Coolant smell under boost
10-26-2016, 10:46 PM
#1
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Coolant smell under boost
I'm having a problem that I'm having trouble figuring out. Looking for some suggestions on what to try next.
Car: 99 Miata with t25 oil cooled only.
Aftermarket mishimoto radiator. Otherwise stock cooling system. Unopened stock engine with 145k miles. Boosted for about 5k. No issues prior to turbo install.
Symptom: coolant smell under high rpm/boost. Zero smell during normal driving around. Only smells when I get on it hard
So far I have replaced my drain plug which was partially stripped thinking it may be blowing out under the car. It no longer leaks. Smell remains when accelerating hard.
I removed my heater core from the cooling system loop to make sure it's not leaking in the cabin under pressure. Smell remains
I rented a pressure tester and tested my cooling system (while the car was cold) up to 20psi (rad cap is for 19psi) and saw zero drips/leaks/weeping coolant at all. Left it at pressure for about 5 mins and pressure didn't drop any noticeable amount. I restarted the car to see if my cylinders had coolant in them after the test but didn't smell anything.
I pressure checked my rad cap and it seemed kinda flaky not testing consistently so i replaced it with new oem cap and went for a test drive. Smell remains when I accelerate hard.
Not sure what to check next? I have never done a leak down test on it but if my head gasket was leaking wouldn't I be pressurizing the cooling system, not sucking coolant into the cylinder? And if I was sucking coolant in wouldn't that have been present during my coolant pressure test by filling my cylinder with coolant/dropping in pressure/smell on startup from a pool of coolant in a cylinder?
Any suggestions would be much appreciated!
Car: 99 Miata with t25 oil cooled only.
Aftermarket mishimoto radiator. Otherwise stock cooling system. Unopened stock engine with 145k miles. Boosted for about 5k. No issues prior to turbo install.
Symptom: coolant smell under high rpm/boost. Zero smell during normal driving around. Only smells when I get on it hard
So far I have replaced my drain plug which was partially stripped thinking it may be blowing out under the car. It no longer leaks. Smell remains when accelerating hard.
I removed my heater core from the cooling system loop to make sure it's not leaking in the cabin under pressure. Smell remains
I rented a pressure tester and tested my cooling system (while the car was cold) up to 20psi (rad cap is for 19psi) and saw zero drips/leaks/weeping coolant at all. Left it at pressure for about 5 mins and pressure didn't drop any noticeable amount. I restarted the car to see if my cylinders had coolant in them after the test but didn't smell anything.
I pressure checked my rad cap and it seemed kinda flaky not testing consistently so i replaced it with new oem cap and went for a test drive. Smell remains when I accelerate hard.
Not sure what to check next? I have never done a leak down test on it but if my head gasket was leaking wouldn't I be pressurizing the cooling system, not sucking coolant into the cylinder? And if I was sucking coolant in wouldn't that have been present during my coolant pressure test by filling my cylinder with coolant/dropping in pressure/smell on startup from a pool of coolant in a cylinder?
Any suggestions would be much appreciated!
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10-27-2016, 12:27 PM
#4
Truthfully it could be any of the plugs on your block or head. Coolant pressure increases with RPM and heat, both are happening under hard driving - I'd inspect your cylinder head/block deck mating point for any signs of coolant or leaks. Sounds like it could be a head gasket that's sealing enough for normal driving but can't hang under higher load conditions and increased cylinder pressure.
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10-27-2016, 12:39 PM
#5
Are you having to top off coolant? Assuming you do have a leak it has to be tiny and probably dripping on something hot. Look around the radiator for evidence of a pinhole leak. It'd be warm enough to evaporate off the coolant pretty quick; makes more smell and hides the evidence of the leak unless you look close.
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10-27-2016, 01:29 PM
#6
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IME, turbo Miatas are very prone to doing this. My theory is that it's the turbo coolant lines, that they leak a little bit near the turbo when it gets hot, but since they drip onto the turbo itself it boils immediately and you never see coolant anywhere, you just smell it.
Keep an eye on the coolant level and if it's not dropping appreciably IMHO there's nothing to worry about.
--Ian
Keep an eye on the coolant level and if it's not dropping appreciably IMHO there's nothing to worry about.
--Ian
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10-27-2016, 01:43 PM
#7
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Thanks for the comments
i don't have water lines hooked up to my turbo so that can't be it. Though if they act anything like my drain block/fitting I could totally believe that was the culprit. I can't get that thing to fully seal.
Im not sure if I have to top it off or not yet since I kept having to drain and refill when I tried multiple times to get a good sealing solution for a leaky drain plug. I only drive about 10 miles per day so I'll have to wait a while or for my next long trip to check the fluid level loss rate.
Im planning to rent a pressure tester again and try to check better around the back and under the intake manifold. I only tested it cold before and pressurized it to 20psi. Is it safe to leave the tester on at zero pressure, warm up the car, then add pressure as needed with the tester while everything is running? What is a safe pressure limit to push the system to? Obviously I'm getting up there when I'm accelerating hard but it must be below about 19psi (cap is rated for 19) or I would be blowing a bunch of coolant into my overflow tank right?
i don't have water lines hooked up to my turbo so that can't be it. Though if they act anything like my drain block/fitting I could totally believe that was the culprit. I can't get that thing to fully seal.
Im not sure if I have to top it off or not yet since I kept having to drain and refill when I tried multiple times to get a good sealing solution for a leaky drain plug. I only drive about 10 miles per day so I'll have to wait a while or for my next long trip to check the fluid level loss rate.
Im planning to rent a pressure tester again and try to check better around the back and under the intake manifold. I only tested it cold before and pressurized it to 20psi. Is it safe to leave the tester on at zero pressure, warm up the car, then add pressure as needed with the tester while everything is running? What is a safe pressure limit to push the system to? Obviously I'm getting up there when I'm accelerating hard but it must be below about 19psi (cap is rated for 19) or I would be blowing a bunch of coolant into my overflow tank right?
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