[ansermet]

Howdy. Maybe someone else has experienced this. I have a 2001 9-3 2.0L. My coolant is disappearing. Often an inch per hour drive. Just had head gasket done by a SAAB master tech. Hoses checked and/or replaced. No milkshake oil. No visible oil in coolant. No findable drips. No sweet odor. No smoke from tail pipe. Coolant system pressure tested fine. BUT, on hard acceleration, with extended high boost, there is a terrible burning smell. Otherwise, the engine idles and runs perfectly. Thoughts?

 

[CarpeCyprinidae]

Check for cracks/leaks on coolant coolant lines..... and check for dampness on inner carpet. Why did you have the HG replaced before identifying the problem?

 

[jmkcc]

It's a sealed system so there has to be a leak somewhere. I'd try the pressure test again, maybe make sure to use a different testing tool. Can you tell if the burning smell is from the engine bay, interior cabin or tailpipe? How's the turbo bearings/seals? Not sure if it's possible for turbo to only leak coolant out the exhaust side under load, but sounds like this might be a bizarre little gremlin like that. I'd go so far as to wiggle the turbo shaft while doing a coolant pressure test if no other leaks are found first. Is the lower "elephant trunk" hvac drain in the engine bay clear? Any chance it's plugged and coolant from the heater core is dripping along the body/frame to an area you don't notice. Anything wet under the body especially by drain holes? Maybe interior leak is going directly under the carpet and sound barrier so the carpet's not wet. Any widespread moist areas in the engine bay - maybe pump leaking and the belt is disbursing a fine mist? Did the pressure test hold an absolute pressure with absolutely no decrease?

 

[jvanabra]

Sometimes after work spilled fluids will burn off of hot surfaces, so it's possible the burning smell is not connected to the coolant loss.

IME, a common source of coolant loss is the water pump, as it's buried down there and liquid leaks are hard to see if they aren't just being burned off.

Two things:

1. You can try UV dye in the coolant to help you spot an external leak. Kits are available cheaply from Amazon, and often you can rent the tools from Autozone etc. and just need to purchase the dye.

2. Just because a head gasket was done, doesn't mean it was done right. Even professional mechanics sometimes skip the should-be mandatory head check at a machine shop, and end up putting a marginal head back on the engine. Not saying your shop whiffed it, but don't assume because a professional did it that it was done professionally.

 

[ansermet]

Sometimes after work spilled fluids will burn off of hot surfaces, so it's possible the burning smell is not connected to the coolant loss.

IME, a common source of coolant loss is the water pump, as it's buried down there and liquid leaks are hard to see if they aren't just being burned off.

Two things:

1. You can try UV dye in the coolant to help you spot an external leak. Kits are available cheaply from Amazon, and often you can rent the tools from Autozone etc. and just need to purchase the dye.

2. Just because a head gasket was done, doesn't mean it was done right. Even professional mechanics sometimes skip the should-be mandatory head check at a machine shop, and end up putting a marginal head back on the engine. Not saying your shop whiffed it, but don't assume because a professional did it that it was done professionally.

Sometimes after work spilled fluids will burn off of hot surfaces, so it's possible the burning smell is not connected to the coolant loss.

IME, a common source of coolant loss is the water pump, as it's buried down there and liquid leaks are hard to see if they aren't just being burned off.

Tw things:

1. You can try UV dye in the coolant to help you spot an external leak. Kits are available cheaply from Amazon, and often you can rent the tools from Autozone etc. and just need to purchase the dye.

2. Just because a head gasket was done, doesn't mean it was done right. Even professional mechanics sometimes skip the should-be mandatory head check at a machine shop, and end up putting a marginal head back on the engine. Not saying your shop whiffed it, but don't assume because a professional did it that it was done professionally.

Hey, thanks for this tremendous response to the bane of my existence. I will immediately "action" these suggestions. I'll share a lot of them with my guy, except for the last part about maybe he didn't do the gasket job right!

 

[BobSaabit]

Look in the cylinders at the pistons. One or two being much cleaner than the others indicates a head gasket coolant leak into the cylinder.

Is the burning smell sweet or very foul? Sweet would be coolant; Foul is usually oil and it's usually dripping out of the pressure sensor on the rear of the engine onto the exhaust/cat.

 

[Flash635]

I recently saw someone using a vacuum to check the cooling system for leaks.
I thought it was odd but it makes sense; you can see a drop in negative pressure immediately if there's a leak and you're not forcing coolant into somewhere you don't want it to go.

 

[jvanabra]

You can buy pressure testing kits for not obscene money as well. I use this one:

Amazon.com: OTC (7991) Cooling System Pressure Tester: Gateway

Buy OTC (7991) Cooling System Pressure Tester: Fuel Pressure Testers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

and have been very happy with it. It's saved mountains of time finding external leaks. It's also helped me brace for an inevitable head gasket job once or twice.

An alternative is this thing:

https://www.amazon.com/OEMTOOLS-24444-Cooling-System-Refiller/dp/B01BW39HJS/ref=sr_1_2?crid=1PJNMKUIS3BYM&keywords=airlift+coolant+refill+tool&qid=1569858420&s=gateway&sprefix=airlift+coo%2Caps%2C189&sr=8-2

I use an older version called "Airlift" but same concept. You need a compressed air source to run it, but it's a great tool. First you vacuum the system down to 25" and let it sit for a while to be sure it isn't leaking air, then you stick a hose in a bottle of coolant and it vacuums the coolant right in.

In some ways, you "need" both tools... the vacuum tool is only useful when the system is empty, and in certain situations it may not uncover a leak as it can suck hoses together creating an artificial closure. The pressure tool isn't limited by these factors. The pressure tool also forces coolant "out" somewhere, so you can see where the leak is. Combined with a UV dye it's typically a slam dunk. I've had these things for like a decade and they've definitely paid off over time... zero instances of "I missed a leak" since I added them to the garage, and two instances of "mechanic can't find the leak, $500obo" cars I fixed in an afternoon.

 

[ansermet]

Thanks to all of you experts! I will see if I can get my "head" wrapped around all of this. To be continued.