98 gmc sierra blown head gasket or iac valve problem?

[Raider]

okay so two days ago was started my truck and its starting reving up and down at idle and when started to drive the truck was basically accerlating on its own. Made it home left it till today. Checked the antifreeze and there was none left no visible signs of a leak anywhere. and tried starting it and it would rev really high and then die. did this for a couple times till it stayed started but would still rev up and down while in park. not sure if its the iac valve. or if possibly my antifreeze leaked into my engine causing a blown head gasket? please help!

 

[jagtoes]

okay so two days ago was started my truck and its starting reving up and down at idle and when started to drive the truck was basically accerlating on its own. Made it home left it till today. Checked the antifreeze and there was none left no visible signs of a leak anywhere. and tried starting it and it would rev really high and then die. did this for a couple times till it stayed started but would still rev up and down while in park. not sure if its the iac valve. or if possibly my antifreeze leaked into my engine causing a blown head gasket? please help!

If the antifreeze went into the oil you would see it on the oil dip stick. So when you checked the oil is it overfilled? Do you have a CEL (check engine light) and if so take it to an autozone or similar place and find out what the codes are. If it were the IAC you would usually get a code. I would not worry about the head gasket until you see if the antifreeze is in the oil.

 

[Molson02536]

okay so two days ago was started my truck and its starting reving up and down at idle and when started to drive the truck was basically accerlating on its own. Made it home left it till today. Checked the antifreeze and there was none left no visible signs of a leak anywhere. and tried starting it and it would rev really high and then die. did this for a couple times till it stayed started but would still rev up and down while in park. not sure if its the iac valve. or if possibly my antifreeze leaked into my engine causing a blown head gasket? please help!

Check your engine oil for coolant mixing and clean your throttle body with throttle body cleaner. Make sure you clean the IAC also and at worst your may have to replace the IAC.

90% of the time the IAC is gummed up with carbon and cleaning the throttle body will fix it, make sure you use the whole can and good luck.

Keep us posted and good luck, if you do have mixing, try not run to leave the coolant mixed in with the oil to long. The coolant is corrosive to the crank bearing.

 

[Raider]

checked the oil and its like a creamy brown so seems as though the antifreeze leaked into it. also when i start it lots of white smoke comes out the tail pipe. blown head gasket? what should i do now? how much do you think it will cost to fix

 

[Molson02536]

checked the oil and its like a creamy brown so seems as though the antifreeze leaked into it. also when i start it lots of white smoke comes out the tail pipe. blown head gasket? what should i do now? how much do you think it will cost to fix

Being a 1998, you may want to look at getting a re-manufactured engine. The cost to repair your engine and replace the crank bearing ect would not cost much more then purchasing a reman.

The advantage of the Reman-engine is that it will have warranty, so if there is any issues with the engine through out the warranty period. Your covered any extra expense.

Good luck and call your local gm dealer for a engine swap or reputable garage.

 

[Raider]

how much will that cost?