losing antifreeze

[Bobg]

I have a issue with losing antifreeze, Can't find any leaks, cooling water is coming out the back and appears to be clean, (thinking the heat exchanger was leaking), no antifreeze in the bilge, no leaks under the engine.  but it does slowly go down in the reservoir,( the reservoir on the engine,) (not the plastic overfill bottle).  After about 4 hours of motoring, I am down about a 1/4 inch in the reservoir.
Is there a possibility I am leaking a small amount into the cylinders and burning it?

I found out about the problem because after motoring for a few days without checking it, the temp gauge started to go up, ( I didn't know I had a problem at the time), the reservoir was close to empty when I did check it.  (I know, I know, I should check these things everyday, but as the days go by, and nothing changes,  I got a little lax and it bit me)
any advise would be appreciated.  Thanks guys  Bob

[Bobg]

Forgot to add, I don't have any evidence on my oil dipstick.  Oil looks good, and when I changed the oil, the same amount came out that always does when I change the oil.  So I am confident, the antifreeze isn't leaking into the oil

[KWKloeber]

I have a issue with losing antifreeze, Can't find any leaks, cooling water is coming out the back and appears to be clean, (thinking the heat exchanger was leaking), no antifreeze in the bilge, no leaks under the engine.  but it does slowly go down in the reservoir,( the reservoir on the engine,) (not the plastic overfill bottle).  After about 4 hours of motoring, I am down about a 1/4 inch in the reservoir.
Is there a possibility I am leaking a small amount into the cylinders and burning it?

I found out about the problem because after motoring for a few days without checking it, the temp gauge started to go up, ( I didn't know I had a problem at the time), the reservoir was close to empty when I did check it.  (I know, I know, I should check these things everyday, but as the days go by, and nothing changes,  I got a little lax and it bit me)
any advise would be appreciated.  Thanks guys  Bob

Is she dropping while running?  If so most likely a pinhole between the sea water and closed coolant sides.  How old is the Hx?

If you relieve the pressure (crack open the pressure cap) you'll lose less coolant. The coolant will always move from the block to the sea water exhaust, not vice versa.

Also If you have no pressure in the domestic water system coolant can also migrate to there through a pinhole in the water heater coil.
If you have the wherewithal you can put a little water or air pressure on the sea water side of the Hx to verify whether there's a pin hole leak or if it holds pressure.

Ken K

[Bobg]

Thank you Ken, I have not done a pressure check on the hot water tank or the heat exchanger, I was looking at the water discharge for a hint of antifreeze.  I think you mean, removing the engine coolant hoses from the heat exchanger and try to put a pressure test on the heat exchanger via the hoses, and a gauge, with air and watch for a pressure drop.  I will investigate that option.

I wish there was a way to test the discharge water for minute amounts of antifreeze.


I did notice my overfill reservoir, the plastic bottle, seem to get fuller and does not go down when the engine is cool. I did take Rons advice and angle cut the hose a long time ago.  Another thing to investigate

[lazybone]

When the engine is running up to temperature,  do you get any air bubbles in your overflow bottle or in the heat exchanger while you observe the coolant flow with the cap off?

[anaisdog]

I have the same issue with a reseviour put on, last year.  it hangs in the head since my 1986 did not come with one.  it's leaking and i can't tell from where.  It's not a huge leak at all but it is going down, even with the engine not running.

[Stu Jackson]

We have an M25, I think Bob has an M25XP.  I added the "Ron Hill Rubbermaid coolant bottle" with the angled cut at the bottom of that hose, too.  

Long story:  we'd been losing a considerable amount of antifreeze a year or so ago, changed all the hoses, still leaked, ended up writing it up here as a leak in the shell of the HX caused by a busted bracket, replaced with new HX.  I'll find the link.

Here it is:  http://c34.org/bbs/index.php/topic,6920.0.html

Since then, I've been running the engine quite a LOT this summer, and found what Bob originally posted, although my Rubbermaid container is so old it's black now and needs to be replaced!    I can't even see the level!!!

Anyway, everything else is fine, so I just keep topping up the manifold, NOT the coolant bottle, with a cup or two of distilled water alternated with antifreeze and the temp is just fine.

Bob, check the usual suspects first, doesn't sound like a big problem.  In fact, I found that if I left it with a topping up that the level in the manifold will steady out a tad down from the top.  I also have a new water heater and hoses, so that ain't it either.    

Try that first before you go gaga.  Good luck.

[dfloeter]

Sort of on this topic, my coolant cap is leaking from the underside seal and might someone have an aftermarket part number?
This is the M35 AC 1996 model. 
Thanks Dietrich

[Ron Hill]

Bob : From your write up it sounds like you have a "coolant recovery bottle", but you are taking off the engine cap to check the coolant level?

You could have a simple leak in the hose from just under the cap to the bottle.  Maybe just tighten the hose clamp that holds the hose on to the nipple under the cap?  

The whole idea of a coolant recovery system is so you don't have to remove the cap from the engine - just like your auto.  The fluid goes into the bottle when it expands and flows back into the engine when it cools.

A thought

[Aries]

Sounds like you're losing coolant into the exhaust. A pressure test will help you find your leak. First attach a pressure tester to the radiator tank neck and pump it up to 10 to 12 psi. If the pressure drops you have a leak somewhere. If there is a leak but you don't see coolant leaking anywhere, then either the heat exchanger, the coolant tank, or the head gasket is leaking. Remove the hose from the heat exchanger to the mixing elbow and pressure test again. If coolant runs out of the heat exchanger hose, the heat exchanger is leaking and must be replaced or repaired. Otherwise the tank is cracked and coolant is leaking into the exhaust manifold. If the engine is running OK and the oil level is stable (it's not "making oil") then it's unlikely the head gasket is leaking.

[Bobg]

Thank you everyone, will try pressure testing, sounds like it is a not uncommon scenario.  I lose about a 1/8 of a inch in the manifold after about 4 hours of running the engine.  Ron, my coolant bottle doesn't seem to go down, however increases in volume.
  If I didn't check the manifold, I would get a false assurance that I am full of coolant for the engine. When I first noticed the problem, My manifold was empty, while the coolant plastic bottle was full. so at this time,I do check the manifold for assurances until I can figure it out.

shouldn't the Tupperware bottle suck back to the manifold while it cools down?  like on my car.The hose from  the barb under the cap to the overflow bottle is tight and the hose SEEMS ok. but I think I better check it for a minute hole when I get back to the boat where it may suck air instead of coolant back to the manifold.

Maybe I don't have a leak, but the coolant is transferring to the bottle and not returning???

I don't know guys, but will check all that has been advised, and thank you all

[Craig Illman]

You might just need to replace the cap. The outer cap seal may leak air, so when the coolant in the engine contracts, it sucks air, instead of lifting coolant out of the bottle. Also, you don't need to go to Westerbeke to get a new cap.

[KWKloeber]

It's not even necessary to have a pressure gauge. Use the seawater side of the Hx to pressure test.  Block off one hose securely (say a bolt clamped tight in the hose). Even a bicycle pump is enough - a couple psi into the sea water side - if it holds, bingo.  If it doesn't, bongo. No need for pressure cap adapters and gauges etc.  Crack open the pressure cap just to ensure you have no residual psi you're working against.

Cheap to replace the peasure cap (Autozone) to ensure the overflow/reservoir isn't part of the problem.  If the reservoir is filling (sounds like that's not the issue) and not sucking back, it could be the cap.  More likely, its the Hx - when the block overheats, it pushes out both the Hx pinhole and past the cap into the overflow (too much volume/pressure for just the pinhole to handle it).  But on refilling the pinhole is enough to prevent a vacuum from forming to suck coolant back into the block.

Ken.

[Ed Shankle]

Bob,
Another consideration is the exhaust manifold gasket. There is a very narrow strip between the coolant tank and the exhaust port. Could be a dribble occurring across the gap. If you've got a good nose, you may be able to smell the coolant in your exhaust; it's a sweet aroma, if you haven't experienced it before in your car or boat.
Good luck exploring all these potentials...

Ed

[Ron Hill]

Bob : From what you've said the expanded coolant is flowing into the recovery bottle. But you have an air leak as the coolant is not being sucked back in the reservoir. 
I believe that you have a coolant recovery problem, not a HX or head gasket or other problem!!

Here are a couple of things to check:
1. Get some new tubing - I liked the clear
2. Make sure the small hose clamp is not cutting into the tubing - I used some thin leather as a cushion between the clamp and the tubing.
3. Make an angled cut so the tubing will just touch the bottom of the bottle - the angle cut insures it can't get sucked to the bottom of the bottle.
4. Insure that the cap on the bottle top is NOT air tight, so air can move freely out when the bottle fills and air can come back in as the coolant is sucked back in to the engine.
5. Install the bottle so it is level with or slightly below the outlet under the pressure cap.

I'd fill the bottle only about half full when the engine is cold.

A few thoughts