overheating m20 troubleshooting (updated)

[Pantless Spency]

Updated 5/9/11
got a new fan clutch put it in the fan pulls air hard now, no over heating at a sit still. but the car still gets dangerously hot. it seems to do fine in 4th gear at 2500 rpms, the heat gauge sits beetween 1/2 and 3/4's but when i put her into 5th and cruise around 2500 to 3000 rpms the guage sits over 3/4's and gets almost to the red mark... i have no idea why, and i can't get the air out of the system it just keeps pouring out. the guys at my local shop whom i somewhat trust are telling my dad that they think i have a leak somewhere in my head causing the over heating, but i thought i ruled it out by getting an HC test, but apparently the hc test isn't bullet proof? i have no idea.
so now i'm just thinking maybe i want to swap a later model m20 into my car. couldn't be to expensive, i just don't want to tear down this engine without any knowledge.
thoughts r3v?

[Pantless Spency]

blah i gave up on bleeding it,
i was thinking i should just drain the whole cooling system then fill it up again, anyone have any links to thread on how to do this??

[nickflic3]

Was the front end jacked up during all of this?

[Pantless Spency]

did the best i could, only have factory jack... so i drove my passenger side front end wheel onto the curb from my driveway inlet, then on the left side jacked up the car with the factory jack.
i'd say the front end was a good bit higher.

[nickflic3]

lol fosho, do what you gotta do :rofl:

[lolcantturn]

Multiple sessions and still the same amount of air spitting out?

Headgasket leak for sure.

Do a final bleed, heater on full blast, with the front end at least 1'' higher than the rear.
Close the bleed screw, rev that shit at 4k (wait i forgot you have an eta..fak) for like 10 seconds, open the bleed screw with the heater still on full blast. Let all that air get out. Squeeze on a few hoses. close bleed screw, drive around. If it's still overheating, and the same amount of air keeps coming out, ya gotsa get a new HG ;)

[Pantless Spency]

i'm gonna have the local shop run an HC test on it.
then i'll probably bring it to my friends in the mountains,
we were already gonna do a timing belt,
so now i'll take it to them and learn how to do timing and headgasket :)
maybe even a water pump

[Pantless Spency]

so i took the car to a local garage my parents have there cars worked on at, the guys were super nice did a free HC test for me so i can try to figure out why it's overheating.
its a euro place no worries, owner owns a super sweet 2002 that he uses for the track :)
basically the HC test cam back negative, no hydrocarbs? i have no idea where the air leak in my cooling system is coming from, also we found out i more than likely need to replace my fan clutch.
any suggestions on where the air may come from?

[Blackangusinc]

You should do a cooling system pressure test. If you don't have any leaks and your head gasket has been proven okay, then you need to keep bleeding. You might just have a bigazz bubble in there.

[Pantless Spency]

how do you do a cooling system pressure test??? lol.
and yeah i've bled it tons and tons :/ i'll keep trying tho!

[Danny]

Does it overheat when you drive it? Or just when its sitting still?

[Pantless Spency]

it hasn't over heated while moving YET. haha.
it has only overheated freeway side once since i bought it.
i'm gonna hopefully get insurance for it soon and a new fan clutch, then i'll swing on by.
in other good new for no reason the tach+ temp guage started working today for no reason. first time they've worked since i bought the car lol

[Blackangusinc]

How long have you had this car?

[7pilot]

Do the easy stuff first as it looks like the bleed screw of the cooling system is not sealing.....Loose maybe?;)

Unscrew the bolt and remove it.
check that the housing where the bolt goes is not cracked.
Clean the bolt with a wire brush, put some RTV on the threads of the bolt and wipe off most of it so there's a hint of RTV on the bolt threads. reinstall, top up with coolant and test.

If it still leaks in that area, you'll need to look more closely at the flange, and be ready to replace it. or reseal it at the gasket interfaces.

The overheating is because coolant leaks out, air gets in at the same site as the leak.
The system then cannot build pressure to raise the boiling point of the coolant/water.

m

[jlevie]

so i took the car to a local garage my parents have there cars worked on at, the guys were super nice did a free HC test for me so i can try to figure out why it's overheating.
its a euro place no worries, owner owns a super sweet 2002 that he uses for the track :)
basically the HC test cam back negative, no hydrocarbs? i have no idea where the air leak in my cooling system is coming from, also we found out i more than likely need to replace my fan clutch.
any suggestions on where the air may come from?

Unfortunately, a negative check for hydrocarbons in the coolant doesn't necessarily mean that there isn't a head gasket leak.

The simple test for a leaking head gasket is to completely bleed the cooling system, drive the car for a bit, and re-bleed. If bubbles never stop coming out when bleeding or if there is subsequent release of a good bit of air on a re-bleed, the head gasket is leaking. You really need to use the procedure below to completely bleed the system.

1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500rpm for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.