Supra Forums banner

1 - 18 of 18 Posts

·
Registered
Joined
·
143 Posts
Discussion Starter #1 (Edited)
I searched around but could not find exactly the information i am looking for. On my overflow bottle i marked off my hot and cold temperature marks. It has been pretty consistent when hot it is at the hot mark and when cold at the cold mark. however i have noticed twice now i will be driving down the road and all of a sudden i loose heat in the car, even with the temperature all the way up. after parking the car and letting it cool down, the overflow level is way above the hot mark. but then i will drive around for the next couple of weeks with no issues and the level goes back to the proper levels. Then again the other night i lost heat in the car and sure enough the overflow is really high. Anyone have any ideas what could be happening.
 
Z

·
Guest
Joined
·
0 Posts
I was having this problem when my car was still running right before the deliciously infuriating BHG. Exhaust gasses would find their way into the cooling system and blow the coolant out into the overflow tank, eventually blowing the rad cap right off.
 

·
Registered
Joined
·
5,966 Posts
Your heater control valve sitting next to the charcoal cannister in the engine compartment may have a bad solenoid.

It is a small part, but very costly, (160.00) cheapest with discount.

I picked one out of the junkyard ( any year 7m will work) for $3.00 only.

Also, while I was at the junkyard, I looked around other Toyotas which may have utilised this solenoid and i found the Cressida, the 1986-88 Camry and the Celicas had this valve. All you need to do is splice the connector from your supra onto the other model's solenoid.

A quick fix is , unplug the vacuumn that goes from to the solenoid, and plug it directly to the round diaphram cannister.

G/luck
 

·
Registered
Joined
·
143 Posts
Discussion Starter #5
thanks for the information. Is that common to happen when that valve gets stuck having coolant levels go up? again this has happened mabey 2 times in the last month and i have been checking my overflow relegiously everyday without any issues except for when my heat stops blowing.
 

·
Registered
Joined
·
2,649 Posts
No, this is not common. If your heater valve gets stuck in the OFF position, you will usually just lose heat in the passenger compartment. Your overflow bottle changing levels like you mention is unlikely to be affected by this valve.

Sounds like you need to visit a shop and get a block test. This will check for exhaust gasses in your coolant. Usually used to find cracked blocks, but in this case we are looking for a blown head gasket. The test is quick and cheap - likely $30 or thereabouts.

If the test is positive, you likely have a minor head gasket failure. Minor is a good thing, as it means you can fix it, hopefully before it causes any real damage.
 

·
Registered
Joined
·
143 Posts
Discussion Starter #7
i just had the gasket changed last year. I would be suprised if it went so soon after. I have mabey put 9000 km on the car since then. And wouldn't a minor head gasket failure be more consistent. what i mean about this is that it happened twice in a couple months and the rest of the time the coolant level is where it needs to be. also why does it only happen when the heater stops blowing hot air. I will get a block test done. Do you think if it passes or is very minor that i would be safe to have the head retorqued down to 70 ft\lbs compared to the factory specs i have right now?
 

·
Registered
Joined
·
2,649 Posts
When you had the head gasket redone last year, was it only torqued to factory specs? Factory specs are seriously under what is needed, I would expect a HG to blow under that amount of torque.

Actually, it's the minor failures that are the hardest to spot. When the HG is only failing sometimes, it will often depend on seemingly unrelated conditions - like the outside air temp, how hard you are running the motor, all kinds of things.

If you load the engine hard, it'll blow exhaust gasses out into the cooling system, and displace coolant. Exhast gasses don't work very well in your heater - therefore, no heat. Unfortunately, they don't work very well in your cooling jacket in the motor, either, thus you will quickly get a warped head. They also contaminate your coolant, destroying it's anti-corrosive qualities, so your coolant will quickly start to corrode your motor, and so on, and so forth. I'm sure we're all too familiar with the bad effects of BHGs.

I would suggest, and I'd hazard a guess that most here would agree, that a head gasket job should always be accompanied with a set of ARP bolts or studs (they are only $100 CDN for the bolts) and torque it down to 75 foot pounds.

If it passes, you are likely safe to retorque them. If it doesn't pass, you're toast, need to do it again.
 

·
Registered
Joined
·
143 Posts
Discussion Starter #9
hey thanks for the info, i will get the test done and if all is good retorque them. If bad i guess i will be dishing out the cash to have it done again.
 

·
Registered
Joined
·
2,649 Posts
Good lord - you pay someone else to change your headgasket? That's an awful lot of labour to be paying someone else to do! Besides, when you do it yourself, you know it's done RIGHT.
 

·
Registered
Joined
·
143 Posts
Discussion Starter #11
yeah i wish i had the time to do it myself or could afford the downtime of not being able to commute from work and back. The shop i was refered to this time is very expierenced in dealing with blown head gaskets on the supra.
 

·
Registered
Joined
·
74 Posts
there's a free online service manual avail. Standerd hand tools is all you need, little common sense, and if you plan it right have the head resurfaced and get it back same day. That's 1500 bucks or more going towards repair not respect.
 

·
Registered
Joined
·
143 Posts
Discussion Starter #13 (Edited)
Just wanted to get a little bit more information and update everyone on my situation. i had the test done for a BHG and came back negative so there is no signs of any exhaust in my coolant. also had a pressure test done and i holding pressure fine. So what i am wondering is what else could be failing in my cooling system that would cause the coolant to overflow to much in the bottle but not experience any issues with temperature flunctuation or any other signs of cooling system issues.
 

·
Registered
Joined
·
2,649 Posts
When you lose heat, and leave the heat on auto with the temp set high on the climate control, does the fan turn on and blow cold air, or does it not blow at all?
 

·
Registered
Joined
·
143 Posts
Discussion Starter #15 (Edited)
the fan actually blows cold air and no hot. actually one night i was driving and all of a sudden it started blowing cold air, then i turned off the car and then turned it back on and started blowing hot air again. Also i have noticed when i come to a stop the air blowing will get a little cooler but when i start driving again it gets hot. I never really use the automatic climat setting. i always have it set to blow at medium and then i choose my temp and where i want it blowing (usually out of the dash areas.
 

·
Registered
Joined
·
78 Posts
I had exactly the same symptoms. Intermittent heating and floating coolant level, usually minor with regular driving but all the way to the top of the overflow bottle after hard boosting. Exhaust test done a number of times turned out negative. It ended up being a small leak in the gasket on #6 cylinder...
 

·
Registered
Joined
·
2,649 Posts
The auto setting has an advantage... it won't blow unless there is hot coolant in the heater system. Which allows you to rule out the heater control valve on the firewall as the reason for getting no heat.

Back to the basics, I guess - burp the cooling system. Park on a steep hill, wait until the car is cold, take off the radiator cap, fill up the rad if needed, fire up the car and let it run. If there is air in the system, it should work it's way up to the radiator and out. Keep refilling the radiator.

If that doesn't fix it, get your cooling system flushed completely.

If that doesn't fix it, consider getting the cooling system examined for blockages and leaks.

If none of these help... well, personally, I'd just run it hard and put it away wet until it fails, then buy a new motor.
 

·
Registered
Joined
·
284 Posts
I've had this problem before as well. In my case it turned out to be the same problem that Mikes7MGTE had. I had a very very small cylinder to coolant leak at the HG on #6. There's no coolant in the exhaust, and it's too small to be picked up by a compression or pressure test. So you get a slow accumulation of air in the system. Air gets trapped in the system easily, especially at the hear core supply line because it's the highest point in the system (hose is higher than the radiator cap... at least on my car). As temperature increases the trapped air will expand, making the loss of coolant worse. The path of least resistance for the coolant is through the engine and radiator to help protect the engine when coolant levels are low, so if there is a lot of air in the system you will not get any flow (or low flow) to the heater core. If this is the case then the contraction of the trapped air and coolant should be enough to suck the recovery bottle dry when it cools down after being at full temperature and pressure.
Here's how to get things working.
Starting from cold system conditions, release the radiator cap pressure and allow the car to warm up to normal temperature (open thermostat) using idle only. If the heater is not working and the heater valve is OK, you coolant level should be way-low. Slowly fill the radiator allowing time to work the air out a bit. Forcing the upper heater hose down with you hand helps a little as well. The suggestion to park on a hill works the best though (puts the radiator cap at highest point). At this point the heat should start working again. Replace the radiator cap and fill the recovery bottle. Over the next few days any remnants of air should get worked out naturally and coolant level should stabilize.
If the fluctuation continues then you probably have a small leak somewhere.
If the heater control valve isn't broken and you get no heat due to low coolant levels, be sure to fill the radiator (don't just check the recovery bottle, pull the cap and check). If the coolant level is low enough that the heater quits working, then you're running dangerously close to not having enough cooling capcity to keep the engine at normal operating temperatures (I learned that one the hard way). I hope this helps folks.
 
1 - 18 of 18 Posts
Top