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The mkiv Supra Owners Club

N/a overheating..


Purity14

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Previous history of overheating..

Stopped using the car as i have others and im just getting round to fixing it..

 

So far :

 

Okay so radiator replaced (original was fubar) and new rad cap.

Compression test done and all figures are good.

Filled radiator with water for now to identify if problem still exists.

 

Ran the engine whilst continuing to fill radiator and the obvious bubbles appear and i keep filling.. Until full..

 

Bottom pipe from radiator takes a while to get hot but does get hot eventually..

 

Top hose is hot quite quickly.

 

Temp gauge is halfway normal.

 

Hot air in the car from matrix.

 

No water on the floor (core plugs)

 

Radiator cap still isn't fitted as i am trying to get air out still.. Suddenly water erupts high out of the radiator continually and doesn't seem to stop until i turn the engine off..

 

I put the rad cap on and started the car and it idled fine at normal temp..

 

I took the cap off from a distance after i turned off the car but still hot.. (I did it from a distance to be safe.. And it flew up in the air about 5 feet and i caught it. The radiator took another litre of water, must have been more air..

 

 

Just concerned about the water continually spewing up into the air repeatedly, like at least 6 inches into the air.

 

More bleeding required? Or is it something else?

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Guest Roger NE

Yes that is the best way to bleed the air out (even better if you keep squeezing the heater hose to pump the air out of the Heater Matrix - that's where it tends to gather)

 

HOWEVER . . . I regret to say that reapeatedly getting a load of bubbles out the top of the radiator (with the cap off) once it has fully warmed up is nearly always an indication that your Head Gasket has blown - even more so if you're getting torrents of water !

 

How do I know this? I'm a Mk3 Supra owner (on here because I'm about to fit a Mk4 engine in my car) . . . and the Mk3 Engines (7M-GE or GTE) blow head gaskets all the time !

 

I know it's pretty rare on the 2JZ engine (which is why I'm fitting one) . . . but I would bet money on that being your problem

 

Sorry mate

Edited by Roger NE (see edit history)
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Once the stat has opened and the heaters blowing nice and hot you should put the

rad cap back on and fill the expansion tank to the max line.

 

Then take it for a run keeping an eye the temp gauge and if alls well it should sit at normal

temp, then turn it off and leave to cool down, taking the cap off while its hot is a no no as it'll

be under pressure thus erupting out the rad like it did.

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Check the position of your top hose?

 

The N/A top hose is easy to fit with the wonk in it to be higher than the water level in the rad.

 

In this instance, the water you put in the rad can only feed the engine via the bottom hose and through the small bleed hole in the thermostat.

 

Running the engine during this inefficient fill, the stat will get hot and open letting water rush in and contact the uncooled head resulting with VOLCANO !

Edited by David P (see edit history)
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The car doesn't have an mot at the moment and I'm not insured on it, so i cant take it for a drive.

 

Im going to do a sniff test next week.

If its ok ill mot and see how it goes..

 

If the h/g has gone ill just ask keron for a engine swap, this engine has done 250k, but i think that the original time it overheated it must have blown the hg, the temp gauge had only just reached the top before i turned it off, so i was hoping for the best.. Oh well.

 

Hopefully if it passes an mot with a blown head gasket i can drive it halfway to kerons and then green flag the remainder of the way ;)

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As David has said

We had same problem with supra fluff recently and her dad kept saying it was head gasket

So we just kept bleading it with it facing up hill

Took a while but she recently drove from Cornwall to the 20th meet and back with no problems

I had a mk3 which the head gasket went and they were prone to it but the mkiv seems to be fine and rare

Just keep at it

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That aftermarket radiator has the top hose tail almost above the level of the bottom of the filler neck, I reckon if you reposition the hose about 20 degrees clockwise, it could cure it.

 

This can be checked by filling it cold as much as it takes, then push the hose lower in the middle, if the water level drops, the above will fix it unless you've caused further damage with heat expansion and sudden contraction.

Edited by David P (see edit history)
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Have you FUBARRED my old car?

 

Have you bled the system from the connection I installed on the top hose? I had a couple of issues with air locks but that fitting sorted them all.

 

I hope it isn't the HG but you have done some serious mileage in that car since I handed you the keys.

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Twisted it as described.. I see what you mean though.

Water doesnt go down when squeezing the bottom pipe.. Still stays at the neck of radiator..

 

Gonna let it warm up again now though and see..

 

If the compression of the engine was going into the water wouldnt it be volcanic out of an uncapped radiator all the time, even when cold?

 

Anyway ill report back in a sec

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Up to temp.. No volcanics!

Sat in the car pinched the overflow and filled to the brim.. Warm air in car and I'm watching the radiator water just wobbling at the neck of the radiator.

 

Thank you David, i think it was the symptoms you first described!

 

So Havard, she seems to be working fine.. :p

 

Im wanting it as a daily again, so next goal is a 333k then 500k :p

 

 

It wouldn't be the same on a different engine but who knows!

 

If it holds and doesn't overheat, polyurethane front lip and new alloys and the few spots of rust and little dents fixed with a full detail.. :)

 

Hopefully that will incentivise this car to behave :p

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Guest Roger NE
If the compression of the engine was going into the water wouldnt it be volcanic out of an uncapped radiator all the time, even when cold?

 

No . . . because it's only when everything has fully expanded that the Head Gasket starts leaking.

 

And in fact it won't ALWAYS do this when it reaches temperature . . you may find it only starts leaking again after you've been for a fast drive and got the engine really hot, and then sat in traffic (with no air flow).

 

The problem is that you rarely get a sudden TOTAL Head Gasket failure, it happens gradually. And when a Head Gasket BEGINS leaking it is nearly always intermittent . . . so people see the classic symptoms, but because doesn't do it next time they test it, they kid themselves that the engine's OK.

 

But what you normally find is this starts happening more and more frequently, until you eventually have catastropic HG failure, which can permanently damage the engine. (Apart from Head warpage, once coolant gets into the Oil you normally get big end bearing failure, certainly on the 7M engines)

 

I'm sorry if I'm full of Gloom and Doom, but I have seen this SO often on the Mk3 engines ! (My head gasket has just started to fail again, which is why I'm ditching my 7M and fitting a 2JZ)

 

My advice is get a sniffer check done. This tests whether exhaust gasses have got in the coolant - if they HAVE, the only way they're there is due to Head Gasket failure.

Edited by Roger NE (see edit history)
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But it WOULDN'T start spurting out like that unless his Head Gasket had failed

 

It would because without the cap on its not pressurising so if done for long enough the water will boil

just like it does in a kettle and it only has 1 place to come out which is the rad neck.

 

If the caps on it wont boil as long as the system isn't full of air but take the cap off in this situation and it will

launch out the rad neck because its now under pressure at around 1.1 bar depending what pressure rated cap

your using.

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Guest aspire

same as josh42, when we emptied my coolant and fitted temp sender in between top rad hose i filled up with toyota red started car with read cap on, on level ground, let warm up and topped up if needed, no problems at all

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