(hainz)]

Eagle Adam

Let us know if the intake bolts fix it.

 

Earlier made exhaust manifolds(L16s) I can get my hand onder there with a box wrench. or maybe flip it over and try that.

Late L20 manifolds are even worse getting at those bolts.

 

I found I had one lower bolt missing yesterday. so Ill see if this was happening to my 521. But I had no white smoke. maybe a slow leak getting sucked in. Im hopeing. as I dont know what more than a head gasket.

[Eagle_Adam]

Ok so i will finaly be able to look at my truck again come tomorrow. Ill let u guys know.

[Buzzbomb]

A plastic brush will not really clean out the threaded hole. Ideally you need a M10x1.5 thread chaser. Do not use a tap. It will remove too much metal. Another option is to get an extra head bolt, and grind a groove in one side of the threaded part, and use that to clean the threads. I then use a piece of 1/4 copper pipe on my air nozzle to blow the bolt hole out from the bottom.

When you are done cleaning the holes, screw the headbolts into each hole to make sure it goes in all the way, without binding on anything. Measure the distance between the bottom of the headbolt head, to the surface of the block, and make sure it is less than the thickness of the cylinder head, and cam tower for that headbolt. Do not forget the washer, when measuring. Some L engined used three different lengths of headbolts.

This is one of the many cases where taking time to measure everything, and doing it right the first time can save you a lot of time later, by not having to redo everything.

 

^ That is GREAT advice...As someone who has done this job armed only with Ratsun knowledge when I started it, I will second everything in that post and every post in this thread.

 

I used an extra head bolt w/90* cut in it, as DanielC stated, and I'll tell you..A TON of junk came out of those holes, and they actually looked clean before doing it. My rule of thumb was to clean each hole until nothing came out, blow it out, and then check and clean each hole until the particular bolt for that hole could practically thread itself in. Afer that, I blew all the holes out with air, threaded/unthreaded the bolts again, and before putting the head gasket on, wiped the block and bottom of the head with lacquer thinner until spotlessly clean.

 

Maybe you've seen it in other threads, but a Sears 12mm shallow u-joint socket will be a huge help for a few of those intake bolts to make sure they are tight, as Hainz suggested. Well worth the $8, IMHO.

[Eagle_Adam]

Thank you to all who gave their input, i took my engine back apart to the head gasket. The entire gasket set from the the head up only cost $55. I cleaned and cleaned and then cleaned untill i felt it was useless to clean any more. As a direct result my truck is running! for the first time since i bought it. No white smoke and no over heating. The only issue i ran into was that once it was back together it was still saying it was overheating according to the dash gauge. So i got a new temp sending unit and all is well now. I cant thank you guys enough for the help so far, BUT now that i have been able to drive it i want to improve the breaks (the peddle goes almost to the ground) and it seems like the transmission doesn't want to engage in 1st gear. I have a new gasket and transmission filer coming in tomorrow so we shall see. Any advice on the above mentioned issued would be great. TGIF!

[datzenmike]

.... it seems like the transmission doesn't want to engage in 1st gear.

 

Do you mean you can't get the shifter into first or it's in first but you let the clutch out and nothing happens?

 

 

Bad brakes:

 

You have drums on all four wheels on your '74. Get them off the ground and adjust the star wheel located at the botton backside of the backing plate. There should be an oval rubber cover you have to take off. If they aren't seized you can adjust with a flat screw driver. Adjust untill you can just feel the brake when spinning the tire. Pump the brakes to center the shoes and check again.

 

Brake adjust is about 1/4 way down

[Eagle_Adam]

sorry, when i said it doesn't like first i forgot one major detail and thats that i have an auto. When i hit the gas it takes a second or two for first gear to kick in. I will look into the breaks tomorrow, thanx for the info

[Buzzbomb]

sorry, when i said it doesn't like first i forgot one major detail and thats that i have an auto. When i hit the gas it takes a second or two for first gear to kick in. I will look into the breaks tomorrow, thanx for the info

 

That's the way to do it...CLEAN until you feel it's pointless to continue, then do it once more for good measure :D .. Don't forget to recheck those head bolts after a a few starts and stops, and do it when the engine is cold.

 

As for your tranny...Simple things first. Is there enough fluid in there? I am not at all familiar with Datsun Auto trannys, but I am familiar with GM automatics, like TH350, and one of the first things you do if you a tranny is slow to engage or won't engage a gear is to make sure there is enough fluid in there. You'll eliminate this when you change your fluid, and you will also eliminate a plugged filter when you swap that out. If it continues, you'll have to go forward from there with it.

[Eagle_Adam]

Alrighty, so i changed the transmission fluid, filter, and pan gasket today to see if that was the issue. When i first looked at the transmission fluid it was a bit low prob about a quart. Now i have the new filter in and the pan back on with a new gasket. The transmission still doesn't really engage quick enough in first. The rest of the gears work great for a 35 year old car :) I haven't been able to look at the breaks yet, that shall have to wait until Monday.

[datzenmike]

Once DRIVE is selected it's in gear. When you give it the gas it should go. If it jerks suddenly it wasn't in gear. Possibly because the hydraulic pump isn't putting out enough pressure to hold it in gear. Low fluid will do this. Seeing as how you have changed it it should now work. Is it the correct dip stick? Is the idle set high enough?

[Eagle_Adam]

ill admit the first dipstick i grabbed was he wrong one :( However i quickly redeemed my self and got it right th second time. I even ran it around the block several times to make sure the fluid was warm. The fluid level is correct. How would i adjust the idle? i think this might be good to do regardless if it fixes the transmission issue or not.