Share This Page

Antifreeze smell could indicate leak

| Friday, Oct. 5, 2012, 9:19 p.m.

Q I have a 1998 Chevy S-10 and I am getting the smell of antifreeze coming from the air vents. It seems to be stronger when the heat is on. There is no antifreeze leaking anywhere in the engine or under the dash. The heater core hoses are tight, and they are both hot after warming up the engine. I recently bought the truck and a short time after that the A/C quit working. I don't know if that would cause the smell to occur. I would hate to replace the heater core if I am not sure that that is the problem. Any advice you can give would be greatly appreciated.

— Donn Dougherty

A Your thoughts about the odor coming from the heater core are well founded, as this is the only area within the truck cab where antifreeze exists. It's possible also, but less likely, that leaking coolant odors are coming in with the ventilation air from an under-hood leak.

Typically, when a heater core begins to leak, one may notice fogging of the windshield when using the defroster; damp-slimy carpet beneath the right/center of the instrument panel; and a citrus-like odor, similar to what you've described. There would also be a loss of engine coolant, but the rate may be less than you'd expect — it only takes a pint or so of leakage to create the above symptoms — and this might not be immediately evident looking at the coolant overflow bottle level. A leak from under the hood should be easy to spot on the ground.

Your heater core is a cigar box-sized mini-radiator that transfers engine heat to the passenger compartment via circulating engine coolant. This part resides deep within the heater/ventilation system, and most aren't very pleasant to renew, as quite a bit of instrument panel disassembly is often required. Most heater cores are made of thin-wall aluminum, with a large network of finned passages that provide maximum surface area for heat transfer. Over time, accelerated by deferred cooling system maintenance, internal corrosion will find a weak spot, and pressurized coolant will begin to seep into the surrounding housing, and eventually to the carpet beneath.

I have a hunch your heater core might have a tiny leak, and most of the liquid may be vaporizing, causing the odor, or hasn't yet reached a seam of the heater housing. To be sure, you might need to drill a small hole in the lowest part of the plastic housing. Slide a piece of hose or tubing on the drill bit so it can't bore more than one-quarter inch deep — you don't want to cause new problems. Then, after shutting off the fully warmed up engine and waiting perhaps 15 minutes, check for signs of coolant leakage at the test location. Even one drop of coolant means trouble.

You could buy some time by adding a single dose of Bar's Leaks or AlumAseal, which should close up a small leak at least for a while. Your S-10 heater core is about average in replacement difficulty, taking 3 to 6 hours depending on skill level, tools available and fortitude.

I can't fathom how the air conditioning working or not would be a factor regarding this odor. Refrigerant is odorless, should leakage occur. It's likely a coincidence the A/C has recently quit.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at under-the-hood@earthlink.net; he cannot make personal replies.

TribLIVE commenting policy

You are solely responsible for your comments and by using TribLive.com you agree to our Terms of Service.

We moderate comments. Our goal is to provide substantive commentary for a general readership. By screening submissions, we provide a space where readers can share intelligent and informed commentary that enhances the quality of our news and information.

While most comments will be posted if they are on-topic and not abusive, moderating decisions are subjective. We will make them as carefully and consistently as we can. Because of the volume of reader comments, we cannot review individual moderation decisions with readers.

We value thoughtful comments representing a range of views that make their point quickly and politely. We make an effort to protect discussions from repeated comments either by the same reader or different readers

We follow the same standards for taste as the daily newspaper. A few things we won't tolerate: personal attacks, obscenity, vulgarity, profanity (including expletives and letters followed by dashes), commercial promotion, impersonations, incoherence, proselytizing and SHOUTING. Don't include URLs to Web sites.

We do not edit comments. They are either approved or deleted. We reserve the right to edit a comment that is quoted or excerpted in an article. In this case, we may fix spelling and punctuation.

We welcome strong opinions and criticism of our work, but we don't want comments to become bogged down with discussions of our policies and we will moderate accordingly.

We appreciate it when readers and people quoted in articles or blog posts point out errors of fact or emphasis and will investigate all assertions. But these suggestions should be sent via e-mail. To avoid distracting other readers, we won't publish comments that suggest a correction. Instead, corrections will be made in a blog post or in an article.