Lost coolant and getting fog inside windshield

RANGERFANATIC

MEMBER
1997 FORD RANGER
3.0L
6 CYL
2WD
MANUAL
465,000 MILES

I bet I get a couple responses telling me I need to get a new truck with the miles I have but it runs good. Problem, for several years I smelled coolant when I turned on the heater, but I waited to deal with the problem until it got so bad it started fogging up the inside windshield. I had a shop replace the heater core about six months ago and everything was fine until I went on a 1,500 mile trip, then I started smelling the coolant again and the window started fogging up. I took it back to the shop that did the work and he said I lost one to one and half gallons of coolant and it must be a head gasket leak not the heater core. The truck does not over heat and runs good, no rough idling. He said compression test showed no leak down, changed oil, no milky oil. Coolant in the radiator does not show any oil in the coolant. Said he did a dye test and it turned yellow and did a six point analysis and it showed 20PPM of Oxygen and 9ppm of HC in the radiator. I had a safety check done before I left on vacation and was told everything okay. So how do I lose this much coolant in five days and 1,500 miles? I think it is the heater core again and not a head gasket as the mechanic claims. He says the gasket leak caused pressure to build up and is causing the heater core to fail. Any ideas?
Charles

8 Replies

STEVE W.

MECHANIC
13,463 POSTS

Any amount of hydrocarbons in the coolant system is a bad thing as it only has one possible source. From the numbers I would say you have a small head gasket leak, it may get worse when the engine gets hot. The interior fogging could be a bad core (could test that yourself if you want proof. Just "rent" a cooling system pressure tool and use it to put 15 psi of pressure on the core through the heater hoses. If it leaks down either the core is bad or the connectors are leaking.

I see a couple options depending on how much you want to spend and what shape the rest of the truck is in.
If the truck is in very good shape other than this issue and I owned it I would probably drop a reman engine in it and replace the heater core with a unit sourced from the OEM maker.
Or as it sounds like it's a small leak you could get a jug of Blue Devil - Head Gasket Sealer (original not the pour and go stuff) and follow the directions, especially the flush with clean water before adding it to the system. I have used it a few times to get some extra miles out of a vehicle without tearing it down. Never had it plug a heater core or radiator unlike some of the other types that use metal flakes or walnut shells.

Or buy a new truck, LOL. (Well you do have that option, but I will say most of the newer stuff is a bear to work on compared to your 1997).

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Wednesday, March 28th, 2018 AT 4:33 PM

RANGERFANATIC

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5 POSTS

Thanks Steve,
Was hoping with the indication of the heater core leaking again that was the problem, not the head gasket. Especially since the pressure test didn't show a leak down and the mechanic didn't say he had pulled and checked the spark plugs for coolant deposit. I am going to buy a dye test myself and see if it shows a leak. May get a second opinion on the 6 point machine analysis.
I have a gravel driveway where I park so hadn't noticed leaks on the ground especially with the rain we have been having.
Truck has no dents and cab is good except for the seats and one of the few trucks with a 7ft bed. Was hoping to make it to 500,000 ha ha. I have a 2004 with same engine sitting ready for when this one dies just doesn't have the 7ft bed.
Charles

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Wednesday, March 28th, 2018 AT 4:55 PM

STEVE W.

MECHANIC
13,463 POSTS

A coolant pressure test may not show a bad head gasket if it only leaks a small amount. Those tests use 10-15 psi while combustion pressures are much higher and could push through a small leak that the lower pressures cannot. I have also seen "one way leaks" where the gasket had failed and would let combustion pressure out but on the intake stroke with the cooling system pressurized it did not leak. Those can drive you nuts!

I use three methods for head gasket testing, the coolant pressure test, then the liquid test (you can rent the tester at many parts stores, you just buy the test fluid) and 99% of the time I use an electronic combustion gas tester, either my five gas unit or the smaller one that detects only a couple gases, neither one of which should be in the cooling system. I have seen those as "loaner tools" as well. Oh, FYI the loan a tool system in most stores = you buy the tool from the store at full price, when you return it in the same condition, they give you the money back, less the charge for any consumables.

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Wednesday, March 28th, 2018 AT 7:03 PM

RANGERFANATIC

MEMBER
5 POSTS

Steve, thanks again.
Local Grand Auto, couple young kids working there said they loaned tools but did not have this one. Will try another place.
One last question related to original problem. I think the new heater core or the hoses are leaking. The mechanic who did it six months says it is the head gasket leak caused it by allowing too much pressure in the system, yet the truck is not over heating. Is he correct? Can that be the reason the heater core is leaking again?
Charles

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Thursday, March 29th, 2018 AT 8:18 AM

STEVE W.

MECHANIC
13,463 POSTS

High pressure in the system can easily pop open a heater or radiator core. They are designed to handle at most 20 psi. The combustion pressures are in the hundreds of pounds. Sort of like blowing up a balloon a small puff at a time. Eventually the pressure will pop the balloon.

That is one issue with the loaner tools, finding a store with them. Worst case would be to buy one, might be cheaper than burning gas. These are a few item numbers.

Lisle 75500.
Block Tester BT-500 or Block Tester BT-700.