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Discussion Starter #1
For some background info:

Maybe two weeks ago it iced over pretty good here in GA. The first day it iced over, my parents went out and cranked their cars to warm them up so they could get out. They warmed up fine and they drove them fine. I decided to warm up my car as well, since I had to go to work later that day. I cranked up my car (after breaking through ice to get to it!), let it warm up, and it ran fine. Then it started overheating. I turned it off, let it set, tried again, and it did the same. I caught a ride to work that day.

After things thawed out, I started driving it again and it drove fine. But within the week, it began to intermittently overheat while driving. The gauge would start going up, and sometimes it would completely return to normal, or sometimes it would keep climbing. Sometimes it wouldn't overheat all day.

I noticed about two days ago that when it got really hot, it would start a loud moaning from behind the block in the engine bay, which I am guessing is a bypass valve for releasing the pressure from overheating. Also, after it overheated and I parked it and turned it off, sometimes I could hear a slight gurgling coming from the back, which sounded like coolant getting past a hose. I checked the coolant, couldn't see the mark for full due to dirt, but filled up a good bit till it hit full. I then bled out the coolant and heating system and it's drove good for two days. Today it started doing it again.

Now, I am figuring that I may have cracked/popped a coolant hose going into the back of the block; how many and which coolant hoses run on the back of the motor? Any tips at getting to them before I take off and start workin on it, or any other ideas of what it may be? The car's not blowin white smoke, so I highly doubt it's a head gasket, and I can never really see any puddles under the car.


:confused: :mad2:
 

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There are 2 hoses (feed and return) for the turbo, a water bypass pipe that runs underneath the exhaust manifold from the outlet on the driver's side to the water pump, the HFH which branches off from the water bypass pipe to feed the oil cooler, and the HFHOE which is the return from the oil cooler to the water pump. The water bypass pipe is metal and would not burst. It is possible that the HFH or HFHOE could have burst but you would probably notice a leak or at least smell coolant burning. Do you see any white residue on the exhaust manifold or downpipe? If it's truly a leak, you'll see some signs (either a puddle on the ground or residue).

The gurgling you hear is the coolant boiling and flowing into the overflow tank.

How old is the radiator? Has it ever been replaced or "boiled" out? A headgasket is a possibility and it might be a good idea to have a combustion leak test done (not a leak-down test... A leak test using dyes that can detect combustion gases in the coolant). If it tests positive, it's a blown headgasket.

The first thing I'd do is thoroughly check all your hoses and also for leaks and signs of coolant residue on the engine. Then have the radiator tested. Then do the combustion leak test.
 

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Did you bleed the entire system? (i.e. all 4 or so drain bolts)

Also, what side would you consider the back of the engine? The side closer to the cabin or trunk.

The side closer to the cabin are what Nocera are referring to. There is a drain plug on the trunk side. There are a couple hoses and things that feed from the water neck on the driver side of the engine.... Just some things to check.
 

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my car did not blow white smoke, but i definetly had a blown headgasket. Go to the shop and do a leakdown on all the cylinders. see if air comes out of the coolant filler cap. if it does, time for a new headgasket! hose from hell is on the bottom back of the block under the turbo! have fun if you have to replace that.
 

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Discussion Starter #5
Alright, an update and some clarification:

Today I ran some errands earlier, and the car acted like it has been: sporadically overheating. I go home, park it for about an hour, then head out for work here at the MOG. Before I crank it, I top it off w/ more coolant and leave. I get to the mall (~10 miles) fine, then getting off the exit, after stopping at the stop light for ~3-4 minutes, the temp needle started climbing again. I stop, turn it off, let it cool, and head on to the mall. I get right in front of the mall, and it starts getting into the red again. I turn into the mall, take the first turn in, and it shoots down to normal! :mad2: Then, not even 100 feet later, it starts going red again, but by then I could scoot into a parking place and go in to work.

Triad - No, apparently I missed one of the bolts if there's that many. I'll check my manual and see where the other one or two are when I get home. Also, I call the "back" the turbo-side, the backside when you're facing the engine from the back of the car.

UMjaxman - I don't think it's a blown headgasket because my dad's car had one that I fixed; his constantly overheated, not intermittently fluctuating like mine does. Also, a major headgasket blow, from what I've seen, that would cause my symptoms, SHOULD also at least blow some noticeable white smoke.

The high moaning is coming from the back near the turbo, the gurgling sound is coming from the front, I believe near or under the intake! (checked that this morning as well)

And I bought this car to get me around while I fixed the other car.....MAN my luck w/ cars sucks! :cry:
 

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If there are no leaks, it's either the radiator, headgasket, or water pump.

A blown headgasket has different symptoms depending on where the headgasket failed. It will not necessarily cause the car to blow white smoke. When my headgasket was blown, I had the same problems you're having (temperature fluctuation). Check out the picture of my headgasket below. The crack and carbon on the sealing ring are signs that exhaust gases were escaping into the water jacket and thus boiling the coolant. Coolant was not getting into the combustion chamber and therefore I did not have any white smoke or other signs that the headgasket had failed. Do a combustion leak test as I recommended above.

 

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Discussion Starter #7
:eek: I will try checkin that then!

Well if it IS a blown headgasket, why would the car only overheat sporadically? It's almost like the thermostat isn't opening all the time....
 

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The water pump is driven by the timing belt. Therefore, at high rpms, there's more circulation than at low rpms. Differences in rpms will cause coolant in different parts of the system to heat up faster than other parts. This causes hotspots in the coolant cycle. It might also have to do with the fact that exhaust gases might not be escaping all the time (only intermittently).
 

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I had the same problem as nocera, no signs of white smoke. and couldnt find any leaking hoses. my mechanic did a simple leakdown test and air came gurgling out of the coolant filler. I suggest doing a LEAKDOWN TEST, it is very easy. I dont think a shop would charge much of anything, all they are doing is using the special equipment gauge on to a hose that puts compressed air into the cylinders. Close to a compresssion test, but not the same since u arent putting compressed air in a cylinder. My car overheated sporadically just like yours does. to be honest, everything your saying sounds exactly like what my car did. I even had the moaning thing that you did. It's from lack of coolant and my mr2 lost it's coolant very slowly. Just do a leakdown test and eliminate the possiblility of a blown headgasket
 

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You can also check to see if your heat starts to blow cold air - if it does it means that coolant is no longer flowing.
You may also want to check to see if coolant starts to blow out of the overflow - you can do this by putting a clean paper towel where the overflow bottle's rubber tube is.
Most of the time when a headgasket blows, coolants doesn't get into the combustion chamber - rather combustion gases over-pressurize the cooling system and coolant blows out of the overflow.
Make sure it is well bled, and full - then see what happens. Good luck!

Water Injection Kits
 

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Discussion Starter #12 (Edited)
Alright, well I'm worried good now.

It's acted great the past day or two, and it nearly broke down on me a few minutes ago. I noticed that lately it's also had a dead cylinder at startup after sitting overnight, but the cylinder starts firing after about 30 seconds of running or so. This morning I pulled the spark wires and figure out it's #4 (the far left one when looking from the trunk of the car) not firing, and that it is not sparking everytime it is supposed to (grounded wire to valve cover to see spark arc). I then drive to work.

It starts overheating today at the light in front of the mall, and I turn it off. I wait about 2 min's till the light turns green, crank it up, and it's got a dead cylinder and it's blowing huge amounts of white smoke from the engine. I kill it, let it sit till it's cooled some, crank it again, same thing, but I manage to get it into the mall, off the road, and coast it to my work. I noticed that when I got the RPM's up a little after first cranking it, it began to run normal again, just hot. I pop the engine lid and smoke is pouring from the bottom of the canister thing right underneath the radiator cap on the left side of the engine bay...what is that black canister? Also, coolant is sprayed a bit around that area, and leaked down below the overflow can.....

It's gonna be parked and I'll be checkin for the head gasket and thermostat tonight, and maybe hoses if I can get a working light hooked up.

I'm open to any advice, and wish me luck!
 

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The black canister is the charcoal canister. It's not related to the cooling system. Coolant sprayed in that area because it came out the vent tube of the overflow tank. Do the test for the headgasket first. If you test the thermostat, make sure you have a new gasket before putting it back on.
 

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Discussion Starter #14
Nocera said:
The black canister is the charcoal canister. It's not related to the cooling system. Coolant sprayed in that area because it came out the vent tube of the overflow tank. Do the test for the headgasket first. If you test the thermostat, make sure you have a new gasket before putting it back on.
That's what I thought it was, but wasn't sure; i'm a moron anyways, since I forgot I moved the overflow tube to right beside the canister just yesterday!

Oh well, gotta figure out how I'm gonna get it home from the mall now...
 

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headgasket :) everything happening the same as me except i blew a coolant hose first cause the coolant was being overpressurized and blew up a hose and cylinder #3 was my headgasket was blown.
 

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Discussion Starter #18
Well I guess I'm the bastard since mine's #4.... :)

Compression test came out fine - 190psi across +/- 5psi

I can't get ahold of a leakdown tester, so I can't test that yet. I used this junk to see if any combustion gasses were in the coolant, and it didn't show any.

But after driving some, my #4 spark plug will turn dark, unlike the other ashy grey healthy ones. After sitting for a day or two, the #4 plug was wet w/ coolant when I pulled it out!

I'm depressed now....I bought this car to be my reliable car while I fixed the other, and since I've bought it ~4 months ago, the alternator went out, and now the head gasket's blown! :sob:

So about how big of a job is it to swap in a new metal head gasket, assuming no machine work is necessary? Any recommendations? I have about two weeks of afternoons to get this fixed before my new block for my Honda comes in, and I begin starting on the build for it....
 

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Discussion Starter #20
Yeah, I've got the manual, but I figured there may be an easier way. I know droppin the motor ain't no fun either!

Blah, at this point I'd prob. pay someone to do it for me, since I don't have time, but the only shop around here that's well-trained in MR2's is Vick's Racing....and he's got quite a reputation on here!

Looks like fixing this will be my new project..... :sigh:
 
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