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Burning Antifreeze at Startup

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Gregory

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"From a previous post,
I have

"From a previous post,
I have twin 1993 4.3L Mercruisers with fresh water cooling. Last year I noticed "some" coolant buring during startup - you can smell coolant burning. During thw winter I replaced the risers with new close off gaskets between the risers and manifolds. Manifolds looked OK - no obvious signs of deteriation - So I just did the risers. Note that both the manifolds and risers are fresh water (antizreeze) cooled. I understand how the closed system work, but I'm still getting coolant burning at startup this year too. No water in the oil, so it must be the manifolds and/or manifold gaskets? No? Even if I pressure test them, how will I know which one to do - if indeed it is the manifolds - or should I just do both - makes sense to me. But I can't get out of my mind that the ONLY reason you should get coolant burning during a cold startup is becuase coolant has dripped down into the manifolds - but the gaskets are new - and torqued to the specs of 26 ft-lb. Anyone have some trouble shooting ideas? Thx."
 
risers are raw water cooled. t

risers are raw water cooled. the water exiting the heat exchanger exits thru the riser.manifold may or may not be fresh water cooled.depends on the plumbing.where do you smell the A/F?
 
"Greg
Most likey a head gaske

"Greg
Most likey a head gasket leak, small but there. What happens is that small amount leaks into cylinder then burns off when started."
 
"For a quick test, see if you

"For a quick test, see if you can get an auto service center to check your antifreeze for exhaust gases with an analyzer to rule out a blown head gasket. How much antifreeze are you losing?

When the engine is stone cold, pull the plugs and examine them closely for anti-freeze or color differences. If one or more plugs are wet or discolored , they are the culprits--blown head gasket or cracked water jacket in a head or block. If there are not any, then it could be the intake manifold gasket. You can do a compression test or leakdown test to see which cylinders are involved."
 
"Lots of ideas but start with

"Lots of ideas but start with easiest, coolant hoses leak/drip/ooze at connection. One or two drops of coolant can amaze you on how mucn smell it can make, especialy if there is any antifreeze involved. Check any drain petcocks and hoses going to any fitting. Check engine water pump weep hole. How often do you have to add water, that would give you an idea on size of leak if engine coolant is involved. (closed system)
Also, any spark plug running with a coolant leak will be very clean compared to normal run plug."
 
"Wow! Thanks everyone for all

"Wow! Thanks everyone for all the quick feedback. Here's a bit more information:
Q: "where do you smell the A/F"?
A: From the exhaust out the leg. Definite white smoke with that antifreeze smell. Most noticable during cold start, but does show some signs with warm start. Gradually goes away after a few minutes.

Q: "How much antifreeze are you losing?"
A: About 1 litre per 5hrs running. Maybe a little less.

Q: "You can do a compression test ..."
A: I did last year before I replaced the risers and it was 155 - 160 across all 6 cylinders as I recall, but good idea, I'll check that again.

I'll also pull the plugs 1 by 1 and let you know. I was meaning to do that too, just haven't got around to it. The plugs were new this season along with wires, rotor, and cap.

Thx"
 
"Just don't run the motor

"Just don't run the motor before you pull the plugs. After letting it sit overnight, remove the coil wire and crank it over first. This will give you a 'signal' (antifreeze on the plugs) where running the motor first would burn it off.

Good luck, and I hope it's not a head gasket.

Jeff"
 
"... actually, if anything I h

"... actually, if anything I hope it is just the head gaskets, and not a cracked head and/or block. Good idea on turning it over with the coil wire removed. What I also do is to disconnect the electronic fuel pump too.

Thx. again. Will let you know. I hope to get around to it this weekend if the weather cooperates.

Greg"
 
"1 litre in 5 hours is a consi

"1 litre in 5 hours is a considerable amount if being run through a combustion chamber. The plug/s involved WILL BE be squeeky clean. Plugs not involved will be dirty. Another quick test is to open the filler cap on the heat exchanger WHEN ENGINE IS COLD, start engine and let it idle to operating temp and watch for bubbles (small leak or small crack in head) or back pressure from combustion chamber (major leak from water jacket to comb chamber) to push coolant out of filler hole. If neither is happening, look for hose leak or just put permetex on all the hose connections and clamp tight and dont forget to watch for coolant leaking out of the engine water pump weep hole or pulley shaft.
I had a leak sim to yours and it was a hidden drain valve dripping about one drop per 10 seconds.
Last, do you have alum head/s? Alum heads are problematic and should be outlaw'd. They are very heat sensitive and warp easy. I have done countless gasget changes on alum heads that just got close to overheating, warped and broke head gasget seal, cooled down and when removed, warp was gone, just installed new head gasget and all was ok."
 
"Actually it's probably mu

"Actually it's probably much less than that. I just recall filling it up with about a litre of 50/50 coolant after the first few weeks of the season. So maybe 20 hrs.

Anyway,

I pulled the plugs and checked them for wetness and did a compression check at the same time. I let it sit overnight, disconnected the ignition coil and fuel pump and cranked it for about 10 - 15 seconds, then started pulling plugs one at a time. Here are my results in firing order:

1 - 155 psi, slightly wet, not sweet tasting
6 - 155 psi, slightly wet, sweet tasting, coolant
5 - 155 psi, light oil, clean, not sweet tasting. Note that upon removing this spark plug pressure was released from the cylinder. I wonder if I also have a sticking lifter - anyway.
4 - 125 psi, clean, some oil. Note that I replaced the o-ring after doing this test since I noticed it had separated from the unit and may explain the slightly lower compression.
3 - 125 psi, dry and clean
2 - 150 psi, light oil, no obvious signs of antifreeze

Rear
6 5
4 3
2 1
Front

The order I actually checked them in was 2,4,6,5,3,1

So all I can really see is that number 6 did have some coolant on it - regardless of how much, some was there. So am I looking at a head gasket? Keep in mind that the sparked plug here did not look washed, it had some carbon buildup on it.

Also, after replacing the plugs, I started it with the heat exchange cap off and let it warm up to temperature. Steam/coolant again smoked from the exhaust, but there were no bubbles in the heat exchanger.

Suggestions for what's next?

Thx."
 
"Usually with a cracked head,

"Usually with a cracked head, the crack will expand at temp and cause worse coolant burning but since you said the smell and steam goes away when at temp. Im leaning towards a leak in the gasget between riser and manifold. Coolant could very well leak into the manifold and if leaks for a long enaugh time, it is possible to get into a cylinder depending on the design and shape of manifold and which exhaust valve is open when engine is not running.
Anyway, if you have not already done it, check all riser and manifold surfaces for flatness and make sure there is no foreign material of any kind on these surfaces and use a good sealer (permatex) on all sides of both sets of gasgets.
Check flatness with a straight edge and a .0015" feeler gauge.
Your manifold and riser surfaces will have some narrow webs and coolant channels, there could be burrs or raised edges caused by rust and crud that must be removed.
Althogh there are only probably 4 bolts on each assembly (assum its a v6) you must snug down then tighten and torque evenly. Snug each bolt the same amount, then torque in diagonal pattern, no more than 10 ft lbs per pass until you get to final torque then repeat final pass at max torque. The idea here is to GUARENTEE this will not be a source of your problem in case this does not solve your problem.
If you tighten one bolt at a time, it is very possible to torque a warp in your assembly."
 
"Bill,

Thanks for the feedb

"Bill,

Thanks for the feedback. Last year I did replace the risers and the close-off gasket between the riser and manifold. At that time, I inspected the manifolds and they appeared to be fine so I didn't replace them.

I did clean both surfaces very well, The old gasket did have a sealant on it which I had to scrape off with a razor, then used acetone to clean the surfaces. The new risers come with a primer coat on the surface from the factory that also must be removed with acetone which I did.

I did NOT replace the riser bolts - but am thinking maybe I should have since the threads may have stretched. I did torque them in proper sequence to 26 ft-lb as per the specs.

I was told by a mechanic to NOT use any sealant between the surfaces and the gasket and to put it on dry. Maybe I'll crack them off again, get a new gasket (because I didn't really like the one the Osco risers came with), new bolts and torque them down again and see what happens.

Unless anyone else has any other suggestions?

Thx."
 
"Normally you not need sealant

"Normally you not need sealant on surfaces that are perfect, but yours are old, somewhat deterioted and it would not do anything but help quarentee a good seal. Use permetex.
Use the old bolts and permetex them also.
Do your best at determining flatness on all surfaces.
This may seem a redundant proceedure but these gasgets are cheap compared to a r&r head job because the risers did leak.
Do you have alum heads? More on this after results of gasget fix.

Just a note..
I have worked on salt water rigs in that rust in this area have lifted the risers."
 
"Thanks Bill.

Do you recomm

"Thanks Bill.

Do you recommend a specific permatex product. (http://www.permatex.com/products/automotive/automotive_gasketing/gasket_sealants .htm)?

I know they make different gaskets for the risers too. One is like a paper outer core with steel inside and the other is a complete carbon gasket. I think I prefer the carbon gasket - but I'm not sure how this gasket takes a sealant. Ideas?

... do you mean "have lifted the risers" to imply that rust from the manifolds can get up under the riser/manifold gasket and lift the riser, or something else?

Thx again."
 
"Permatex form-a-gasget
Reaso

"Permatex form-a-gasget
Reason is the silicone stuff has to be applied to almost new metal for it to adhere properly.
Permetex will stick to anything and flow into flaws and will seal over greesy fingerprints, gas etc. Also, in situations where you are upside down hanging in a engine compartment playing twister with pan or timing chain cover gasgets, it is hard to get 100% clean surfaces for $1.98 gasgets that took 2 days to replace.
Yes there are some other very good brands out there but the really good stuff is not carried by most suppliers. All auto shops and even some department stores carry Permatex."
 
...Thanks again Bill
BTW head

...Thanks again Bill
BTW heads are not aluminium.
I will let you know after I replace the gaskets.

Greg
 
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