[kritas]

Nearly 3 months ago my Sierra just clogged up with water in the oil and just died on me.

Here is a list of things I replaced and fixed since then:

Overhauled head(was dipped in some acid at the shop and came up sparkling new) with valve stem seals, buffed and cleaned valves, Camshaft pulley seal, and distributor housing seal.
Head and Rocker gaskets
New Sparkies
Thermostat
Water Pump
Alternator/WP belt
Timing belt
New Oil
New coolant

Fired the car up yesterday for the first time in three months, and yet.... It still overheats and dumps radiator fluid. I'm fucking stumped.
I pulled the thermostat out to see if it made a difference. It did not.

Can the car overheat if there is some sort of debris under the head gasket at all? It's not leaking from the head gasket, but it was a windy day when we replaced it so i'm not sure if i'm just being paranoid or not.

Any suggestions people? I'm looking to sell the car soon, but I refuse to sell it on to someone where it will have the same problems that I inherited it with.

[skyman]

Is it possible the head is cracked, or did you have it checked?

Any debris under the head gasket will make for a bad seal, and a leak.

Was the old headgasket bad, and if so where was it broken, or blown out?

[Reubs]

Have you now got an excessive amount of water exiting the exhaust, or water in the sump?

If not, did you check the radiators condition - could be the initial cause of your head gasket dramas and a problem is still there because it needs replacing?

[fordem]

Perhaps you should define the problem accurately - overheating is, fairly obviously, running at a higher temperature than it should, run it that way long enough and if the temperature gets high enough the coolant will boil.

A cracked head, block or defective head gasket can allow combustion pressures to leak into the cooling system and that pressure can force coolant out of the cooling system, which looks like an overheat & boil over, but it's not.

Looking at your post - you have a boil over symptom, which, as I have pointed out is not necessarily an over heat problem - how hot does the engine get? How long does it take to boil over? What are the conditions under which it boils over?

One thing missing from the list of parts changed is a radiator cap - a radiator cap with a damaged seal or a weak spring reduces the pressure within the system and allows the coolant to boil at a lower temparature than it should.

[kritas]

Head was checked for cracks, came back fine.
Not sure where the old head gasket blew out, how do you check?
If the thermo is reading hot, what difference would it make if the radiator cap spring is weak?

I'll replace it anyway as it's a cheap item, but as for the radiator and the head gasket I want to be 100% sure before I change it or have to remove the head again.

[royce]

how long does it take to start dumping coolant?

[BlueSuzy]

New radiator
Nice shroud
Nice fan

[kritas]

royce wrote:

how long does it take to start dumping coolant?

I'd say about 10 minutes.

[royce]

its not overheating, I doubt even if you went straight to full power from cold you could get it hot that fast!

run it from cold with the cap off and a big hole drilled in the thermostat so its not holding air and run it, if it starts spewing coolant before its up to temp then gets hot cause its empty something isnt sealed, block might be cracked or warped

[skyman]

Quote:

If the thermo is reading hot, what difference would it make if the radiator cap spring is weak?

When the coolant gets above boiling point in a closed pressurized system, it can't boil. This is why radiator caps have springs in them instead of an open vent, to prevent the coolant from boiling.

Caps have a spring in them to keep the coolant under pressure & prevent it from boiling. The spring also acts as a safety device, letting the coolant boil and evaporate before the system becomes over pressurized to the point of rupture.

If your spring is weak then the cap will open up prematurely, venting all your coolant before the engine reaches true overheating point.

Was this the first start/run that it dumped coolant,or did you refill it, and it dumped more? The reason I ask is that after you fill an empty system a lot of times they need to burp out air pockets. I usually park on slight hill and let it idle till warm with the cap off, then I rev the engine by hand until the thermostat opens and coolant starts flowing.

A lot of times (more often than not), it will start puking air, water and steam after the first few minutes. The I refill the radiator and let it warm up once more to make sure the air is out. (be careful of burns)

When does it overheat?
Only while driving?
Only under load?
Or will it overheat if left to idle for more than 10 minutes?

Can you see any evidence of corrosion or dirt in the radiator while looking in the cap?

hope it helps

[kritas]

it sat on around 5/8 full guage temp reading while idling. As soon as I started to reverse it our of my driveway to take it around the block, The temp guage rapidly went up.
I drove it back in straight away and removed the keys but the engine kept running at around 300-500 rpm until I released the clutch and it jerked forward and died.
this time no radiator fluid dumped but engine letting off slow amount of smoke.

Radiator cap seal looks well in tact, and spring has small amount of white crust build up, but seems to push in hard enough.

[hr]
Also i'll add that yesterday when I took it for a drive around it only overheated after a half hour drive but no signs of dumping coolant.

[skyman]

When you checked the level after it cooled down, how much was was missing?

Also if that is the only time you have run it you may want to try again, this time instead of pulling out of the block, give it a couple of revs and watch the gauge. It may just have been burping out the air.

I am thinking if that doesn't do it, your radiator is stuffed. To give you an idea of how well they work, when I installed my E-fan and had it on from the beginning the engine never got hot enough to register on the needle at idle. I had to rev it up a couple of times just to get the needle to move, and it would drop like a rock at stop signs.

Pull the cap and watch the radiator fluid. When the thermo opens you should see coolant flow by, slowly at first then faster as it gets hotter and the thermo fully opens. If the coolant overflows when the thermo opens, your radiator or a big line is plugged up.

[royce]

has your radiator been cleaned?

[kritas]

Nope, Should I just replace it and get a new rad cap, see if that helps?

[royce]

when an engine overheats sometimes the heat can dislodge all sorts of built up crap in the block and dump it in the radiator, clogging it

either a proper clean or a new one and cap is probably worth it, make sure your fan belt isnt slipping too

[kritas]

Fan Belt is brand new along with timing belt. It's gripping nicely compared to old one which didn't have any teeth left on it.

[kritas]

Replaced the radiator cap. So far so good. Gauge went a smidge past halfway, as I was hooning around in high revs trying to produce what happened before. this drive lasted around 25 minutes or so...

I also adjusted idle so it sits on around 1200rpm instead of 1700rpm now. I guess that would of helped it too.

[CompTruck]

drive it down the highway at the speed limit. thats where mine heats up

[kritas]

Too much traffic atm, peak hour sorta. Will test it out tomorrow.

[CompTruck]

yep. mine did it even in freezing cold weather. i thought that the highway speed blowing the cold air over the radiator would cool it.

apparently not. theory is that since the engine is doing quite a few revs at that speed the water pump is going fast and doesnt allow the water enough time in the radiator to cool properly.

i got mine pressure cleaned out. was good for the day 4bn and a highway drive to the track but when heading home that night after the car sitting more stuff must have come loose during the day and settled when the car was rested and reblocked it. so new radiator time

[Reubs]

kritas wrote:

I also adjusted idle so it sits on around 1200rpm instead of 1700rpm now. I guess that would of helped it too.

Is the choke blocked? There are 2 small hoses for the choke at the back of the carb - put your hand on them - are they both the same temperature?

[Reubs]

kritas wrote:

Gauge went a smidge past halfway

Does the guage stay in the 1 spot when at operating temp? My experience is the guage should be a fraction beneath halfway but as long as it sits in one place about halfway and never moves up or down it's ok.