Marmoot Posted April 15, 2009 Share Posted April 15, 2009 Hiya, greetings from downunder I am just hoping our collective deduction power can help me with my Supra. FYI it is an NA-TT swap, non-vvti. Recently I had a blown headgasket and overheating fixed. Items changed include: - skimmed head, new head gasket - new radiator, tripple core upgrade from the standard (standard NA that is) - new thermostat - new water pump, OEM supra, with OEM viscous fan and OEM fan shroud - new rad cap - leaky hoses changed, no more leak - coolant system pressure tested OK - new standard sparkplug My A/C and heater functions just perfect. When under normal operation, including stuck in traffic jam etc, the temperature needle would stay where it is. Eg., if it is at halfway then it would stay halfway, and if it is high then it would stay high. As soon as I get the car under wide throttle, and especially on boost pressure (above 0), then the temperature gauge would move up. The wider the throttle = the faster it would move up. If I then go gently again, the temperature gauge would just stop moving up and stay where it is regardless of traffic. Only when getting on to highways and moving at 100kph then the needle would very slowly creep down to halfway. Running on A/C would increase the rate by which temp needle would go up. Also, the coolant does not boil, even with the temp needle near red (yes, I was stupid enough to actually test this). I am running 50:50 water-antifreeze I'm stuck. Can't think of what may have caused this (see the list of new parts). I would try getting something to replicate the bottom engine tray (which is currently absent) sometime next week or the week after, but I doubt that this is the culprit of my problem. I don't think it is cooling problem since the car can hold its temperature in traffic jam and 100kph air flow does bring the temperature down. I am thinking it may have something to do with the turbos? It is a stock sequential twin turbo setup running stock boost btw. Help.... Quote Link to comment Share on other sites More sharing options...
Scott Posted April 15, 2009 Share Posted April 15, 2009 Help.... My first guess would be an air lock. I recently had the same trouble with my 106 and i have read of people having similar issues with the supra. The problem is that the expansion tank and radiator aren't at the highest point of the engine. Park the car facing up a hill, get the car up to normal operating temperature so that the thermostat is open (what my mechanic didn't do) and very carefully open your radiator cap. Hopefully you should be able to top up the radiator. My 106 took 2 litres extra once the thermostat was open. A little trick is also to fill the pipes leading to the heater matrix at the back of the engine. This is a common place for the air locks to happen. Don't do this with the car running or when hot though, do that cold. Keep things simple to start off with. My next port of call would be to remove the thermostat completely and see what happens with the temps. Who did the work? Quote Link to comment Share on other sites More sharing options...
Marmoot Posted April 15, 2009 Author Share Posted April 15, 2009 Sorry to ask, but I'm interested in your logic on how airlock gets connected to only heating up under load. Care to explain? The work was done by a garage in my area. They're generally very good and meticulous. But yes I agree they are human so I would be open to any suggestion on possible workmanship defect. Would be costly to ask them to reopen the engine up though, so I'd prefer to keep this as ultimate last resort. Quote Link to comment Share on other sites More sharing options...
Scott Posted April 15, 2009 Share Posted April 15, 2009 Sorry to ask, but I'm interested in your logic on how airlock gets connected to only heating up under load. Care to explain? The work was done by a garage in my area. They're generally very good and meticulous. But yes I agree they are human so I would be open to any suggestion on possible workmanship defect. Would be costly to ask them to reopen the engine up though, so I'd prefer to keep this as ultimate last resort. I usually find that idling is the worst for the temp overheating but it depends where the airlock is. Different cars react differently to airlocks. It usually depends where the temp sensor is and where the theromostat is in relation to the lock. Its the first thing i would try anyway. Quote Link to comment Share on other sites More sharing options...
Terminator Posted April 15, 2009 Share Posted April 15, 2009 Recently I had a blown headgasket and overheating fixed. Help.... If it is still over heating, it sounds like they did not fix it. Take it back. Don't under estimate the value of an undertray, Toyota put them there for a reason. In a totally different track car, we had very high water temps without a tray then added a simple flat sheet tray and temps came down and stayed normal. Air always takes the path of least resistance. On the same car we added a simple bleed valve on the top cabin heater hose, to make getting rid of airlocks easy. Quote Link to comment Share on other sites More sharing options...
Marmoot Posted April 18, 2009 Author Share Posted April 18, 2009 You are right. I now believe the only possible cause is combustion gas still blowing into coolant line. A.k.a. there is still a leak. Block has been confirmed perfectly fine. Cooling system is confirmed to be free of blockage and leaks, and has new water pump, thermostat, rad cap, radiator, and some hoses, and all are confirmed to be in working order. I did what you recommended, parked the car uphill and watch the radiator. Small bubbles occassionally came out, so it IS a leak. Right now I have discussed with the mechanics and they will try retorqueing the head as a first measure. If it solved the problem then it makes sense. Perhaps the gasket compressed ever slightly during the first few heating sessions and retorqueing might solve the situation. Or perhaps the studs just expanded, etc. If that do not solve it, the mechanics mentioned a possible crack or porous head which may need new head. Sigh. I hope it doesn't go up to this. Otherwise I'd have to shell out quite a bit of $$$ for new head. Any other ideas worthy of investigating? Quote Link to comment Share on other sites More sharing options...
mikeyb10supra Posted April 18, 2009 Share Posted April 18, 2009 Few questions....firstly, if there are bubbles coming up then there is air in there and secondly...was it an OEM (ie toyota) replacement radiator? Quote Link to comment Share on other sites More sharing options...
Scott Posted April 18, 2009 Share Posted April 18, 2009 If the mechanics were worth their salt to begin with they should have checked the head. It sounds like a bunch of cowboys working on your car buddy. When you change the headgasket its always best to get it skimmed to make sure it gets a perfect seal. The bubbling from your coolant MAY have been an air lock but there is no way after checking all the stuff you have that its JUST that. How is your overflow tank looking? If its a HG failure it would pretty much spew out coolant when up to temp with the thermostat open. The gasses would push the coolant out through the rad cap and out through the overflow. Run it up to temp and have a look at it, very very carefully open up the rad cap. If it spews coolant out it sounds like the HG to me. One VERY important thing when topping up the coolant is to make sure the thermostat is open while gently topping up. If you just fill the rad etc then you will end up with a massive airlock as the thermostat isn't opened. When it does open the air inside will start to expand and cause the symptoms you describe as well as the above symptoms. I'm pretty sure this is not the case but it is definitely worth a try. Run the car up to temp till the thermostat opens, when it does carefully open the radiator (damp towel). If it is an airlock and it hasn't been filled right there should be plenty of space in the radiator to fill in lots more coolant. Do this on a hill. Quote Link to comment Share on other sites More sharing options...
Marmoot Posted April 18, 2009 Author Share Posted April 18, 2009 The mechanics have been great all these years and they work on my other cars, including my previous N/A Supra before. So I more or less trust them. However, they are human so we have to acknowledge that sometimes they may get it wrong. Coolant system and combustion chambers were pressure tested and the results were satisfactory. My suspicion is slight leak in the head gasket that allows the engine to function properly on low condition (e.g., idling or very low throttle) as exhibited by it holding the temperature well even in traffic jam, but high pressure (e.g., boost, wide throttle, going uphill) may cause combustion gas to blow through. Does this make sense? The bubbling only happens when I open the throttle a bit wide. Also, there seems to be a few dots of oil (black, roughly as big as this dot --> . ) floating up with the bubbles every now and then. That's why I suspect non-ideal torqueing on the head studs is a possibility. Coolant in the reservoir did not boil, while before the head repair the coolant would boil even when the temp gauge is still halfway. The head was skimmed/machined during the repair by reconditioning specialist. Is it possible for porous head to be hard to detect? P.S. The radiator is now a new 3core 2" aluminium aftermarket replacement. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted April 18, 2009 Share Posted April 18, 2009 Have the mechanics not heard of a sniffer test to see if there is any combustion gasses in the water system, there are electronic and chemical testers, one of the first things they should have done, given your problems. Quote Link to comment Share on other sites More sharing options...
Marmoot Posted April 18, 2009 Author Share Posted April 18, 2009 It was indeed done. No anomalies detected. Perhaps they were doing it on idle, or the equipment wasn't good. Quote Link to comment Share on other sites More sharing options...
Scott Posted April 18, 2009 Share Posted April 18, 2009 It was indeed done. No anomalies detected. Perhaps they were doing it on idle, or the equipment wasn't good. Yeah, they really know what they are doing Buddy, if a sniffer test and chemical analysis has been done on the coolant then its a big fooker of an airlock. Do you do anything yourself? Just asking as the tests i have mentioned are very very easy and could be done in half an hour. Quote Link to comment Share on other sites More sharing options...
Marmoot Posted April 18, 2009 Author Share Posted April 18, 2009 I did what you suggested in your first post (park it uphill etc...). Airlock wouldn't have oil drops in the coolant, would it? Quote Link to comment Share on other sites More sharing options...
Scott Posted April 19, 2009 Share Posted April 19, 2009 I did what you suggested in your first post (park it uphill etc...). Airlock wouldn't have oil drops in the coolant, would it? No reason for that to happen with an airlock. An airlock is just that, air in the system that can't get out. When it gets hot, it expands. This causes the coolant to be pushed out. Its a lot more complicated than you would think to flush out the system properly. A lot of people when flushing the system fill it from the heater matrix pipes. This can help quite a bit. One thing to seriously try is.... remove the thermostat then fill the system while the engine is ticking over. I'm not saying its definitely an airlock. Its just the best idea to completely rule out 1 thing before going onto another. What you say 1 min says headgasket, the next it says its not. Your findings are inaccurate so far. Lets get them definite. Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted April 20, 2009 Share Posted April 20, 2009 One thing i think scottm has missed, when topping up the coolant and checking for airlocks, make sure your heater is on hot, this opens the matrix and allows water to flow through it. If it was set to cold when it was originally topped up then it'll be empty meaning it could well be full of air. Quote Link to comment Share on other sites More sharing options...
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