ztim

I put a new water pump on the 307 engine. I also put on a new radiator cap and flushed the radiator again refilling the radiator with new coolant. It had been working fine around town and to some places I go to about ten miles away.

Today I had to drive about 45 miles and when I turned the engine off, it started to boil over through the resivoir. It is better than before with the new water pump, but not as good as it should be. Help! and Thanks!

Oldsguy

Thermostat stuck closed, or air pocket in block could cause it.

ztim

I just got home. Same distance and this time it did not overheat! Must be a pocket of air in the block. If I remove the hoses and flushed it, would that take care of it?

joe_padavano

My 307 is the only Olds that I've had a problem getting the air out of the cooling system. I've found that the best way is to park the car in a nose-up location and fill the radiator as best you can. Run the engine and keep the reservoir full to the top. Once you shut off and the radiator cools down, it will suck additional coolant out of the reservoir. It will take a few cycles like this to fully bleed the air out of the system.

67htc

My '67 330 did the same thing after I put it together from having the heads redone. I drove it into town, (about 7 miles), shut it off, and it puked all over the concrete apron at the gas station. I let it cool down, refilled the radiator, and it has not reoccurred since.

ztim

It has to be the timing. I pulled my boat last night and it overheated like a son of a gun. Since the car still wants to diesel once in a while, it has to be the timing. A less expensive timing light is around $50. I will see if I can borrow one otherwise I will have to take it to a shop.

Oldsguy

Oh man, seriously, you should buy yourself a timing light. With an older car that has points type distributor, every time you do a complete tune-up you will need it. It is worth it.

millwrightrice

Don't forget about the thermal clutch on your fan if you have one.This really can cause headaches if you forget about it.If you do not feel air rushing in compartment at idle the fan s not doing its job

texasred

Dial-back light, if you can afford it...and a dwell/tach....and a vacuum gauge...

C.J.

ztim

I would eventually like to get one, but for right now I need to just borrow. The cheapest I have seen for the light is around $50.

texasred

Been there....borrowed that!

Keep an eye on the Sears ads. They seem to put a "tune up" kit on sale every month or two. You can get 'em from JC Whitney, but ya get what ya pay for.

C.J.

Omicron

Gawd I can remember finding those at the grocery store in the little puddle of auto parts they inevitibly have, but no more. Used to have a really nice one that I finally gave away years ago as I had no use for it. D'oh! But yeah, definitely sounds like a timing issue.

ztim

I still have had no luck in finding a light other than the expensive ones. Just as well. I tried finding the marks around the flywheel and the water pump and stuff is in the way. I don't have to move all that. Do I?

Oldsguy

you should be able to see the timing marker if you get down low enough near the front of the driver's side fender and look at the front of the engine below the alternator above the power steering pump. At the right angle it is visible. Of course with a lot of crud and dirt and if you don't know what you are exactly looking for it would be harder. To be short, no you don't have to move anything to see the timing mark on the flywheel and the marker on the front of the timing cover.

Redog

Will this work with the 350 Rocket too? I have to change out the heater core and want to make sure I get all the air out

joe_padavano

Yes. This works with any engine that has a modern radiator pressure cap and overflow tank. The cap is designed to allow the air to escape when hot and then to draw the extra coolant back in from the overflow tank when cool.

Lady72nRob71

I just redid the cooling system on my 72 350 and Joe is right.
Withthe the engine off, fill the radiator to the top. Then start the engine and lots of air will be purged out. Withthe engine running (not hot!) I added coolant until it was almost to the top and shut it off. I topped off the radiator and then filled the coolant bottle to the full cold mark.
Worked like a charm...

ZTIM, I assume your 307 is computer controlled. Read through this link about 307 overheating, setting timing, tips, tricks, etc.
http://tlentz.oldsgmail.com/howto.html
Seeing the timing marks on my 86's 307 is challenging but can be done. First, i would find the mark on the crank pulley / harmonic damper and mark it with liquid paper or model paint. Makes it easier to see.

When it is overheated and idling, the fan SHOULD be blowing LOTS of hot air. If it is just a little, the fan clutch is shot. I had the same problem.

Texascarnut

Yup, it will work every time. If you are impatient you may also be able to install a "burp" valve somewhere on the intake if there is a plug into a water passage anywhere near the thermostat housing. Many engines manufactured after the mid 1980's had factory "burp" valves on them.

Texascarnut

Getting back to ztim's original problem; flushing the radiator does not insure there is not a problem with the radiator. It is not uncommon for radiator tubes to become clogged. This is particularly true with radiators with aluminum tubes where tap water has been put into the cooling system. The cheap way to figure this out is to measure the amount of coolant it takes to fill the cooling system verses the cooling system capacity specs. (note: there will always be some coolant that will remain in the lower block unless it is drained separately).

There is also the potential of both upper and lower radiator hoses needing to be replaced. An old lower hose can be sucked flat to the point of restricting coolant flow though it may look great when the engine is cold and not running.

Timing can be an issue but without dieseling being an issue or fuel consumption being outrageous it is unlikely.