I have a question regarding ways to find out if my head gasket is blown on my 401 nailhead. When i first purchased the car it ran fine for short trips but one day i went 20 miles on the freeway and everything was fine until it sat at idle for a few minutes then had a cloud of steam cover the front of the car i pulled over and turn it off. i let it cool and realized that the performance fan that the guy put on was on backwards. it was pulling air towards the engine instead of pushing air to the radiator. long story short i drove it back home like it was and got home saftly with out changing the fan. I soon changed it and it seem fine as i went to the store close by. it sat for couple months. i tried to starting it last week and it got hot really quick. im stuck need some info to pin point the problem. if the head gasket is shot do i need to resurface the heads? need help!

I may be that you have a stuck thermostat, hopefully.

The fan should suck air through the radiator from the grill side. The fan should move the air in the same direction as the air naturally travels from the front of the car through the radiator around the engine and out through the underside of the engine bay.

Being as the previous owner changed the fan, the car probably has a history of running hot. If there is not a shroud around the fan, that can significantly reduce the effect of the fan. My first move would be to get the original fan and shroud back on the car, though that will probably not solve the problem.

it was pulling air towards the engine instead of pushing air to the radiator.

this is what it's supposed to do. if it pushed air towards the radiator, airflow through the radiator itself would come to a standstill as you were going down the road.

how old is your radiator? you may need a new one or to have the old one cored at the least.

in addition to the thermostat, check the 'vacuum' hose that goes from the radiator to the inlet of the water pump. there is supposed to be a coil steel spring in there to hold the hose open. if the hose has gotten soft or the spring has deteriorated, the water pump will suck the hose shut and you won't have any water flow.


so, check your thermostat and hoses first. they are cheapest and easiest to get too. after that, i would get the head gasket chem test and then take the radiator to a radiator shop to be checked out.





I have a question regarding ways to find out if my head gasket is blown

there is a diagnostic chemical test kit that will tell you if you have combustion gases in your radiator water. i know NAPA has them, don't know about the other parts stores. that's the simplest way.

it won't tell you if you've got a leak into an oil passage or a leak between the oil and water passage but those are fairly rare and have other diagnostic signs anyways.



if the head gasket is shot do i need to resurface the heads?

maybe so, maybe no. i'd just buy a gasket and try replacing it if the gasket is blown.

it wouldn't hurt to retorque the head that's doing 'fine' right now while you're at this..

Bring the car to normal temp and check your hoses to insure none are collapsing from the outside. This does not mean that one could not be collapsing from the inside, rare but it does happen.

To check for bad head gasket, look at the fluid in the radiator for oil and look at the dipstick for water. This will tell you if the car is exchanging fluids in any passages or head.

Before you take the car for a drive fill the radiator per specs for the car as well as the overflow container. Start the car and let it come to normal temp at idle. Check the overflow container for excessive fluid. This will indicate that you're getting a blow by on the gasket forcing water out of the radiator


No problem with the above, move on to check the thermostat. Bring the car to idle with the radiator cap off. When at normal operating temp look inside the radiator for good flow of fluid.

Thanks for the info ill check it out tommorow. Now thinking about it ill change the hoses and thermostat and have the radiator checked out. Thanks again I'll keep you posted.

and dont forget to put the fan back to how it was, the original installer had it correct----the airflow is from the front of the car to and through the rad then towards engine. Light a cigarette and put it in front of the rad with engine running---the smoke should go in towards the engine.

and dont forget to put the fan back to how it was, the original installer had it correct

actually, you can't change the direction of airflow by putting the fan on backwards. you'll still have the same angle of attack on the airfoil, you're just swapping the leading and trailing edges of the blade.

which, given that the rad fans are asymmetric, means that mounting it backwards will be less efficient but not that the air will actually flow the wrong direction.

if you want to actually reverse airflow you have to put on a reverse pitch fan, do a bunch of custom work to run a reverse rotation motor or somehow crossover the fan belt between the crank and fan pulleys. none of which you want to do anyways.

i agree though, presuming the fan was on correctly before, he wants to put it back that way.

I get what you mean.I don't remember if i told you thatI was an aftermarket fan. If he put a wrong fan how can i go about getting the correct fan?? Original or Aftermarket. Thanks again.

there are actually several fans that are factory "correct" for various engines. ranging from 5 to 7 or more blades.

if you have cooling issues, you normally want to run a fan with more blades although sometimes a well designed 5 or 6 blade fan will outperform a +7 blade fan.

first check and make certain that your fan clutch is working properly ( warm the car to operating temp, turn the engine OFF and try to turn the fan blade by hand, there should be a great deal of resistance ) if it's a clutch drive fan.

if it's not doing the job, then try to get one off of a BBC or large Caddy or other large displacement GM.

You probably need a larger radiator.

Well after some time i finally got to it. After reading all your input i purchased a fan with 7 blades from an unknown GM car at the Qualcom Auto Swap Meet in San Diego. It looked like it would fit but from closer inspection when i got home the holes were to far apart so i decided to make the hole into slots by drilling new hole closer to the existing ones filed them down to looke nice, before i put it on i flushed the raidiator and the engine, the water looke nasty but after running the water hose through it for some time it looked clear. I refilled it with antifreeze and water. The moment of truth, no more over heating at this point, i let it run for about an hour and a half and still no overheating the temp. stayed at normal operating temp:hurray:. I have couple questions regarding the fan are the fans balanced, did i screw it up by drilling it ? Do i need to drive the car to get the temp up or sitting at idle for an hour and a half good enough to find out if its going to overheat? Thanks for all your input.

Hi, don't really know if fans are balanced but I think so... If you've drilled with center right in place, no problem...
You should check engine temp while driving highway speed because the more the engine has to deliver horsepower at a same RPM, the hotter he gets ! However an hour an a half at idle seem a good sign.

Your problem could be as simple as needing a radiator cap - try squeezing the radiator hoses - f you can squeeze them, get a new radiator cap

pull the plugs,turn it over and look for antifreeze coming outta sparkplug holes.

crack the drain plug and see if there is water in the pan - it'll drain out first

there are onyl a couple engines that I know of that tuned counter clockwise - thos would be the only fans that - if erroroneously put on your engine, would push air toward the radiator - I don't think a parts house would sell something like that to a person that owned a Buick:clonk:
you would throw off the balance of the fan blade by drilling holes - unless you drill evenly spaced, equally removing the material around the hub.... look at the fan from the side as it is idlying - if outta balance, you will be able to see the wobble.

your test right now would be to do about 20 miles @ 65mph.... if it heats up - go buythat radiator cap
:waving: