If your car is overheating it can be due to many things

When people hear 7mgte... they immediately think they have a blown head gasket.. this is not always the case

it's a good idea to run through a few other things before you think the worst

overheating generally only happens when stopped in traffic, on the highway the temp comes back down but here's a few things to check anyhow :)

check your water pump
your viscous fan
make sure your thermostat is opening properly (if in doubt, just buy another one they're only $15odd nzd)
make sure your radiator isn't blocked
check for any split hoses
check for any water leaks
your heater core might have air bubbles in it so you need to burp your cooling system (best way i found is jack her up so the radiator is at the highest point... make sure the engine is warm at this point and start her, get the hose or bottles of water and start topping her up... she might bubble a bit while air locks are being cleared, once the bubbles stop cap her up and set her back on the ground)

if none of this has solved your problem get a "TK head check" and check for exhaust gasses in the cooling system... if the blue liquid changes to a greeny colour then it's possible there's exhaust gasses in the water, if it turns yellow there's a definite sign you have exhaust gasses ( i think thats the right colours... it will say so on the instructions anyhow )
if it does confirm exhaust gasses in your water you have absolutely blown your head gasket so get ready to pay out :P

also check your oil, make sure it's not discoloured at all.. milky or chocolate milkshake... if this is the case... you have blown your head gasket or you may have a crack in the block or head... you need to strip her down and get the engine reconditioner to check this for you... usually you can tell by looking at the head gasket.. if the head gasket has definite signs of blowing between galleries usually you don't need to worry bout cracks but you still need to get it all checked.... last thing you want is to buy all the parts, slap her together only to have it happen again

well that's all i have to add for now.... anyone else like to add :)

very good report
must confess most probs seem to derive from one or more of the faults youve given .often then ending up as gasket failure,or worse.
Never trust a new t/stat or gauge when circulation probs exist + new t/stats dont always work .They sometimes need help to open for the first time. ;)

ahhh yes lol, did i forget to mention the thermostat thing... i think sometimes it's a good idea to maybe just drill a 1/4 hole in the top by the little toggle

i figure if it's really really bad and the info isn't up above then they can email me hehe ;)

I ha a gurgling sound in the engine when revving away so I took it to the local shop. I said about needing the system burping and about removing the thermostat and drilling a hole in to ease the problem and they initially agreed.

They split the thermostat housing away and there was no thermostat fitted at all.

They did a HG check and said it was OK. They did not have any thoughts apart from the system needed burping once and for all.

Does anyone have any thoughts.

Thanks

does you car overheat with no thermostat?... i would stick a new one in.. burp it... and make sure your radiator isn't blocked... to hear gurgling in the dash you definitely have air bubbles there somewhere

A little bit more information for you all to ponder. I collected the car this afternoon from the shop and had a really good report on the engine etc. The shop said they had test driven the car and she was still warm so I guess that was true. Within a mile of leaving the car started to overheat and I pulled in and stopped just as the needle touched the red. I just could not get in any sooner because of the road and it would have been suicide to stop.

I had the shop come out and their mechanic let it cool off, topped it up with about 1.75l water from a 2 litre bottle started her fine and drove back.

He took her out for a test drive of 8 miles and she was fine. Got her back to the shop and let her sit with the heater fan off and engine on tickover. The secondary fans came on OK and she behaved as normal.

I have let the shop keep her for a few more days as I want them to do a few cold starts and run ups to see if this happens again.

My own feeling is that they forgot to connect the fan sensor but i was wondering if there was any chance of any damage especially after such a good report on the engine beforehand.

Many thanks to anyone who thinks about this and makes a comment.

I have spent the last few hours really thinking about this.
The car was ready for a new timing belt and had slooshing water noises behind the dash. I sent it into the shop for a new timing belt, water pump check and to check the thermostat and drill a venting hole in the thermostat if needed.
The first thing the shop did was a test on HG reported HG=OK. On that basis they did the belt and thermostat and refilled with new coolant mix. I dont know if they burped the system with the nose raised but I did mention this to them beforehand.

Within a mile of starting (warm start) the temp started to climb too fast and too high and I stopped as soon as was safe.

This all begs the question of how did the air get into the system in the first place so I heard the slooshing sound. Could it have been sucked back from the expansion tank? Is the HG blown even if the shop says otherwise.

Why would the engine overheat. The shop said they had a long test drive prior to me taking it away. I drove steadily for two minutes and nearly cooked it. The danger is that I got it too hot and have destroyed the HG and/or twisted the head. Bloody Hell.

When the car was back at the shop the car showed no signs of overheating and behaved normally.

I am wondering if I should just bite the bullet and put in a new HG. Do I have any arguement with the shop. I have used the car for about 10 days (200 miles since purchase) and not lost any coolant during that time. I really think the HG was OK.

Thats about all I can add for now. Any thoughts would be useful so many thanks in advance.

seems like you're having a bit of fun then hehe

when does it start overheating.... hills... traffic... highway.. which?
does your heater blow hot air?
how fast does the temp go up...
why other than the gauge do you think its overheating... is it bubbling and spewing out water or what?
when you lift the hood... can you smell anything abnormal?
does it feel hot.. when you lift the hood does alot of hot air ram at you?
and you still got the waterfall? drive your car to the nearest steep hill so the radiator is at the highest point... make sure the engine is still cool... turn off... take off radiator cap... start the car... keep topping up the radiator while it's running (with the heater on full blat) and keep doing this till you don't see any bubbles come out... put the cap on and see how she goes

what colour is the oil on your oil cap?
pull out your dipstick... is it normal coloured oil?

lemme know how you get on :)

Thankyou for the reply. At this stage I can only answer a couple of those.
The car has just had an oil change in the shop. The shop were to do a full service but could not get all the parts so asked me to take her away for the weekend and bring her back next week to finish off. Before that the oil was normal and no milkyness.
The heater worked fine and blew hot air.

I noted the overheating in traffic when stood still. Once it started getting hot it was very quick.
At the time I was at an intersection crossing the bottom of a big hill and the traffic was stopped with me right across the downhill. Suicide city.
Once I could stop safely I lifted the hood and could hear steam hissing through in the radiator cap. There was steam in the expansion bottle. The engine did not smell hot but then again it is not caked in old oil and grime.

I have now had another HG tast done and the shop reports all fine. I have had the water pump removed and checked and this is also fine.

I am hoping that the problem was an air lock that blew the coolant out. Why it never came up on the shop test drive I dont know.

Oh well, what a Supra life he he

hi
the worst time for gulping air must be when fitting a stat.Jap motors in general need burped when the stat opens throwing out a bit of water but allowing full water throught system-perfect.A resevoir working on a thermo syphon system cant do much else +aint ideal.
Drilling a hole in the stat may work fine but without a jiggle or complete blocking of thermostat youve surely adversely affected the specific aperating range to one of guesswork.the stat being fitted to obtain maximum engine operating efficiency quickly,encludes a restriction in my mind vital to allow coolant to slow down enough to absorb heat to allow system to work right. Lots of garage probs exist cos the stat didnt open right first time before it was burped ,or
it had an underlying prob not so easy noticed without spending extra time that customers are loath to pay for possibly nothing cos time is money!
With enough information from you im sure folk here can eliminate likely faults ,id try motor again if garage says ok but dont trust the gauge if air may be an issue cos you wont know if it boils. :blink:

hi and thanks for that,

I have had the car back now 24hrs and seems fine but I do have the hole in the thermostat. I am keeping a close eye on things and going a few short distance runs in both open road and heavy traffic before I do anything adventurous.

I trust that on this occassion I was lucky and got away with it.

I am intrigued to hear two sides of the story about thermostats. That should be a bigger issue in the same way that HG bolts have been debated.

well it spose it would be an interesting debate... i was told that trick by a radiator company

their reasoning:

occasionally the little toggle thats in the top of them gets stuck so they drill the hole to counter it in case it happens...
i myself haven't done this as i haven't needed to...
but if you don't feel you want that in yours.. thermostats being as cheap as they are you can always buy one hehe

good luck on the car and my best hopes your overheating problems are gone ;)

Hello again.
After all that I had the waterfall again and this time I just had to trust my instinct. So, after one weekend, three evenings of cleaning and reassembly I have a new CHG.

For anyone who is interested DONT be put off by thinking this is a hard job. Get the manual and photocopy it all out into the right order as many manuals flip backwards and forwards to other chapters, get all your tools out, put the car on ramps, depressurise the fuel system, disconnect the battery, use lots of labels to attach to things and get on with it.

The only thing I had a problem with was not having six fingers on each hand that were about 10inches long and with universal articulating joints. That would have made the whole job a lot easier as EVERYTHING is just so hard to get to. In the end I bought a pair of locking artery forceps and thay gave me the extra reach and grip. I bought those from a sporting store as they sell them for fishermen to get hooks out of toothy fish.

The timing belt was a doddle and you dont even need to take the lower cover off. Just clamp the belt carefully against some packers before you release the tension and then lift if off the sprockets. Usual cautions apply.

The turbo was a pain to get off because of the oil feed pipe location. In the end you have to make up some really long extension sockets and get it from underneath but it can be done.

I decided not to have the head/block or manifolds skimmed because all were straight and flat when checked with a feeler and straight edge. The only time you need any help is to lift/drop the head. To make that easier I raised up a platform around the car with pallets so we were could be more comfortable when handling the head as it was quite high on ramps.

So far the car is behaving impeccably and I will give you an update if there is one.

Okay, I've ran out of options. I read your message on overheating and can't seem to pin point the problem. Things I've done so far:

1) Brand new radiator.
2) Removed the thermostat
3) New fan clutch
4) Added K&H Bloc Seal - Hoping it would help if I had a BHG.
5) New radiator cap

I did remove the fan shroud because it was damaged but I doubt if it would overheat because of that. I've ran it for an hour and a half in the drive way. Take it for a ten minute trip on the freeway doing speeds up to 90 with no problem. Head back up the hill which is about a mile and half with about a 40 degree incline and it OVERHEATS. The temp gauge goes immediately to red and the radiator begins to bubble. No bubbling in the reservoir.

I read that I could a have air lock and should burp the system. I've set it on an incline ran it for an hour with the heater on so I'm assuming that's enough though I'm still getting small bubbles when I take of the radiator cap. Also, what is the viscous fan. Just a weekend mechanic who loves his supra (87 non turbo) so please make your answers for a "mechanic dummy". Thanks for a great forum.

Hi, sounds like the dreaded cylinder head gasket. Sorry.

I did mine as reported almost 6 months ago and all is well. Dont be afraid to have a go yourself.
If you need convincing get a sniff or block test done at your local garage. That is a chemical added to the coolant. If it turns (green I think) then you have exhaust gas in the coolant.

I would not mind a bet that when you do get the head off the leak is between 5 and 6. thats always the one to look for.

Best regards

Chris

unforuntately i agree with the above... bhg :(

get a block check or leak down test done, this will tell you if you have a bhg

viscous = clutch fan :)

Thanks for the feedback. I guess I was hoping for something different. Getting a little too hot for me to be pulling the engine apart so I think I'm going to give one of these block seals a try again. I've heard several people say that these work pretty well. I know it's not the best approach but if it doesn't work I'll be forced to change the gasket anyway.

Has anyone used any of the block seals? If so, any recommendations. I realize it can do damage to the engine but at the price and time it will cost me to fix it. In my case, it may be worth it.

I've used prestone sealer plenty of times, works nicely, and may i suggest for a bhg , you use the prestone sealer for big leaks.

Should I remove the thermostat when adding the block seal? Just put it back in last night thinking my problems was solved. :angry: Also, the directions says not to run the car at high speeds (freeway) with sealant in it while I've heard others say to run it in order to seal all the leaks. It seems to make much more sense to run it for a while to have the sealant run through the whole system.

Thanks again for your response

Well, I've given up on the quick fixes and decided to go ahead and change the head gasket. Figured I'd just buy the gasket set (head, manifolds, etc) and change all of them and the timing belt while it's apart.

While I have everything taken apart, any recommendations on things I could do to either prevent additional problems later or add a little extra performance ;) . Not looking to street race but do enjoy openinging it up once in a while. This is a non turbo 86.5. Also, I've heard several people mention steel gaskets. Any particular brand and where to purchase them would be great.

you need to have the head checked to see if it's warped .also check the block for smoothness
you shouldn't just replace the gasket .
going with a metal hg is not cheap and is really for someone who wants to go mental with boost
a stock gasket doesn't need the surface as smooth as a metal gasket . the stock gasket material is more forgiving of the block and head surface
condition
http://www.ddmcse.com/turbo/bhg_2003.htm

here is a shot of a metal headgasket
http://www.ddmcse.com/turbo/images/mhg.JPG

tearing apart the head is really not as hard as you may think
just takes time, not really any special tools need a torque wrench

i used this guide when i did my 1st one ,, but i didn't go through the effort of preparing the block which is why I got to do it again.
http://www.geocities.com/MotorCity/Speedwa...y/1636/bhg.html

Sealant No Workie
 

Why, you ask, won't radiator sealer work on the 7M BHG problem.??

Because the "usual" BHG starts out as a tiny hole from a combustion chamber (usually #6 cyl) to a water passage.

The enormous pressure during combustion pushes the gasses 'into' the cooling system. This then builds up too much pressure and causes coolant to eventually over flow into the recovery bottle.

The sealant only works when the coolant is trying to leak 'out of' the cooling system to atmosphere. It plugs the hole.

Gasses get into the heater core due to a BHG.

Air gets into the heater core when the coolant level is allowed to drop in it. I suppose you could pinch the 2 heater hoses before you open the system, to prevent the coolant from coming out.

But I don't recommend this with old hoses, as it may cause them to leak later.

Also, the dangly thing on the thermostat can be snipped off before you put it into place. This will allow air to 'more easily' escape from the engine, and into the radiator, where it eventually will be pushed out into the coolant recovery bottle.

And....even opening up that hole by drilling it to 1/4" will NOT effect the operation of the thermostat, as it will still open and close normally, to allow the flow of coolant.

When your system is up to temp, the thermostat is wide open anyway.

Remember, the 7m motor (with a standard pump) does not flow much coolant at idle. AND...the fan does not draw much air at idle. I read many threads where the fellow says it gets hot at the stop light. Thats why I use an electric fan here in the desert.

I am mostly driving in town, with the A/C on, so I want lots of air thru the radiator at all those stops.

OVERHEATING!!!!!! STOP thing head gasket!
 

If you have problems like this or any other heating problems check ur car, if you have 100k+ miles and you replaced the thermastat... and it still over heats go to a parts store and just buy a new fan-clutch! many people think the fan is just the fan, IT'S NOT! the round metal part that the fan it self bolts to is the fan clutch. to test if it is your fan clutch, simply turn the fan by hand, if you can turn it with eas, replace the fan clutch, i garanty that it will fix your heating. a good fan clutch will have a strong resistance to being turned. it should not be easy to turn. P.S... it will fix your overheating, even with a blown head! i buy supras for cheap from people who think the head is blown. then just replace the fan clutch. trust me it works!

What kind of guarantee?? $$$ ?

All the 'cooling' in the world did not 'repair' my BHG.

Oh dear. Everything i've read here i've done. Block test, thermostat, burping, flush, blah blah blah.. On block test there is no exhaust gases in my cooling system, the car was purging through the overflow and yes, i too got extremely scared about a BHG.. Although i guess its not the problem. I had a coolant leak through my thermostat res,.. fixed that, no more overflow. BUT!!! it still overheats randomly, weirder part.. if i put it in neutral while driving and its overheating, the temp gauge imediately drops to normal operating temp, and stays there.. answer that riddle

Had a similar problem, when throttling it would overheat but as soon as i backed off/decelerated it would cool down again, I was leaking between combustion chambers. Have you done a compression check?

Yea, the numbers were all over the place. From the 6th cylinder to the 1st everything was weird. 1st was 120 2nd.. i can't remember.. 3rd.. i can't remember, 3rd 145, 4th 155 6th 160. How would one go about fixing this issue if it was a leak between combustion chambers?? Because thats kind of how it is... Except, if i turn the car off, then start it again, its at normal temp.

If it's that ALL OVER the place then yes head gasket has fubar'd.

It's not overly common to blow between cylinders, usually you get the water mixing with oil variety.

What work has been done on it? Is it stock or got mhg or what?

Its completely stock. Nothing at all done to it. Its weird because the car runs like a top. Just randomly overheats. Definitely not a all the time deal. Once in a while. And it stopped spewing when i changed the thermostat housing bolts from the leak i acquired from the bolt i broke

To verify, I would get the engine warm and do another compression check. Let us know the numbers (so write them down hehe) and we'll go from there. We don't want you pulling off a head unecessarily ;)

ALSO!! I found an exhaust leak.. coming from one of the gaskets between the exhaust manifold and the downpipe.. Could that cause this problem?? The mechanic who did my compression test said it was fine.. I just remember the numbers being weird. It was only cranked for 2 seconds on each cylinder. I didn't think that would give u an accurate reading. And the block test came out clean. All i know is that this problem is very annoying and i can't wait to either fix this issue of get rid of the car.

Yea.. good god that wouldn't be cool. And yes, of course the engine was cold. Its very difficult to work on top of that engine when its hot... Heat burns.. But i'll give it a shot.:eek3:

I wish i had this thread a while ago!!
 

i have an 88 stock supra 5-spd (non-turbo) and recently found out that the gaskets/torque settings have to be changed from factory standard. Several years ago the car starts randomly overheating. At first it was slightly hotter than normal, nothing suspicious in the oil or exhaust (that i remember) then one day it starts to boil into the red, the gasket went and i sent out a smoke screen for half a mile. I bought steel reinforced gaskets and i believe the new torque settings are 72lbs (Original was 59lbs i think). Im back on the road and watching things closely.

supra is a great car but i wish i found out earlier what problems it had so i could anticipate them before they happened. im learning on the go.

Well I've got some overheating on my 87 NA supra. The engine seems to run fine but then a lot of steam starts coming out of the exhaust and the needle starts to go to the red. Thermostat has been replaced and all hoses have been checked. What else should I look for before taking the head off?

other possibilities who knows/radiator cap?
 

i have recently found out that my supra is very outside air temperature sensitive, for some reason it leaks a little rad fluid in the exhaust(about a half quart every 100 miles) when the air temp falls below 35 degrees. so i have to keep tabs on the coolant level. also you might want to check your resevoir, to see if it fluctuates, if its always the same or just going out and not going in then there is a system leak somewhere. not sure what else to look at besides the head gasket. hoses/water pump/ thermostat/ gaskets/ also i believe radiator cap pressure should be 13psi.

Hmmm, well it seems that coolant is only being pushed out of the reservoir tank and not drawn in. How could I identify a leak in the system? Would that be a big enough problem to have steam out of the exhaust?

almost 99% sure thats a headgasket leak
 

im not an expert but im almost sure you have a head gasket leak because thats the only way it would get into the exhaust that i know of. so basically if it hasn't been replaced its going to need to be replaced. also in the mean time you have to check your rad fluid level every time it is cool berfore you drive and make sure when you look in to the radiator you can see some some fluid(don't fill to the complete top of cap) you can no longer trust your reservoir and must baby/nurse your car until you replace the gasket.

when you see your needle bouncing it means your down to your last quart of fluid and need to pull over. Get a pressure release cap so you can bleed the pressure off instead of waiting 45 minutes for it to cool........ugh im having flashbacks, i need a drink.

Alright, well thanks for the tips. I think I'm gonna dive in and do this head gasket job this weekend, any tips on doing it? Are there steps or guidelines I should go by?

also antifreeze brand may help/other posts
 

i havent done a scientific study but i feel that PEAK Global antifreeze for import cars seems to work alot better than prestone just an observation. also here are some posts on the topic that might help.

http://www.toyota-supra.info/forums/...ir-w-pics.html

http://www.toyota-supra.info/forums/...et-repair.html

http://www.toyota-supra.info/forums/...-symptoms.html