Logo
FULL SITE MENU

Where is the antifreeze going ?

M

mike33egg

Member
Port engine, no apparent overheating prior to riser/elbow changeout, probems with overheating post change.

Engine is 318, fresh water cooled, previously asked about fill levels in Sendure heat exchanger. Bought boat with no maintenance records, assumed that due to age, risers and elbows needed replacement, which was confirmed after removal.

Episode began after utilizing a infrared heat thermometer. Imbalance in temps side to side, which eventually coincided with blocked elbow disovered during replacement. Used OSCO replacements, with open gasket, which is to say, open exhaust port, and open port <top of gasket> for raw water flow.

Engine started after replacement, began to overheat, shut down, poured an additional gallon of antifreeze into heat exchanger after "burping" per Fast Jeff. All appeared fine unti tonight, restarted engine, was fine at idle, advanced throttle to 2500 RPM, engine began to overheat, approx 200 degrees, verfified with infrared on both logs. Shut down, added 2 gallons of antifreeze, which seemed excessive. No antifreez in pan under engine, nothing on the engine oil dipstick. Checked exhast, no visible sheen. Restarted engine, still overheating at around 200 degrees.

Never checked raw water impeller or thermostat prior to riser/elbow replacment, if possible can someone point me in the right direction before I dismantle the engine plumging system ?
 
I suspect you are loosing coolant into the exhaust system at the manifold/ riser joint. There should be both a gasket AND a substantial plate there to prevent that from happening.

Jeff
 
Jeff, thanks for the response, that is exactly what's going on. Have been dumping gallons of antifreeze into the port heat exchanger, and watch it steam out the exhaust pipe. There is only a gasket between the end of the log, and the new riser. No one had previously mentioned the need for a plate ? Would that then take a gasket, plate, then another gasket to the riser ? Neither engine had a plate at that joint, only gaskets, and I haven't seen any as replacement parts for this set of manifolds and risers.
Can you point me in the right direction, I'd certainly appreciate it !
 
You need a plate and two gaskets--one per side. Not sure where to buy them, sorry. (I have RWCooling.)

Jeff
 
Are your manifolds fresh water cooled? If the manifolds are raw water cooled wouldn’t there have to be a leak in the heat exchanger for the coolant to mix with raw water and exit the exhaust? Jeff I can’t find the plates you are talking about in the Osco catalog, are they not supplied from Osco? I'm just curios because I did the same job and did not use a plate between the 90 degree elbow and the manifold.

Matt
 

Attachments

  • osco-pg22-25.pdf
    157.8 KB · Views: 170
Last edited:
Item #19.... on some setups, instead of a special gasket, a blocking plate and two regular gaskets are used. Note difference between #17 and #19..
 
I used item 17 the gasket with the hole for the raw water and did not use a plate. So I guess that Mike must have freshwater cooled manifolds if he is loosing coolant at that location.
 
If you get desparate, a good machine shop can fabricate that plate out of 1/16 inch stainless. I just made something similar out of titantium.

Jeff
 
Should work if used with the blocking plate. I have FWC and those gaskets work because the top hole in my elbow doesn't go anywhere.

Eero
 
Update, well I can honestly say that a) I can't find a referenced plate, b) retried a new gasket, no change, still steaming away. This is the 3rd time I've had it apart now, and I just can't get a grip on it. Anyway, I guess I'll tear it back down tonight. I'm considering a gasket sandwich but I'm concerned about the ability of the bolts to compress it once I've reduced the bite. I found 3 old gaskets, and may try them next, but I'd sure like it to be for the last time. I'm getting no where fast.

One thing I don't understand is the gasket application, which is to say, use open or closed. Closed = no hole at the top, Open = hole on top. The starboard engine had Closed installed at the end of the logs where they meet the riser, I replaced them with open, but that engine doesn't steam, so it sealed correctly. Item #19 on the Osco part list appears to be a gasket, not a plate, is that correct ? Both engines are fresh water cooled, with a Sendure heat exchanger, and external plumbing on both logs to allow antifreeze to cycle through the manifolds, at least I think that's whats going on.
 
Last edited:
In a raw water cooled engine, raw water flows thru the exhaust manifold and then exits the engine via a passage to the exhaust elbow and thence overboard.

On a "full" FWC engine, antifreeze cycles thru the exhaust manifold and back to the block and Heat Exchanger and is prevented from exiting thru the exhaust elbow by either a blocking plate and 2 regular gaskets (#17) or a gasket with the water passage blocked (#19).

Re: #19. This is the gasket to be used in a full FWC system if a blocking plate isn't used.

I suspect that the blocking plate was used by aftermarket manufacturers who found that it was cheaper to tool up for a metal plate and use two regular gaskets, than to tool up for a special gasket. It's cheap to tool up to punch metal plate as almost any corner machine shop or sheet metal shop can do it. Tooling up for a new gasket is another story.
 
eero_karppa said:
Should work if used with the blocking plate. I have FWC and those gaskets work because the top hole in my elbow doesn't go anywhere.

Eero
Click to expand...

Ha, solved that mystery. The reason the hole doesn't go anywhere is because there was a 1/8 inch thick gasket with no hole that looks like metal but is actually some kind of fiberous material. This gasket was stuck to the elbow mating surface (didn't notice it before) and after prying it off there was a coolant passage behind it. The other end of the manifold uses a gasket with a hole to allow the coolant to exit to heat exchanger.

Mike, if your elbow/manifold joint sealed properly you might already have the gasket with no hole stuck to your part and that's why the gasket with the hole worked. If not then the gasket you used should be pouring your coolant out the exhaust.

Eero
 
Last edited:
Eero, Thanks for your suggestion, I understand how that gasket can be missed. But let me tell you what I've done during this episode of riser and elbow replacement. The engines are both full FWC installations, which to me means, there is antifreeze in the jacketed portion of the exhaust logs. They have all been reassembled with OPEN gaskets. Now, if I understand the closed flow, the open hole at the top of the gasket is not flowing antifreeze, maybe raw water, but does it pass through the log itself, or only at the riser where the raw water hose is attached from the heat exchanger ? The only piece I'm having problems with seems to be the connection from the port engine, outboard log to riser. I pulled that joint apart, and antifreeze and water poured through the gasket. I used one of OSCO's green gaskets, no sealant as recommended. I re-cleaned both riser and log surfaces to ensure they were clean, then reassembled using another green gasket. It didn't seal again. The inboard log to riser connection was good during the tear down, so I'm concentrating on the outboard coupling.

I intend to use an old style black gasket with permatex on the next go around to see if that'll do the trick. The one question that I can't seem to answer however is this, what flows through the top portion of the log where the open part of the gasket seals or is blocked. In my mind, only antifreeze is in the log jackets, not raw water, that is injected at the riser only from the heat exchanger. Also too, since I used open gaskets on all connections, to include the starboard motor, why wouldn't that engine be losing antifreeze as well ? I doubt that I'm making myself clear, I'm confused myself with the gasket application for this setup. If I'm supposed to use a closed gasket on the aft end of the log connection to the riser and an open gasket on the forward end of the log to allow the antifreeze to be circulated back into the block, what is the open or top hole aft actually flowing ??
 
replace all 4 aft end log/riser and riser/elbow gaskets with the blocked kind. There should be only antifreeze in the logs in a FWC system and it would flow out the top hole if not blocked. RWC system seawater would exit out that hole from the log.

I'm in the process of putting mine back together and this is my first inboard so I hope my information is accurate.

Eero
 
Eero, I agree with your assessment based on what I think I know. However, I'm not losing antifreeze or steaming from the starboard motor with the open gaskets at the log to riser interface. I'm mystified at this point, there is something I still do not understand about the flow, and isolation of antifreeze from raw water. I should be losing antifreeze at a high rate with the open gaskets, but I'm not. Something else is amiss, and short of tearing down everything and verifying gasket types and placement, I'm at a loss as how to proceed.

Amazing how you can attempt to correct a problem, the create more in the process. Neither motor was losing antifreeze or overheating before I changed the risers and elbow. The starboard motor had the blocked gaskets, the port did not. How is this possible without some kind of noticeable impact to antifreeze levels.

<sigh> maybe I'll call OSCO, but I'm certain they'll tell me that I need the blocking gasket on the aft connection from log to riser. It won't explain the condition I described above though.
 
Verify if in fact your system is plumbed for full FWC. If it is, you always require two gaskets sandwiching a block off plate. Forget about the small hole aft end of the gasket, the block off plate has no hole and as such will seal. If for some unknown reason your other motor is not leaking consider yourself lucky, pull it apart and install the correct parts before it starts to leak.
 
Gents, had a conversation with Jerry at OSCO Motors, great guy. He confirmed that I need the blocking gasket at the aft end of the manifold where it connects to the riser. I specifically asked about a blocking plate, he said he's not aware that OSCO ever provided one for this application, only for a Mercruiser application. I guess I could have one fabricated. At any rate, it's time to tear them all down again and start over. Jerry is sending me new gaskets since I indicated I was having trouble getting them to seal. Thanks for everyone's input, I'm glad that the gasket placement issue is confirmed, even though I'm not understanding why I'm not losing antifreeze from starboard motor. I'll keep posting updates as things unfold.
 
Update, tore down all riser to manifolds, installed new blocking gaskets, starboard motor appears fine, no antifreeze loss, no steaming, steady temps across logs and thermostat housing. Port motor steaming, but no apparent loss of antifreeze this time. So, my new question is this, I now suspect a bad casting on the riser, it's the only place I can posssibly figure that water is entering into the exhaust. Is there a simple way, short of replacing parts that I can tell which side is the culprit ? I could attempt to temporarily disconnect the raw water discharge hose from each individually, but I'd probably burn up the exhaust hose. Anyone know of any other tricks ? Again, thanks in advance, this has been a seriously trying experience thus far, but I'm learning alot.
 
..."Is there a simple way, short of replacing parts that I can tell which side is the culprit "

Sure, and you should have been doing this from the beginning: Shoot the entire exhaust system with an infrared temp gun to find your hot spots.

Jeff
 
Ok, as I suspected once again, the port log to riser connection once again did not seal. I don't get it, that's at least the 3 time that connection failed. I had brand new gaskets from Osco. I guess it's either time to replace the log, or I'll permatex the gasket in place. I'd rather not pull that side due to the clearance issues.
 
Don't get pissed at me, but you might be installing it wrong. The weight (ugh!) of the riser/ elbow pulls down on the joint like crazy, pinching the gasket more at the bottom than at the top.

When I install them, I snug the top bolts FIRST, then the lower ones, then I tighten the top bolts before the lower ones. You might try that. Also, the gasket surfaces must be absolutely clean!

Jeff

PS: Do you have those dopey sweivel elbows? If so, they love to leak! I have a sure fire cure, however.
 
Jeff, no swivels on this unit, thank GOD, even still, this thing has been a bear, and it persists. Surfaces cleaned, razor bladed, wiped with acetone, using the new Osco GREEN gaskets with a heat activated bonding agent on them to seal to the surface. When they seal, they're sealed, but this joint never seals as if it never got hot enough to activate the bonding agent on the gasket.

I understand about the pinching arrangement, and have tried the same steps you identified at least twice. The other risers sealed fine, just this one that won't, at least not yet anyway. I'm breaking out the permatex this time, I'm getting weary of doing this repeatedly over and over again.
 
if they are in good shape, take them to a machine shop, have them clean up the mating surfaces, sounds like one face or the other is a little off
 
Ok, I surrender, off with the log. I used permatex on Friday in an attempt to seal that joint. Looks like I slowed it down, but did not seal it. I was finally able to get a decent look at the end of the log, and the jacketed areas looks deteriorated, with not alot of surface area to create a good seal. So, off it comes, maybe that'll do the trick. Unfortunately, I now have to be a contortionist to reach the manifold bolts themselves, or do it by feel only, and pray I don't break anything in the process. I'll start the PB blaster routine tonight, and drain the manifold before attempting to loosen anything obviously. Of course now I have another problem with the starboard engine, new post on that issue which is different from this situation.
 
Back
Top