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Discussion Starter · #1 ·
So I finished a head job recently on my cruze and I have hopped through a bunch of hurdles as is, but now it overheats! the coolant boils over into the revisor tank and overflows... great!

First thought of course is that I messed up the head gasket, but I got a new head, felpro gasket, new bolts and everything torqued/stretched to spec. When the car is cool no bubbles are coming from the tank, so I don’t think exhaust gas is getting in. oil/coolant seems clean. So I’m hoping that might not be the issue.

Next thing I’m thinking is the eBay water pump and/or thermostat are not doing their job. The “upper” coolant hose on the left side of the engine after the thermostat feels cool and soft to the touch. The right side “lower” hose next to the battery is hot. Maybe the water pump isn’t pushing? Or the thermostat is stuck closed?

Any thoughts would be greatly appreciated
 

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I would get an AC Delco thermostat and make sure you bleed the cooling system properly. Did you use the screw on the top passenger side of the radiator to get the air out?
 

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Discussion Starter · #5 ·
I would get an AC Delco thermostat and make sure you bleed the cooling system properly. Did you use the screw on the top passenger side of the radiator to get the air out?
Yes I did, a couple times now too, I will get a better thermostat.

also I’m thinking of getting a coolant reservoir and cap incase that’s not holding pressure causing the boiling point of the coolant to drop
 

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I doubt the rad cap will make that much difference.the thermostat is likely the best cheapest bet I would go there first . Do you have any bavkground on the initial failure ie why was the head replaced?
 

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Discussion Starter · #7 ·
I doubt the rad cap will make that much difference.the thermostat is likely the best cheapest bet I would go there first . Do you have any bavkground on the initial failure ie why was the head replaced?
Alright sounds good I’ll try that first and a bleed.

The plastic fitting to the return tank cracked & blew and it lost most of its water and reached upwards of 280° Before it was shut down. water was in the #4 cylinder a couple days later, so I cleaned it up and left it sitting for awhile after frustration.

Then when I got enough time, money & confidence I started the head gasket job DIY. I didn’t see any cracks in the original head, but I bought a new one to be safe. I flattened any high spots on the block with a flat sanding block, looked all good visually. I used a Felpro gasket. got an eBay water pump, thermostat, water inlets, & valve cover, to be on the safe side and replace them since I was already taking them off.

never had overheating issues before the day the HG blew.. only ground wire issues & PCV issues.
 

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Its is possible for a deck to warp but it doesnt happen that often in my experience. However I these engines were after my time with gm . So I cant say for sure .You can measure the deck with a straight edge and a feeler gauge and same with the head. There are obviossly issues with the head gaskets on these little engines. Pls let us know what you find
 

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could be air locked or a blockage somewhere. I assume you didn't remove the engine when you sanded the block, did you plug the ports up prior to cleaning/decking?

what temperature is your ect and rct(radiator coolant temp) reporting? does it only boil over when you drive or does it boil at idle when warmed up?

the hoses don't necessarily indicate a problem, if both hoses were hot, your radiator isn't doing it's job at cooling.

I would test the coolant for exhaust gases, it's quick and cheap.

turn the heat on full blast, if your coolant temp drops, that would indicate your water pump is pushing water.

if those check out, then I would replace the thermostat with an OEM
 

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We used to have a lot of problems woth sunfires and cavaliers after doing a head gadket they would always overheat if not bled properly. On the gmt 800 trucks there was a special bleeding procedure that was often required toxgetxthe air out many an engine was miss diagnosed as having a head gadket out when the updated bleeding procedure was used.It may be worth checking into thst justcto be sure
 

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We used to have a lot of problems woth sunfires and cavaliers after doing a head gadket they would always overheat if not bled properly. On the gmt 800 trucks there was a special bleeding procedure that was often required toxgetxthe air out many an engine was miss diagnosed as having a head gadket out when the updated bleeding procedure was used.It may be worth checking into thst justcto be sure

Yeah I ran into this on mine. I just squeezed the hose from the thermostat real hard repeatedly for a minutes after it runs for 5 minutes or so. To help prime the pump, seemed to work..
 

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Discussion Starter · #12 · (Edited)
could be air locked or a blockage somewhere. I assume you didn't remove the engine when you sanded the block, did you plug the ports up prior to cleaning/decking?

what temperature is your ect and rct(radiator coolant temp) reporting? does it only boil over when you drive or does it boil at idle when warmed up?

the hoses don't necessarily indicate a problem, if both hoses were hot, your radiator isn't doing it's job at cooling.

I would test the coolant for exhaust gases, it's quick and cheap.

turn the heat on full blast, if your coolant temp drops, that would indicate your water pump is pushing water.

if those check out, then I would replace the thermostat with an OEM
Yes the block and front cover stayed on, I tried to make it as easy as possible for myself, as this is the first time I have opened an engine that wasn’t on a motorcycle or boat. I vacuumed everything and everything was clean, I tried to be a perfectionist about it.

i can drive it fine around my neighborhood. It starts right up like new, but once it gets to about 200°+ it seems like it starts to boil. I Have been avoiding letting it go past 225°. I will run some tests with a temp gun most likely to see the real temps and not just the temp gauge reading.

turning on the heat does decrease the temp, and when it’s idling it won’t get hot enough to boil. If I let it idle with the heater on it will run all day without boiling over.

After an OEM thermo and a thorough bleed I will find time to get the car down to my mechanic as well. I’ll have him run the compression, leak down, coolant pressure, combustion leak, etc.
 

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Discussion Starter · #13 ·
We used to have a lot of problems woth sunfires and cavaliers after doing a head gadket they would always overheat if not bled properly. On the gmt 800 trucks there was a special bleeding procedure that was often required toxgetxthe air out many an engine was miss diagnosed as having a head gadket out when the updated bleeding procedure was used.It may be worth checking into thst justcto be sure
I will definitely look into that.
I told my friend about all this, he is an auto body/paint guy, but he works with people who have dealt with similar things. He tells me those guys always use some kind of purge pump to force coolant in and pushing through any air locks.
 

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Yes I have one it works very well and prevents this but does take a bit to to run we would only use it for the aforementioned problem children. After that initial overheat and big belch of air most settled right down. If it doesnt overheat or boil till you work the engine perhaps its the cooling fans not coming on. They useually come on at about 225-230 but by then youre already boiling over acording to youre gauge which by the way isnt very accurate. If the cap is working okthe coolant should not boil at 225 the pressure cap raises the boiling point of the coolant. This may be silly but have you blown some compressd air through the radiator. air/air and condensor or whatever is in front of the rad? That gives you some more things to check
 

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Discussion Starter · #15 ·
Yes I have one it works very well and prevents this but does take a bit to to run we would only use it for the aforementioned problem children. After that initial overheat and big belch of air most settled right down. If it doesnt overheat or boil till you work the engine perhaps its the cooling fans not coming on. They useually come on at about 225-230 but by then youre already boiling over acording to youre gauge which by the way isnt very accurate. If the cap is working okthe coolant should not boil at 225 the pressure cap raises the boiling point of the coolant. This may be silly but have you blown some compressd air through the radiator. air/air and condensor or whatever is in front of the rad? That gives you some more things to check
I can see the fans spinning and it looks like they’re doing their job, they’re not super loud either, they will also kick right on when you turn on the AC.

the reservoir cap; once it gets into that low 210-220 area it starts hissing and gushing air and coolant out of the little vent channel at the top. I can’t tell if it is releasing the excess pressure (more than 20psi), or if it’s not even holding the 20psi that I need to raise the boiling point.

the radiator is clean, and nothing is blocking airflow or anything like that. maybe a contributing factor is that I don’t have the heat shield on the turbo right now, doubt it gets that hot though.
 

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I can see the fans spinning and it looks like they’re doing their job, they’re not super loud either, they will also kick right on when you turn on the AC.

the reservoir cap; once it gets into that low 210-220 area it starts hissing and gushing air and coolant out of the little vent channel at the top. I can’t tell if it is releasing the excess pressure (more than 20psi), or if it’s not even holding the 20psi that I need to raise the boiling point.

the radiator is clean, and nothing is blocking airflow or anything like that. maybe a contributing factor is that I don’t have the heat shield on the turbo right now, doubt it gets that hot though.
how did you refill and bleed the system? how much coolant did it take? remove the vent screw on the radiator and barely reinstall it(just enough it holds itself in place). add 50/50 to the surge tank until coolant starts to come out of the radiator vent screw. tighten the vent screw and fill the tank up to the top. with the cap off... start the engine and add coolant if the level drops from my picture. reinstall the cap and run it at 2500 rpms for a minute or so...idle briefly and shut down / remove the cap and check the level. adjust to the cold fill line if necessary.

do this on level ground if possible.
 

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