350 coolant disappearing

[Steven Petersen]

Trying to track down the coolant loss on my 88 350. I pulled the spark plugs yesterday and see no sign of burnt coolant. I’m gonna do a compression test this morning. If that doesn’t show any irregularities, what’s next? Everybody seems to think it’s a head gasket. I want to be damned sure before I dive into the heads. Not feeling good about removing exhaust manifold bolts from a 35 year old engine that have most likely never been off.

 

[CKVortec]

what I generally do when I suspect a head gasket failure (if a compression test isn't definitive) is to do a cooling system pressure test with all the spark plugs removed. You will be able to see the pressure drop in the system and if you keep applying pressure long enough (don't go over about 15 psi) you will find the coolant leak. It will either be on the floor, under the dash from the heater core, in the oil pan, in one or more cylinders, or in the intake, or exhaust.
after about 5-10 minutes of pressuring up and looking for leaks if you haven't found anything turn the engine over with a wrench and look for coolant coming out of the spark plug holes.
The punch line is: the coolant is going somewhere, it's up to you to find it.

 

[PlayingWithTBI]

I’m gonna do a compression test this morning

When I did my compression test the 2 cylinders, that showed they were burning water, were only 5 psi lower than the rest.

 

[RichLo]

you can get a coolant system pressure test kit and pressurize the system without the engine running to check for leaks or noises and measure the rate (time) at which it looses pressure.

 

[Steven Petersen]

you can get a coolant system pressure test kit and pressurize the system without the engine running to check for leaks or noises and measure the rate (time) at which it looses pressure.

This sounds like what I need if the compression test doesn’t give a clear answer.

 

[HotWheelsBurban]

What does the motor oil look like? And the transmission fluid (is the truck an automatic or manual)? If either of them looks like chocolate milk, your coolant is mixing with them. Oil is likely a head gasket, or intake manifold gaskets. Though the latter is more common in vortec engines. Transmission fluid is only close to the coolant in one place: the trans fluid cooler/warmer(for cold weather on startup) in the bottom of the radiator. On old radiators this can corrode and deteriorate, then the fluids mix.
I accidentally ran my Burb almost dry(forgot to check the level a couple days, I check religiously every morning now!). Got orange milk oil, from the DeX cool, and changed oil and filter. Put a bottle of Bars Leaks copper in it, and so far, so good, a year later. Ran water in it over the summer, but regular antifreeze is in it now.

 

[Steven Petersen]

What does the motor oil look like? And the transmission fluid (is the truck an automatic or manual)? If either of them looks like chocolate milk, your coolant is mixing with them. Oil is likely a head gasket, or intake manifold gaskets. Though the latter is more common in vortec engines. Transmission fluid is only close to the coolant in one place: the trans fluid cooler/warmer(for cold weather on startup) in the bottom of the radiator. On old radiators this can corrode and deteriorate, then the fluids mix.
I accidentally ran my Burb almost dry(forgot to check the level a couple days, I check religiously every morning now!). Got orange milk oil, from the DeX cool, and changed oil and filter. Put a bottle of Bars Leaks copper in it, and so far, so good, a year later. Ran water in it over the summer, but regular antifreeze is in it now.

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Engine oil is perfect, although it’s only got maybe 300 miles on it. No evidence of coolant when I drained old oil. Tranny fluid a little dirty, but no evidence of coolant. 700R4 transmission.

 

[kenh]

There is also a "kit" that will test for combustion byproducts in the cooling system.

Does the engine drop a cylinder on a cold start? A large enough leak into a cylinder will have this.

I'm assuming there are quite a few miles on the engine. It seems a warped head is usually the case. At least it is not an uncommon problem. If you do pull the heads DO have them checked for strait and flat in addition to cracks.
https://pmmonline.co.uk/technical/blown-head-gaskets-how-to-detect-them/

https://www.ebay.com/itm/3238261609...AEOzyrlitBlsyRs4cuNEW5hGOXB9dXnkaAqwXEALw_wcB

 

[Steven Petersen]

There is also a "kit" that will test for combustion byproducts in the cooling system.

Does the engine drop a cylinder on a cold start? A large enough leak into a cylinder will have this.

I'm assuming there are quite a few miles on the engine. It seems a warped head is usually the case. At least it is not an uncommon problem. If you do pull the heads DO have them checked for strait and flat in addition to cracks.
https://pmmonline.co.uk/technical/blown-head-gaskets-how-to-detect-them/

https://www.ebay.com/itm/3238261609...AEOzyrlitBlsyRs4cuNEW5hGOXB9dXnkaAqwXEALw_wcB

It misses or stumbles 3 times on average during the first 30 seconds of a cold start. Usually only if it’s below freezing. After that it runs perfectly.

The pickup only has 50,000 miles on it. I purchased a year ago from the original owner. He gave me documentation to back up the mileage. He bought it for his business in 1987. Shut down and retired in 88. After that just kept it as a hunting vehicle. There’s literally receipts showing oil and lube service with only a few hundred miles between service.

 

[DerekTheGreat]

...The pickup only has 50,000 miles on it. I purchased a year ago from the original owner. He gave me documentation to back up the mileage. He bought it for his business in 1987. Shut down and retired in 88. After that just kept it as a hunting vehicle. There’s literally receipts showing oil and lube service with only a few hundred miles between service.

Age adds it's own kind of mileage.. Which is why I like to go for vehicles with a bunch of miles on 'em. Vehicles that sit around end up with problems once you start flexin' their muscles so to speak. If the vehicle in question has high mileage but checks out overall, don't hesitate on snatching it up. Feel good about the money you saved too. The low mileage thing is a fool's errand unless you want another flower pot sitting in the garage. My truck has 255k on it, wife's has 215. You'd never know unless you looked at the odometer, or paint.