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Coolant Loss

When my Mitsubishi Galant had 24,000 mileage in 2004, it was under warranty. The dealer noted on service records they:

“Repaired the split hose-water bypass” and “Repaired coolant leak at back of heater hoses”. No problems until this summer - 2009. Routine checks under hood have uncovered the resevoir either halfway, or 3/4 of the way empty every week. I have put in about a quart of coolant a week (Peak mixed 1/2 and 1/2 with water. I find no leaks at resevoir, radiator or hoses. A mechanic replaced the throttle body hose and clamp two days ago -today the resevoir level was halfway between “Full” and “Low”. At no time do I smell anything. I need help! Any suggestions?

Sincere kudos for monitoring your fluids. In all likelihood ou’ve kept your problem small by doing so instead of letting the engine overheat and having it turn expensive and ugly.

There are a few possibilities.

The way the system works is that as the coolant in the engine heats up it builds pressure until it reaches the pressure rating of the radiator cap (it’s marked in the cap). If it builds beyond that it pushes the excess fluid past the cap and into the reservoir. If the reservoir is full it’ll push the excess out the overflow tube on the side of the reservoir.

Then when the engine cools down and the coolant contracts, it’ll draw the fluid back out of the reservoir and the level will drop.

Your reservoire bottle should have a “cool” and a “hot” making molded into the side. Where the level is between thos marks is determined by whether the engine is cool or at running temp.

Now, the possibilities:
(1) you’re misunderstanding the level the bottle ahould be at. No offense, I’m just acknowledging the possibility.

(2) your radiator cap is not holding pressure. Replacement: $15+/-.

(3) your system is not holding pressure. You can have the syetem pressure tested.

(4) (low probablility IMHO) you have a headgasket leak. That can be verified with a check of the coolant for hydrocarbons and/or a pressure leakdown test of the cylinders.

The coolant leak in 2004 is irrelevant. Forget it.

Thank you for doing “routine checks under the hood.” If more people did them we’d have a lot less problems to deal with.

Having to add a quart of coolant a week indicates a serious leak, but you say no leak is evident. This is a conundrum. Where are you adding coolant; in the reservoir, or in the radiator? Where are you checking the coolant level; in the reservoir or in the radiator?

Samemountainbike: Thanks for the suggestions, esp. “You’re misunderstanding the level the bottle ahould be at. No offense, I’m just acknowledging the possibility.”…you could be correct, I could be misunderstanding the level.
Bear with me and respond to this.

  1. The Galant coolant resevoir has two markings: “Full” and “Low”
  2. I always check BOTH radiator and resevoir - after the car has sat at least 8 hours - usually in morning - in other words, when the system is COLD and I can assume no more coolant will flow either way.
  3. The Radiator is always full (to the cap) when I check.
  4. The Resevoir is either halfway between Full and Low, or below Low when I check.
  5. I add coolant/water (50-50 mix) to the Resevoir.

I forgot one thing. The mechanic the other day put on a new thermostat. He didn’t say he thought that was the problem, but thought it was a good idea to put a new one in.

So, he replaced a “rear throttle body hose” and clamp, and replaced the thermostat.

The work that the mechanic did on the throttle body caught my attention. Typically these are heated with coolant. Perhaps some coolant was lost during repair and not correctly refilled.

All you are doing is reading a level in a bottle,no other symptons.

If you’re putting coolant in regularly, you obviously are losing it somehow. So, there’s either a leak or a headgasket problem. If you see fluid under the car other than clear water from the air conditioning, there is probably a leak. If not, you may well have a cracked head gasket and be burning it.

Classically, a head gasket leak will manifest itself as a cloud of “white” (which looks gray to me) smoke from the exhaust – especially when you first start the car. it’s surprisingly hard to see such smoke from the driver’s seat unless there is a lot of it. So perhaps you can start the car on a warm dry day, leave it running in park, get out and look to see if there is a bit of smoke (steam actually) coming out the exhaust. If so, suspect a head gasket problem. Be aware however, that some weather/temperature conditions can cause some condensation from an engine running normally. If other cars also are emitting steam, you’ve picked the wrong day to try this.

Your mechanic should be able to pressure test the cooling system. That will aggravate any leaks and will very likely make it clearer where your coolant is going.

to old school, vtcodger and mcparadise: Thank you all.
You are correct : Only symptom is the coolant is low in resevoir. This is actually my daughter’s car for college. Typically she starts the car after I have checked everything. I find NOTHING on the ground, and see NOTHING out of the exhaust. I have also found NO leaks, at least not up front. Only symptom is, resevoir is low.
I guess I will have it pressure tested if it continues. One more question: How important is it to use “distilled” water? I have used bottled water 1/2 and 1/2 with PEAK Global antifreeze. Does it really matter? Is bottled water evaporating more than distilled would? Just asking, since I have used bottled and seen some posts elsewhere about distilled. Thanks to all.

The rate of evaporation should be inconsequential regardless of the type of water used. Water is water, the only difference between bottled water, tap water, and distilled water is the level of impurities, and they’re measured in parts per million. Its only path to evaporate out of is the overflow tube out the reservoir cap. It’s an almost closed system.

You are doing the correct thing in checking the radiator as well as the bottle. keep up the good work.

yeah, a system pressure check would, IMHO, be the next best step. That’ll tell you if you have a leak in the cooling system and help find it.

If a system pressure check shows nothing, checking the coolant for the presence of hydrocarbons and perhaps even a cylinder leakdown test (if the HC test isn’t definitive) may be in order.

Oldschool: I asked the mechanic about what you posted that perhaps a small amount of coolant was lost during repair. He said he replaced the rear throttle body hose since he saw a small leak there, and he agreed that when he replaced that hose and clamp, some coolant probably escaped. He did refill it, and said I might have to replace a small amount once or twice until the entire system is full, but then it would be fine. I added about a pint the day you posted your comments to me.
I waited 3 days more - until today - and twelve hours after being parked. The resevoir is near “full”, so it appears to have not lost any since the hose was replaced. Thank you.