Coolant issue

black ice mike

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Ok guys, I've had my supra for about a year now and there's always been a coolant issue. At one point you could drive it for a little bit and be fine, but then it'd start pushing coolant out, so after a while the water pump went, and now it's doing something I've never seen. I got a new gauge sensor because the one day I saw the gauge rapidly fluttering up and down. So, last Friday I went on a drive with my cousin , wasn't driving it too hard but when we came to a stop the temperature rose, until I started driving again. Then it went back down, so he suggested that there could be a clog somewhere in the hoses. Now today I was driving around and granted it's around 95 outside, it was 75 on Friday, but now it does the opposite of what it did on Friday. It got hot when I drove it and stayed at a steady temperature when stopped. I'm very stumped as to what it could be. I don't think it's the HG because I pulled the valve covers off and checked the torque of the head bolts which were torqued to 74 ft lbs. I'm going to put in a 3 core radiator when I get the money, but if anyone has any suggestions on what it could be that'd be great.
 

Roger UK

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The stock radiator is fine, so don't bother changing that ! (unless you're doing a 400hp modification)

I'm afraid if you have water gushing out into the overflow bottle, that usually indicates pressurisation in the cooling system, due to a blown head gasket. As you're probably aware, the 7M engine is VERY prone to it . . . and just because you have re-torqued your head bolts doesn't mean it hasn't blown.

Why did you change your Water Pump? When you took the old one off, had the blades all corroded away? (this often happens in the USA, as owners will have thought it's OK to just use water, but Antifreeze also has Corrosion Inhibitors, which are essential)

If that was the case, your engine WILL have seriously overheated at some point . . . and unlike most engines, just ONE bit of overheating on one occasion on the 7M almost ALWAYS causes the Head Gasket to fail.

The thing to bear in mind is that once the head gasket is damaged, it won't ALWAYS leak . . . sometimes it will be fine . . . but then another day it will start leaking and pressurising the system. But it will keep getting worse and worse. And if it leaks across to the Oilways and you get ONE bit of Coolant in the oil, you can kiss goodbye to your Big End bearings too! (another weak point on the 7M engine)
 

black ice mike

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I changed the water pump because it died on me the one day. The belt came off and wouldn't stay on because it wobbled. The engine has 259,000 miles on it but the previous owner kept it in fairly good condition, so I don't know if it was ever done. I would think so because the head bolts were torqued properly
 

suprajim54

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Just do the block test. I tested mine about 6 months ago and failed. Tried to retorque the ARP Head Bolts, but still failed the block test afterward. However, I've put a thousand miles on it since then and beat on it every once in awhile. I have no smoke and don't feel like power has decreased. No mixing of coolant in the oil, but do occasionally see what I think is oil in the coolant.I know it will eventually go, so I have another engine on the stand that I'll have ready by the time this one finally goes. If I drive like a normal person and take mostly short trips, I could go a week without seeing the birdcage light. If I try to go any further than about 75 miles in a single run at highway speeds, I'll have to top up the overflow and possibly the radiator before I go anywhere else. Good luck with the diagnosis!
 

hvyman

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Head gasket is likely blown.

Also the fan clutch is most likely bad as well.
 

Roger UK

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If the plan is to replace the complete engine, then you can keep on driving and just top it up when it overflows - eventually it will be undrivable.

However . . . as I mentioned, once coolant starts getting in the oil it will permanently damage the big ends - even if they don't fail straight away, they will in the future.

So if you want to keep this engine, you need to stop driving it and replace the Head Gasket.

If you doubt what we're telling you, get a garage to do a sniffer test. (or get a kit and do it yourself). Basically, it detects if there are any exhaust gasses getting in the coolant. If there are, then the HG is obviously blown.

Normally you don't need to bother doing this, as if you run the engine from cold with the rad cap off, once it has warmed up you will see tiny bubbles coming out the top of the radiator. That proves you have a BHG.
 

black ice mike

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Been kinda busy with a new job, and actually forgot about this XD, I don't plan on keeping the engine but its just something that's always been a pain, that has prevented me from going in any trips with it.