too much moisture in exhaust?

delco1946

delco1946

Senior Member
Wondering how much moisture is acceptable in exhaust at start up? I have enough to discolor (wet it) the pavement under both exhaust tips after the fist couple minutes of startup. This dissipates of course as it warms up.

I've never noticed anything weird in my oil which i would think i would if coolant was leaking somewhere it shouldn't.
 
That situation is normal. Water is a by-product of combustion. Gasoline is a hydrogen compound (hydrocarbon) and burning hydrogen produces water in vapor form. When the exhaust pipes are cold this vapor condenses on the pipe walls and drips out as a liquid. When the system warms up the water stays a vapor. On cold days the vapor forms a "cloud" at the tailpipe.
 
Yep, normal, if my 3 old Fords are any indication. Can happen even in warmer weather at times. However, it does show how much condensation can end up in your muffler and exhaust if you don't warm up the engine enough to get rid of most of it.

To check for coolant in exhaust vapor, I just put a white paper towel under the tailpipe and let it get damp. Then I check it for coolant smell or color.
 
I suggest drilling a 1/8" diameter hole at the low point of the bottom of each muffler and also drilling another 1/8" hole at the bottom of the tailpipe at the corner before the pipe turns upward to go over the rear axle.
Doing this will allow the condensation to drain out rather than to be trapped and start rusting out your exhaust system components.
 
This brings to the front the need to "heat soak" the systems on these old cars. Engine, transmission, rear gear and the exhaust system. As stated the moisture is normal, the exhaust tubes not being warmed up allow the moisture to collect. Drilling the holes will eliminate some of the moisture but introduces another problem. Perfect place for rust to start and of course the exhaust gasses possibly getting into the passenger compartment.
 
Many, if not most, modern exhaust systems incorporate drain holes. If they don't have 'em they're likely made of stainless. Holes of proper size and placement don't present a problem with exhaust gasses entering the passenger compartment unless there are holes in the floor. The rust issue associated with drilling can be addressed with cold dip galvanizing sprayed into the holes.
 
The higher the humidity level, the more condensation will happen with temperature differential. If the coolant level is not changing then any leakage would be negligible. If a head gasket leaks or a crack forms then the coolant temps will rise and coolant loss will be notable.
 
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Dobie Gillis said:
Many, if not most, modern exhaust systems incorporate drain holes. If they don't have 'em they're likely made of stainless. Holes of proper size and placement don't present a problem with exhaust gasses entering the passenger compartment unless there are holes in the floor.
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Weep holes are incorporated into most muffler assemblies. They are factory engineered, not punched by a car owner. And there are holes and seams in the floor pans and seal leakage at a gate or deck lid. An older vehicle will most likely have a porous floor board.

Putting a weep hole into an actual inlet pipe, intermediate pipe or exhaust pipe is just begging for MR. SANDMAN (and his close friend CO) to pay you a little visit.

But the nice thing is you may never realize it ... :cool:
 
This is an interesting topic. Short trips are notorious for ruining mufflers and rusting out exhaust systems before their time. Old duffers who drive a half mile every day for their coffee club. "Damn mufflers, they don't make 'em like they used to!" is the refrain. That's not how this works. That's not how any of this works.

Frequent short trips also tend to load up the crankcase and engine with condensation and sludge, which combine with raw fuel and other contaminates to form corrosive acids over time, can see this in etched crank and rod bearings. The best solution of course is to drive them!

Many years ago an SAE engineer named Bob Sikorsky wrote a book called "Drive It Forever" and discussed this at length, he was insistent about regular and frequent oil and filter changes, but he also stressed that it's very important that an engine reach "Normal Operating Temperature" or NOT as quickly as practicable.

No load idling will not do this, and short trips won't do this. A defective or incorrect cooling system thermostat also is a common cause of engine sludge and excessive wear and crankcase oil "loading up". A brief highway run of maybe 15 minutes to a half an hour or so on a well tuned engine will drive off most all crankcase condensation and potential sludge, the final drive of the season before putting collector cars away for say 6 months or longer especially should be long enough to reach "NOT" and boil off condensation and sludge.
 
I agree 100% that short trips are bad for a car, nevertheless, short or long trips, there is going to be condensation, at least initially. My guess is that condensation will "steam out" of the tailpipe on longer highway trips and do little to damage a quality exhaust system.

As for the 1/8" hole in bottom of mufflers, etc, I have no concern about exhaust gasses entering the passenger compartment. I had to cut out and weld in all new floor pans in both my cars and each seam is extensively sealed to prevent rust or water seepage in case I ever had to drive thru a flood.
If your car is factory original or an older restoration and you are worried about exhaust gas, you might want to pull up the carpet or floormat and inspect seams and floor-plugs, but I doubt exhaust from a 1/8" hole is gonna fill the passenger compartment unless there is a giant rust hole in the floor right above the muffler.
 
... but I doubt exhaust from a 1/8" hole is gonna fill the passenger compartment unless there is a giant rust hole in the floor right above the muffler.
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You really need to add IMO with this statement as it is not 100% correct in anyway. You are implying your personal beliefs on others that may not be more familiar with how an auto actual operates and the consequences thereof.

This is why ANNUAL STATE VEHICLE INSPECTIONS are in place, to keep morons from killing themselves, family or the motoring public.

It is right up there with drilling a vent hole in a gas filler cap, not too wise.
 
delco1946 said:
Wondering how much moisture is acceptable in exhaust at start up? I have enough to discolor (wet it) the pavement under both exhaust tips after the fist couple minutes of startup. This dissipates of course as it warms up.
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What is the relative humidity in OR.?
 
A brief highway run of maybe 15 minutes to a half an hour or so on a well tuned engine will drive off most all crankcase condensation and potential sludge ...
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IF the vehicle has a properly designed/operating CLOSED PCV SYSTEM. ROAD DRAFT is not going to provide it.

Neither will a 160 degree coolant thermostat.
 
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