Where to Add Antifreeze?

[mikedj]

5.0L MPI. There is a threaded brass plug in the top center of the thermostat housing. Is that for adding antifreeze, or do I need to remove the hoses? It appears as though that plug would do all the hoses in one shot. Is that true?

Thanks,
Mike

 

[Great lakes pirate]

I pull the big hose off the housing and pour 4 gallons through after I drain all of the water out.

 

[Lazy Daze]

I pull the big hose off the housing and pour 4 gallons through after I drain all of the water out.

+1, but I do it a little more systematically just to be sure that each section of the engine is covered. I use 2-3 gallons into the big hose (block), then about 1/2 gallon into the intake hose and about 1/2 - 1 gallon into each manifold hose. I fill up the intake hose and each manifold hose twice - just for good measure.

Now, sometimes those hoses get "stuck" onto the t-stat housing nipples and they need a little persuading to get them off. Try twisting/bending them with your hand (you can be pretty rough). Or, use a large slip-joint pliers to twist them free (you'll feel/hear them "cracking" free). Use a rag to protect the rubber. I also have a special tool that looks like a screwdriver bent into the shape of a question mark which allows me to slip it in between the rubber and the nipple and run it around to free the rubber up.

Make sure you are using POLYPROPYLENE GLYCOL AF.

 

[mikedj]

I've always pulled the hoses on my older 5.7L. But this new-to-me 2005 5.0L with the brass plug got me wondering. Plus, there is no sign that the hoses have every been removed, but the plug in question is skinned up as if it's been removed. The same situation exists on a friend's 2006 350 MAG, so I'm wondering if using the hole is a proper procedure. Mercury states clearly that adding antifreeze is required, but nowhere do they say how to do it. My friend used the hole to do his 350 MAG, pouring until it ran out of the stern drive, but it only took about 3-1/2 gallons. My 5.7L usually takes about 5 gallons, hence my hesitation. The bottom line is, I'd like to use the hole, if it's appropriate, but I'd like to know if it's appropriate.

Thanks,
Mike

 

[Lazy Daze]

I have never heard (or read anywhere) that using that plug is a suitable substitute. I don't think you can guarantee that the pink stuff has gotten everywhere. Water (AF) will follow the path of least resistance and just because it's flowing out the outdrive, doesn't mean it's gotten everywhere inside.

My friend used the hole to do his 350 MAG, pouring until it ran out of the stern drive, but it only took about 3-1/2 gallons. My 5.7L usually takes about 5 gallons, hence my hesitation.

I think you are correct to hesitate and that statement there shows why. Stick with going through the hoses.

 

[ZZ13]

I have never heard (or read anywhere) that using that plug is a suitable substitute. I don't think you can guarantee that the pink stuff has gotten everywhere. Water (AF) will follow the path of least resistance and just because it's flowing out the outdrive, doesn't mean it's gotten everywhere inside.



I think you are correct to hesitate and that statement there shows why. Stick with going through the hoses.

Dennis, somewhat related, my 350 Mags have the 3 point drain system with the water distirbution housing splitting the intake into two paths (after it snakes around behind the engine through the steering and fuel coolers). The first path goes to the engine water pump and the second path goes straight up to a "T" which then goes to each riser/elbow (I guess that is the path out for the water when the t-stat is closed and the engine is circulating it to warm up). Which t-stat hose should I hold up higher than the riser/elbow to back up the pink into that path? The big engine block hose or the two smaller manifold hoses? Note: I would be doing this with the boat in the water.

 

[mikedj]

I have never heard (or read anywhere) that using that plug is a suitable substitute. I don't think you can guarantee that the pink stuff has gotten everywhere. Water (AF) will follow the path of least resistance and just because it's flowing out the outdrive, doesn't mean it's gotten everywhere inside.



I think you are correct to hesitate and that statement there shows why. Stick with going through the hoses.

I went ahead and pulled the hoses. Took a little less than 2 gallons before it started coming out of the t-stat housing, but never came out of the exhaust. The hoses that go to the top part of the risers come to the center just below the t-stat and go into a tee, which goes down to the single point drain manifold. The tee hose clamps appear to be non-removable, or at least don't have the typical screws, so it wasn't simple to pull them and fill the risers. So I put all the hoses back on and put my home made funnel extension hose with fitting into the hole in the top center of the t-stat housing. This allowed me to pour from much higher than the risers, allowing plenty of AF to go into the risers and out the back. Still only used about 3 gallons total for the whole engine, which seems short to me, but I'm not sure where else to pour it in.

So, based on my observations and looking at the flow diagram, it appears that the single point fill hole in the top of the t-stat does indeed allow AF into all of the hoses, and adding an extension hose forces it to fill up everything before pushing into the risers.

So, in any event, it's done.

Thanks for all the comments.
Mike

 

[Lazy Daze]

Yes, that is definitely not enough AF to fully protect everything. I just did a V6 about 2 hours ago and used about 4-1/2 gallons.

 

[mikedj]

So what am I missing?

Mike

 

[Lazy Daze]

Bill, I would do your block hose and then the two lower (off the t-stat housing) manifold hoses. That way you're filling the manifolds from the bottom up.

But, I haven't done a boat in the water in a long time and can't really remember how it went..... ie: wondering if water kept coming in due to siphon effect? You may have clamp off the intake hose.

 

[ZZ13]

Bill, I would do your block hose and then the two lower (off the t-stat housing) manifold hoses. That way you're filling the manifolds from the bottom up.

But, I haven't done a boat in the water in a long time and can't really remember how it went..... ie: wondering if water kept coming in due to siphon effect? You may have clamp off the intake hose.

Thanks. I plan to take the intake hose off at the seawater pump and plug it. Then I am going to invent some way to backfill the intake hose out through the bravo III (which will be in the water) and then reconnect it. I will post back whatever my invention is, should it work (ha!). It may be a while. I have a bilge heater and won't drain/fill until it looks like a good hard cold spell is on the way, which doesn't necessarily happen every year in this area.