block or head gasket?

[2revup]

Thanks Josh Will give Rod a shout, fingers crossed its not cause if it is well i am really going to crack the block (i am trying to sell the car and this happens)


Brad

[TooF]

umm you realise mr2s have special bleeding procedures... it isnt just fill rev and done.

on the sw20 there are two bleed points you will need to connect a hose to, one on the radiator and one on the heater valve.

without bleeding the air from these you will cause off sorts of untold problems.

[2revup]

yeah i know they have sevral bleed points most under the body of the car (pain in the butt)... I was doing the dodgy, just to possibly rule that out as an issue, as i dont have the car at my place so time and access can be limiting unfortunatly.

[TooF]

no they have two.... one on the radiator and one one the heater valve. and obvisouly the filler neck/radiator cap in the engine bay.

fwiw: aw11's have a third on the thermostat housing as well.

[2revup]

Thanks Toof

[o_man_ra23]

o man, i dont understand how a plug can make it run lean, i understand about the gap of the plug, but know nothing on how a plug could make it run lean (unless maybe the plug wasnt firing, but then i would expect it not to idle)

The plug does not MAKE it run lean, but it will indicate if it is (an oxygen sensor can give false readings with age). Look at the plugs, they all should be a dark grey/black colour with a fine layer of carbon over them (or clean if they are fairly new). If they are light brown or white, you are running lean. This can in turn cause overheating.

To back up Joshtix's comments, there was noted a shift in the mould during Gen3 3S-GTE production which caused bores to become thin on one side. Notably, 2 and 3 seem to be the common faulting point. Toyota never released information on affected blocks.

[2revup]

AAH i am with you now I will check this also.
Thanks guys your a wealth of info.

[turbo4agte]

Im loosing you guys about the overheating and lean engine. I dont have any clue what the two have to do with anything other than cause of headgasket blowing. Before your car overheats from running lean you'd quicker blow the headgasket or pistons. Its similar to the theory that running low on oil can cause overheating. The engine would quicker throw a rod or spin a bearing than overheat from low oil.

Do a coolant system pressure test. If your loosing pressure tear apart the engine.

[o_man_ra23]

Not necessarily... I have dumped the entire cooling system in an 18RC before, and before doing any damage, it overheated to the stage where it wouldnt run

Similarly, if a cooling system is already being pushed (MR2 in summer with turbo boosting), then running lean can push it over the edge quicker than doing damage.

And... depending what type of oil you have been using, an engine can run for some time without oil in the sump... it will overheat due to the cooling effect the oil normally offers before throwing a rod.

So yeah, there are still a number of reasons a motor can overheat like this, and it is best to check all of them... starting with the ones you can check at home without pulling anything too far apart. Plugs can also indicate if water has been on them (if they are corroded then that is a sure sign)

[IN 05 NT]

easiest way to check for bhg related isues is a TEE KAY TEST, sas should have one also,

[turbo4agte]

Not necessarily... I have dumped the entire cooling system in an 18RC before, and before doing any damage, it overheated to the stage where it wouldnt run

Similarly, if a cooling system is already being pushed (MR2 in summer with turbo boosting), then running lean can push it over the edge quicker than doing damage.

And... depending what type of oil you have been using, an engine can run for some time without oil in the sump... it will overheat due to the cooling effect the oil normally offers before throwing a rod.

So yeah, there are still a number of reasons a motor can overheat like this, and it is best to check all of them... starting with the ones you can check at home without pulling anything too far apart. Plugs can also indicate if water has been on them (if they are corroded then that is a sure sign)

Hahaha... what Tom Foolery.

1. Your engine seized BECAUSE of overheating. It was just too quick for your gauge to even register.

2. As you mentioned it would have a bad cooling system to begin with. Its just not possible to overheat BECAUSE of running LEAN. It overheated because the cooling system wasn't working properly.

3. Before it overruns the cooling efficiency, it will overheat the oil. Point, blank, period, no other way of looking at it. And because of the oil temperature and lack of lubrication you will have no option except to throw a rod or spin a bearing. It cannot possibly overheat the coolant quicker than the oil itself.

[o_man_ra23]

1. the engine siezed after half an hour of driving with no coolant... it was getting more and more sluggish all the while. After letting it cool overnight, it then drove the 15 mins home without a hiccup. There was NO internal engine damage. So the engine overheated without blowing anything.

2. MR2 cooling systems can be at their limit without the cooling system having any problems. Its the nature of the car, what with having the motor at the back etc. Dont forget there is no airflow past an MR2 engine (nothing more than a light breeze anyways), so the oil system does not get the same cooling as a car with a front engine. So yeah, on a hot summer day, an MR2 CAN overheat because of running LEAN, especially when boost is being used.

3. ever heard of Slick50??

[turbo4agte]

1. The temperature gauge runs off of the coolant temperature sensor. If there is no coolant the gauge will read cool. The gas built up in the system (if any) isn't enough to drive the sensor.

2. The MR2's radiator is up front. I'll reiterate, there is something wrong with the cooling system itself. Whether that be the wrong thermostat for your climate, fan, radiator etc. A couple of years back a guy I went to school with put a GZE charger on an NA engine. It still did not overheat and Im almost sure the GZE radiator is bigger than NA. So if your MR2, or friends, etc.. is overheating, its because of that car. Its not an MR2 problem area.

3. Slick50 is regular high quality oil with a Slick50 tag on it. It still will not allow you to run the engine with little to no oil, and let the coolant overheat before the oil overheats and looses its viscosity.

In conclusion, if the car is overheating, diagnose the cooling system, not anything else. The problem will always lie in the cooling system. Other things may contribute to heat (oil, a/f, climate), but no cars are engineered on the "overheat threshold" so that any little change will cause overheating. So its likely your just overlooking something.

[TooF]

for the record both na and sc radiators are the same in aw11's infact it is even the same unit in aw10 with a 3ALU engine.

and the radiator in sw20s is the same for all sw20s, turbo or na

[o_man_ra23]

1. got nothing to do with the guage

2. see Toof's comment, and also 40 degrees plus days in summer in Aus

3. Slick50 is not an oil, its an additive. They put Slick50 in a car in aus, drove it round for a few hundred k's, then dropped the oil, and drove from somewhere in QLD to Darwin (couple of thousand kilometres in some of the hottest dusties climate in Aus) and back, without damaging the engine. Its proven effective, and not just manufacturer hype, it was recorded by independent parties also.