My cooling system is insane. Overheating. WTF. (yes, I've searched).

[eisenfaust]

So a few days ago my 240 develops this overheating problem. The heater stopped working one morning, then the temperature spiked, then it fell back to normal and heat came back. It was fine for the rest of the day.

The next day, it starts running a steady high temperature (one tick or so away from the top tick, but not at the H), and I pull over and have a look. Sure enough coolant is pissing out my water pump. So I get a new water pump and have a go at it.

This morning I replace the water pump. Bleed the system (Get a few good burps out of it), and drive off. The radiator develops a crack at the upper coolant hose neck area. >_<

So I try patching it which of course doesnt work, so I get a new radiator.

New radiator goes in just fine. Bleed the system again, cars idling nice and cool, go for a test drive. Car overheats again. Intermittent heater function. LOTS of air bubbles.

Take the motorcycle and go get a new thermostat, because I notice the lower hose is totally cold, as is the radiator itself.

THis time I totally drain the coolant. Engine block, heater c***, lower hose, radiator drain plug, the works.

I pull the old thermostat (which was stuck in the "sprung" position. I could move the valve by pushing against the spring. The new one was rigid.), put a new one in (jiggle valve up, nice bead of sealant, valve into the block), refill, bleed for 20 minutes (no burps this time, but the heater worked instantly)

So far today I have replaced my:

Water pump (definitely working, lots of water pressure) Things are a lot like this thread: zerothread/251785 but I dont think my impeller is slipping. I get great fountains of water every time I rev the engine.

Radiator (seems to be flowing fine. it drained VERY fast when I pulled the drain plug)

Thermostat (which I suppose I should pull and test. Is the valve supposed to move in or out when it gets hot?)

I dont know WTF to do next. I've bled the system as well as I know how to do. I ran it for a solid 20 minutes, radiator cap off and bleed valve open, on ramps, and it didnt burp. After I drove it it was forcing plenty of water into the overflow tank.

The heating system is working fine now. But the lower radiator hose never heats up.

Am I supposed to do something to the thermostat before I install it? I installed it per the FSM, jiggle valve up, RTV silicone for a gasket (no leaks, yay).

I dont know WTF to do.

I'd suspect a blown head gasket, but the engine runs great, there's no white smoke in my exhaust, no contamination in my oil, and the coolant system can pull a vaccuum to draw fluid from the overflow.

Do I need to let it heat and cool in cycles when it bleeds? Shouldnt the thermostat be opening once the temperature spikes? >_<

Any suggestions at all?

[eisenfaust]

For what its worth, I just tested my OLD thermostat on the stove. It works perfectly. Starts opening at 170 degrees. Fully open around 200, closes again no problem.

[EviL inside]

do a cold compression check, then go back to the water pump.

you saw what happened to mine. it would flow at idle, but you raise the RPM's and it would slip. it was actually being held onto the shaft somewhat by the design of the cavity it sits in, but slipped like crazy. seriously, it's so easy to change the pump, go ahead and try it.

[Florida240sx]

Only thing would be something clogging the system, But it shouldn't of gotten past the thermostat...I found a 8" long piece of gasket maker floating around in my engine block where the water pump goes... But I ran with no thermostat after the original got stuck....

[eisenfaust]

Okay, here's my thinking.

The old thermostat works. Therefore it just wasnt getting any hot water, it never opened, and the car overheated because it effectively had no radiator.

I suppose it could be a water pump thing. Is there any way to tell if its slipping if I remove it? Hold onto the pully mating face with a wrench and try to spin the impeller?

My other thought is a clog somewhere between the water pump and the thermo housing. The metal housing itself isnt even getting warm.

Could there be a massive air bubble back there?

Tomorrow I'm going to pull the water pump and thermostat and look for a clog. THen I'm going to try the asprin trick and see if opening the thermostat does the job and lets a big air bubble out. Dont see why it would, but stranger things have happened.

If therei s a clog, what would be the best way to flush it out?

[ajgiorgi]

Did you bleed it from the thermostat housing? My thermostat wouldn't open after I replaced it. Make sure the jiggle valve is up when you install. $100 lesson courtesy of the radiator shop in Mountain View. Now mine to share! yay!

Anthony

[eisenfaust]

How exactly would I bleed it from the thermostat housing? The pipe that goes from there, back under the manifold, goes directly to the bleed screw on the top of the engine.

My mechanic is thinking blown head gasket. I'm not sure. ;-\

[Chukidori]

If your getting FOUNTAINS of water when you rev the engine..thats unusual.....

id agree with blown headgasket...ive heard the symptoms are very similar to what your discribing...if the water is "flowing" it shouldnt be shooting out of the cap AT ALL but rather flowing real fast like a river along the inside of the radiator it shouldnt touch the top of the cap.

A "fountain" of water sounds like gasses from the combustion chamber are leaking into the cooling system when you rev it up real high. That would explain the geyser...but if its leaking bad enough to do that..you should also be seeing some steam in the exhaust.


Modified by Chukidori at 4:12 PM 6/15/2007

[EviL inside]

If your getting FOUNTAINS of water when you rev the engine..thats unusual.....

id agree with blown headgasket...ive heard the symptoms are very similar to what your discribing...if the water is "flowing" it shouldnt be shooting out of the cap AT ALL but rather flowing real fast like a river along the inside of the radiator it shouldnt touch the top of the cap.

A "fountain" of water sounds like gasses from the combustion chamber are leaking into the cooling system when you rev it up real high. That would explain the geyser...but if its leaking bad enough to do that..you should also be seeing some steam in the exhaust.

Modified by Chukidori at 4:12 PM 6/15/2007

mine did that too. if i revved it while bleeding, coolant would splash all over the place, shooting out of the radiator. no blown headgasket.

just pull the damn pump. hold the pulley in one hand, and the impeller in the other. twist.

[mikefromtjs]

Listen to me bro I had the SAME EXACT THING HAPPEN TO ME. THE SAME THING.I hate to tell you this but for sure its a cracked head gaset.My car used to overheat like cazy so I took it into my mechanic. He thought it woud be a simple therm. problem.He got a new thermostat from nissan and put it in. Didn't work.We had the flow checked on the radiator... Just fine.He pulled the water pump... Just fine.

I couldnt believe my car coud have a cracked head gasket either it runs really strong. It really pulls hard. Thing IS THAT A CRACKED HEAD GASKET WON'T SHOW UP ON A COMPRESSION TEST. However, if too many fumes get into the system it causes massive overheating.

Tell me this...Does your car...overheat at night?overheat with no traffic?Overheat with steady speed?

If it doesn't overheat in those circumstances then you have the same poblem as me... cracked head gasket.The reason I say cracked head gasket instead of blownis because compression is still strong.

[Enigma_240sx]

That is pretty much what mine did tonight. I was driving (smelled coolant) then when i looked my temp shot up to H. When I pulled in to the yard I popped my hood and there was coolant/ strong spray of steam coming from the rear of the motor, mid-block passenger side...any help?

[Chukidori]

mine did that too. if i revved it while bleeding, coolant would splash all over the place, shooting out of the radiator. no blown headgasket.

just pull the damn pump. hold the pulley in one hand, and the impeller in the other. twist.

well he said a FOUNTAIN.

splashing is different than a "fountain".

[EviL inside]

do a cold compression check, then go back to the water pump.

have you done a compression check yet?

[youngun21a]

Have the same problem,bottom hose cold upper hot,change the thermostat same thing cold and hot hose,so I thought it was the thermostat,hear some termo are defective so I bought two different termo, tryied them both same thing,water pump work,no white smoke,run with out thermo does not overheat till and hour or so in stop and go traffic.and the water level sims low,but don't see water under car or heater core, Can't run it forever with out thermo. I notice something the heater core top hose is hot and the bottom warm,think there is a flow problem??

[wa-chiss]

has anyone thought about the radiator cap?

[EXCURSUS]

I'm no mechanic, but I recently experienced a similar problem. I had the radiator flushed, bought a new cap, new hoses, water pump, thermostat...you name it. Ended up being the fan clutch. My car doesn't have air conditioning, so I just rigged up the old electric fan and it was enough extra air flow to keep the engine cool, hehe. It's pretty ghetto rigged, but it works for now.

[JdrifterCA]

mix more water to raise the boiling points? lolz just a random thought. OR U CAN ONLY DRIVE AT NIGHT!!! IT REALLY MAKES A DIFFERENTs.

[180fan]

obvious troll is obvious.

Adding water does not raise boiling points.

[rogoman]

I pull the old thermostat (which was stuck in the "sprung" position. I could move the valve by pushing against the spring. The new one was rigid.), put a new one in (jiggle valve up, nice bead of sealant, valve into the block), refill, bleed for 20 minutes (no burps this time, but the heater worked instantly)

If you bought an AFTERMARKET PIECE OF JUNK thermostat, then that could most likely be your problem. Buy a new OEM unit from a Nissan dealer. Make sure the 'steam hole' is at the top when installing.

[ZOOMIGUEL]

deff not a blown head gasket,

if i were you id take out my thermostat ( since it is summer ) and you dont need it therefore it will let coolant be in engine >_<

then i would drain the radiator and fill it again, wait for a burp or two.if that not the prob... let me knowthough im having a similar problem but i have fixed mine bit by bit

[574-240sx]

When its cold after it has sat over night. Pop off the radiator cap if you get bubbles its a blown headgasket. It sounds like a blown headgasket or some air bubbles in the system.

[EviL inside]

did you ever do a COMPRESSION CHECK?

[574-240sx]

Sorry I change my online diagnosis. I going to say clogged heater core.