i just installed a ms4 cam, so i had the front of the motor apart..i filled the coolant..drive around yaddayadda..park and shut the car car off, and coolant starts bubbling out of the resevoir. it does this until the coolant level is low enough not to overflow out of the resevoir.. temp does not get over 210 degrees either.HELP! thanks in advance.

 

Don't rely on these temp gauges, they do not read accurately. You have boiling over, so we know you have an issue.

Coolant boils over because of one thing....air in the system. So you either have a blown head gasket, a bad radiator cap, or a leak somewhere thats pissing out coolant while you are warmed up and pressurized and then sucks in air when it cools off after shutdown.

First thing....make damn sure you don't have air in the system.
-Radiator cap off when its dead COLD
-Start it when its dead COLD
-Stand there and wait for the t-stat to open (about 5-10 min) and see if the coolant starts to flow. If the level drops down, IMMEDIATELY top it off. Be ready with a running hose.
-Then...after the t-stat closed, wait again for it to open again. The n if the level drops down, top it off again.
****NOTE, if you're standing there and the temps are getting way high, and the t-stat is not opening, squeeze the upper and lower radiator hoses fully and rapidly constantly, that will move the coolant so it touches the t-stat and makes it open up. Don't just stand there and overheat. Because if the t-stat does not open...you have a huge air pocket on the engine side of the t-stat and it won't open.
***If your coolant level drops down a couple times, you probably found your problem. Go for a drive and see.***

If that doesn't work:

Make sure its topped off again.....then put the radiator cap back on, put the car on ramps, start it back up and let it warm all the way up to operating temp. Look for external leaks. THEN....if you see no leaks while its running, shut the engine "off" and watch it close for another 15-20 minutes, because it will get hotter and pressure will rise for about that long after shut down.

If that doesn't find the culprit (pinhole leak in a hose, bad water pump gasket, weep hole in water pump leaking, coolant pissing into the overflow tank, etc.).....get a new radiator cap and see if that fixes it.

If you still have the issue....you probably have a blown head gasket.

Bad fans won't cause coolant to boil over, unless of course you let it get to 300 degress. Of course, make sure they are coming on when you do the above procedure while you're standing there. Make sure they go into LOW "together" and then they should go into HIGH setting "together".



.

 

probably just a bad cap that lost it's seal when you took it off

 

Is it an lsx or ltx? Also i would start with the cap first. If its an ltx then bleed the system.

Check for leaks on the the radiator. I would also do a pressure test to see if the radiator holds any pressure.

Check the water pump make that it is not leaking.

 

its a ls motor..ive been still having this problem, and i was messing around with it today, and noticed the cooling fans would not turn on, but the temp stayed at 210..and coolant was very low..the low coolant light was on. so i topped it off..drove it and it bubbled out..messed around somemore, turned the ac on and the fans kicked on..hm, turned the ac off, fans turned off..unplugged the coolant temp sensor..and the fans kick on and everythings fine, maybe its just a bad temp sensor? i put a new rad. cap on and the problem continued..

 

i would also check the coolant hoses to make sure they are tight and for a small leak. i had a similar problem with my old 3.8. i couldnt find a leak anywhere until i pressure tested it at work and found a couple small drops coming from the bottom of the hose. the stock hose clamps tend to leak after you use them a couple times. id get some of the screw type clamps

may be the problem might not be but its an easy and free check

 

thanks for the input..looked at all the hoses and didnt see a drop coming from any of them..its just weird that my temp gauge NEVER ever read over 210 degrees..which is leading me to think it might be a bad sensor..(i hope) lol

 

Pressure test your radiator cap.

 

but would that keep the temp right at 210..even with the low coolant light on and steam coming out of the resevoir?

 

It could be 15 different things. The cap is a great place to start if you don't want to invest in pressure testing equipment. If your cap is the original, it will need to be replaced soon anyway, so its not really wasted money. The system is closed and pressurized and the cap is a key part of this. The seals wear out over time.

 

A bad temp sensor or gauge in addition to the cap.

 

replaced the temp sensor today and still same probs...


raplaced the cap a week ago and still having problems..

i noticed the cooling fans arent coming on..so i tested the relays with a gm tech 2..they all work, clicked on, turned the fans on when commanded..but they wont come on, on their own. havent had this prob til after the cam swap. i left the coolant temp sensor unplugged because that sends the pcm into default mode and keeps the fans on. i also used a block tester in the radiator, it basically "sucks" fumes from the radiator into a dye and thatll tell you if its seeing exhaust combustion..and that tested fine too.

poor economy>smokin a motor
will figure it out in due time. :\

 

is there a coolant temp fan switch on the block at all to tell the pcm when to turn the fans on? ive heard of this but am not sure.

 

The coolant sensor does that, but I understand that the PCM uses other inputs, like the defroster or AC on, to decide when to turn on the fans.

 

i feel like a moron..but here goes..maybe if someone does this as well, they will find this thread..the 2 lines that go to the top of the radiator..right by the fill..the one that comes from the crossover..and one that goes to the resevoir..were crossed..the resevoir was on bottom and heads line was on top..switched them..ran the car..got the bubbles out, fans turned on..everythings hunky dory.

 

So the correct position is the overflow resevoir on top connection and the heads line on the lower one?

 

correct..this is what happens when its 930 at night and your eagar for you your freshley cammed ls1 to start..

 

Dragging this one back from the grave.

Boy, I'm glad you posted what was happening to your car and what the problem was. I've been having this same issue with my 02 TA and, sure enough, the guy that did some work for me had swapped the steam line and overflow line.

Just swapped these back and letting it cool off to check levels.

 

lol, cool man, glad it helped!

 

This thread saved me today... Thanks!