[hooki]

hi guys,

When i bought the sierra it always ran at a good temp and even did so during the hot summer days. Last week while going along the freeway for 5 mins it suddenly peaked up to the red on the temp gauge so i parked it up and let it cool down, i also checked the coolant levels and they were fine and radiator looks in good nic.

So yesterday i put in a new thermostat and put in new coolant and also ran radiator flush through it. Instead of being at the normal 2mm below half on the temp gauage it sat pretty much on half now. Heading out wheelin today after sitting on 100 for no longer then a few minutes it shot up to the red again. A mate behind me said that coolant was coming out of the car when driving and on closer inspection it was coming out of the overflow bottle. At this point the overflow was filled to the brim and the top of the radiator was low on coolant.

After letting it cool and topping the fluid back up that had come out of the over flow i was off. It heated back up but to just over half. Then when wheelin (very slow speeds...crawling) it sat just over half again.

Just wondering what you guys think is wrong It seems to realy heat up now and because it's my daily atm i need to get onto fixing it up.

[shep]

probably head gasket.

[laurie]

shep wrote:

probably head gasket.

sounds like it
check by running at idle from cold with the rad cap off
if bubbles come out when reving by hand on carb linkages
then you know

if it is you
could try irontight from repco might just get you out of trouble till
you can do a head reco ive used it in two other cars got me to work for a couple of weeks untill i got the vrs kit

also possible that you have a stuffed rad cap but not likely

[want33s]

Overheating at highway speeds usually means it isn't an airflow problem...
More likely a blocked radiator, faulty water pump or as suggested above, maybe a cracked head.

Jas.

[hooki]

hopefully it's not the head gasket. The sierra only has 140,000kms on it atm. The oil is still nice and golden aswell. I'll try what you guys said about the reving it from cold to see if there are any bubbles. Are there any other ways to check for a stuffed head gasket?

[hooki]

it also seems to only get realy hot when driving at about 90kmh for a little while.

[royce]

radiator externally blocked with mud
loose fan belt
blocked radiator internally

if it gets hot then blows coolant out its overheating, if it blows coolant then gets hot its a head gasket

[Rockhopper]

hooki wrote:

Are there any other ways to check for a stuffed head gasket?

A blown head gasket can either blow between the oil galleries and the water jackets, causing the oil and water to mix and give you that nice cappucino looking oil (and water), or it can blow between the water jackets and the combustion chambers of the cylinders which is sometimes a little harder to diagnose. Telltale signs you have a blown head gasket are the exhaust is a little wet and sometimes drips water around the tailpipe while the engine is warm and idling, the cooling system pressurises real quick after you start it up, and sometimes it will idle a little rough

[hooki]

royce wrote:

radiator externally blocked with mud
loose fan belt
blocked radiator internally

if it gets hot then blows coolant out its overheating, if it blows coolant then gets hot its a head gasket

seems to get hot then blows coolant out.

[hooki]

Rockhopper wrote:

hooki wrote:

Are there any other ways to check for a stuffed head gasket?

A blown head gasket can either blow between the oil galleries and the water jackets, causing the oil and water to mix and give you that nice cappucino looking oil (and water), or it can blow between the water jackets and the combustion chambers of the cylinders which is sometimes a little harder to diagnose. Telltale signs you have a blown head gasket are the exhaust is a little wet and sometimes drips water around the tailpipe while the engine is warm and idling, the cooling system pressurises real quick after you start it up, and sometimes it will idle a little rough

oil is still nice and clear/golden atm. Exhuast is bone dry. I might have to get a new radiator and change the water pump and go from there???

[royce]

providing the fins arent blocked up with something pull the rad and get it checked and cleaned before throwing new bits at it

[hooki]

will pull the rad out now and get it checked hopefully today. cheers royce.

[Built4thrashing]

are you runnig the stock fan or a thermo?
mine used to run hot with the thermo on it even at hwy speeds but when i put the fixed fan and shroud back on it ran cooler. thermo was restricting air.

Most likely is a blockage in the rad. or water pump or somethig restricting air into the rad.....Spotlights???

[hooki]

b4t, still running the stock fan and shroud atm. I do have some spotties but they are just some small lightforce 170's.

Radiator is currently being cleaned out at the radiator place and i will be picking it up tomorrow....hopefully it solves the issue.

[hooki]

radiator was 90% blocked. All cleaned out now and running like an ice block. cheers for the help people.

[Scrawny]

Cheaper than a head gasket!!

[Damo]

hooki wrote:

radiator was 90% blocked. All cleaned out now and running like an ice block. cheers for the help people.

This is pretty common in my experience.

You can save yourself some bucks pulling it out yourself and taking it into a rad shop too.

[something_else]

hopefully you did no damage to the head from getting it so hot