I am boiling over in a 10min trip down the highway at like 65-70 mph. cant fig it out. Its a new aluminum rad h2o pump is 6mos old replaced the thermostat 2 times a 180 and a 195 which shold be fine it was 34 F here tis morning.the fan comes on with the ignition. I dont know what else to try. I have all new gaskets on the manifolds valve covers & oil pan and I flushed the radiatior last night since its not a new motor it has about 89,000mi on it. runs great power and everything. but it seems to be getting worse. help thnks


oh and no heat comes out of the heater either.

 

is there an air dam

 

What temperature are you reading, and could it be loosing pressure somehow, which will let it boil way before normal operating temperature.

If no heat is coming out of the heater, and you just fitted new inlet gaskets, it sounds like you may have the cooling blanks at the wrong end, or both ends of the heads.

Also very important you should get coolant around the heater on start up. If it can't circulate (maybe the hose is squashed) the pump can't work properly and circulate coolant up to the thermostat. The thermostat relies on the flow to the heater to get it's heat to open when needed.

With no actual flow to the thermostat, it stays closed even though the engine is getting hot. This will cause the problem you describe, boiling soon after start up, and no heat from the heater.

The cold weather makes it worse by overcoming conducted heat input to the thermostat.

If you get stuck, try a short run without the thermostat and see if the engine boils or not.

 

Thnks guys no I dont have ans air dam my driveway doenst like it. Destroyed it even. But my 305 ran cool with out it. I tried running it without the thermostat last night. it was still too hot. I mabey have and air pocket still? the hoses r fine. mabey I jusr have to take off the manifold and take a look. I dont think I messed up bur mabey I did goof. Ive heard the fuel filter can cause overheating??? Ill replace that too I guess. thnks any maore sugestions r greatly appriciated. and yes I have searched. and will continue to doi so while waiting for tother ideas.

 

Did it boil over though. If it just got too hot, but dodn't boil over it sounds like the blanks are not there in the inlet gasket.

It is coming back to me now.

I think the rear cooling outlet in the heads need blanking. This sends the coolant from the pump along the block to the rear of the block, then it goes up into the heads at the rear. The blanks force the coolant along to the front of the heads to cool them.

The heads have outlets into the valley pan at both ends and the valley pan passage connects both ends into the cooling system, so if the rear is not blanked off, the coolant flow takes the easy route into the valley pan and bypasses the heads.

Also in cold weather case the thermostat end gets no flow so it doesn't open.

When the thermostat is closed, almost all the coolant travels back along the coolant passage in the valley pan to the heater supply outlet. This also helps warm up the manifold and vaporize the fuel when the engine is otherwise cold.

When the thermostat opens, the flow splits between the radiator and the heater, with less flow to the heater than before, but with hotter coolant so the heater still works.

If the heater did not work at all, it sounds like maybe the gasket set needed blanks removed from one end to let the system flow, or something is blocking or squashing the heater pipes.

 

Ok great thnks for the detailed explination. Ill rip off the manifold this weekend and take a look see. Ill let u know how it went. thn ks again

 

Hey question 4 u u said u think the rear of the manifold needs blanking. r u sure? cause Im 99% sure thats where I put the blanks. please tell me for sure the books suck and I guess Ill call a mechanic to make sure as well. I have to rip it off anyway, cause Im leaking a little bit of oil from the back of it. so it may just be fukd up and floing into the motor a little or have a pressure leak or somthing. I dont know never had this rob with a manifold b4. thnks kev

 

Hi, The manuals are useless on this, but I think it is because there are so many engine versions. The biggest problem with th manual, is when thay say put it back like you took it out - what if it was in wrong??

I had the same problem with the first gasket set I got, blowing out the rear valley pan gasket, and letting oil leak. I bought the next set from NAPA, and they had a redesigned rubber gasket for the pan to stop the blow out problem, and a detailled explaination of the blanking arrangement.

If it is blanked properly and you have no heat from the heater, that makes the water pump suspect, or a blockage.

Before you rip off the inlet manifolds, and you say the thermostat is out, there is an easy test of the circuit. You need a quick reacting helper to work the ignition key you can't do it on your own, you must wear goggles - seriously. The engine MUST be cold. You have to keep clear of the fan.

Move the car outside, undo the hose from the heater return plug the pump end by fitting a bit of hose, fold the hose over and clamp it with a hose clip. Aim the heater return hose somewhere safe. Fire up the engine for about 3 seconds and shut it down. Coolant should shoot out. If it doesn't you need to find out why.

You can do the same with the top hose from the radiator, with the thermostat removed. If the pump and circuit are good, the radiator will empty in seconds, and you can't refill it for at least 15 minutes.

You can only do this once, otherwise you cook the engine. But as a last resort it shows if the circuit is flowing. And you need to drain the system anyway.

This is a risky procedure, because the coolant can go everywhere and, the fan and belts are right where you are working. You need goggles and really should not do it with anti freeze, unless you can be sure to clear it all up as it poisens animals.

You need the helper to start and stop the engine, because you can't get from the key to the hose and back again in time.

 

PS I am fairly sure it is the rear that needs blanking. The gasket set instructions though are the best way to check.

 

ok great thnks it does not flow really hard out of the upper radiator hose. the rad is new so that shouldnt be the prob. water pump is 6mos old and worked fine on the 305. I didnt do the heater core trick yet though. I guess Ill take off the intake what u thnkk? thnks again uve been very helpfull

 

May sound stupid but is the water pump rotation correct. Serpentine models have a reverse rotation pump.

 

thnks 4 the idea but no its not serp belt. its a 77 350 out of a truck just about have it off i needed a beer break my daughters hungery and my wife is on codine for a tooth ache the tooth is getting pulled tues so she s useless right now lol

 

yep I screwed up the intake gaskets were the wrong way around. now I just need to hget the alternater to stop making that horrible noise.

 

Hey that's great to hear you found a fixable problem. I hope it's OK from now. Those gaskets are too confusing. There is nothing about the blanks in any of the manuals that I can find yet.

Hope that tooth ache gets better.

 

Thnks and yeah when her tooth ache goes away, so will my headache thnks for all your help. its nice to see a new guy on the board that knows his stuff.