620 problems:(

[pepsx12]

hey im not on this forum much but my truck just started over heating but it doesnt seem like head gasket problems?

it takes a while for it to over heat and the fluid is still pretty clear?

it doesnt leak though iwas guessing it could be the radiator cap?

and i ahve a really bad leak from the oil censor thingy any help that i could get would really be apreciated

[motavated]

Give it to me and I will make it stop overheating!!!

 

Fan clutch? electric fan? manual fan? Thermostat degs? Fan shrow? Year? Motor size? Radiator size? How many cores does the radiator have? Etc etc etc..

 

Does the needle jump around alot?

 

We need more info.

[moparvwfreak]

could be a bad thermostat, clogged radiator, bad cap, almost anything.

[datzenmike]

Rad stays full?

 

No leaves/dirt or plastic bag stuck to the front?

 

Thermostat not opening fully? If an old thermostat, don't waste your time testing in boiling water. They're cheap get a good $12 one, throw old one away and use a new gasket. Don't use RTV, it looks un-professional and isn't needed. Besides, that shit breaks off inside and plugs rads and heaters. Don't use... bad.

 

If you have a clutch fan try to turn the blades by hand. They should feel stiff and will turn with some effort. You should not be able to spin it with light finger pressure. The fan should turn smoothly and there should be no other movement (up, down sideways) except rotating. Use a mirror and look on underside of pump body. There is a drain hole, is it wet or has it been leaking?

 

If overheating at idle:

Check idle mixture and reset. Running lean at idle will run hotter.

Check ignition timing. Retarded will run slightly hotter.

Do you have the fan shroud on it?

Is fan belt loose? Belt glazed and slippery?

Edited March 14, 2009 by datzenmike

[pepsx12]

alright thanks guys

im gonna try the thermostat

its a l20b

the coolant got a tiny bit off color brown but still doesnt have that hg smell

fans work and all but is really idling high

i adjust the timing and its still high checked for vaccum leaks and all but?

maybe a carb problem

hey motavated it would be really cool if you could help me out?

cuz this is my daily and canyon beater

i drive it about 50 miles there and back every day so im in need :(

[ezcruiser]

Other than what everyone else has mentioned, water in the oil and especially the thermostat you can try this if it doesn't help.

Do this while the truck is cold to -help- cross out the headgasket: take off the radiator cap and make sure the coolant system is full, while everything is cold! Then start the motor(with the cap off). Get out and go to the radiator. If coolant starts coming out of the radiator filler or starts bubbling up then you probably have blown gasket leaking air from the combustion chamber into a coolant port. This diagnosis takes like 5 minutes from start to finish and it will give you a little more peace of mind, if it's not blown. Good luck.

[banzai510(hainz)]

ahve a really bad leak from the oil censor thingy

 

Get a new one. Its the oil pressure sensor. They have a diaphrame that get get a hole and leak. get for your model vehicle as they are a 1/8 BSP thread(british)

 

Adjust the timming and Mixture

 

replace the stat to a 54 mm 160deg(its a Generic stat,not datsun listed) and see what happens.

 

http://www.olddatsuns.com/620tech.htm

[pepsx12]

alrihgt thanks guys it was a blown head gasket i had water bubbles all over my valve cover and milky stuff

thanks for all the info

[ezcruiser]

If you are going to replace it soon, get someone to take pictures of the replacement! I'm sure it would be greatly appreciated from all of us, especially the "how to" section! Even though Hainz has a video among other threads. Good Luck and keep us posted at least!!!

[datzenmike]

This bears saying.... be sure to lock the timing chain, (ask how or find out) or the tensioner will fall out and a simple h/g replacement turns into a nightmare.