4.3L Volvo/Penta runs cold

[johnbo]

Hi, <br /><br />I'm a new boat owner with a 1996 20.5' SeaSwirl, the engine is a 4.3L (GM) 1996 Volvo Penta GL with a OMC outdrive (SX). Don't know a whole lot about the previous history of the boat, seems mostly well taken care of, but there are hints that some problems existed when it was sold. <br /><br />I've taken it out a couple of times. On the first trip, I noticed that the temperature guage never came off the low peg (a bit below 120F). Verified the operation of the gauge (100 ohms = 160F) and the sender (hot water bath). Took the thermostat out and found a collection of chunks of stuff jammed into it.<br /><br />What I found in the thermostat was one piece of torn roundish plastic (might be a water pump vane, don't know). I also found hard light brown rock like pieces about 1/8" by 1/4" squarish piece.<br /><br />I replaced the thermotat. Took the boat out and as I idled away from the dock and into the nowake zones, the temperature came up to 160F and held. As soon as I opened it up, and started running at about 3000 rpm, the temperature fell back to 120F. Temperature stayed that way for the next 3 hours, saw one slow rise to 130 when I was slowed for a bit.<br /><br />The engine starts/run fine. Pulls nicely at speed. Idle seems 'cold' (not too surprising). Gets a little blue smoke smell at idle. No real oil consumption. (I'm assuming that the little bit of oil smell that I'm getting at idle is a cold engine issue).<br /><br />I haven't opened up the thermostat (yet), but I'm guessing that I've got the same problem. <br /><br />When I had the thermostat housing off previously, the interior of the passages had a little surface rust (it had been winterized prior to this), but nothing that looked too bad.<br /><br />The only thing that I can think of is that the previous owner got into some sand/gravel and sucked it into the cooling system. Seems like there ought to be a screen somewhere.<br /><br />The piece of plastic worries me a bit. I've heard that the impellers in the outdrive unit is something that I should do, just as a matter of course. <br /><br />Assuming that the source of the problem is gravel injestion, how would I go about flushing this out of the block? I should mention that when I drained the block, I didn't get anything other than water, other than an initial pulse of rusty colored water. No chunks, sand, etc.<br /><br />Any advice, thoughts, warnings for a new boat owner?<br /><br />Thanks,<br /><br /> johnbo

 

[Reel Poor]

Re: 4.3L Volvo/Penta runs cold

The 160 degree is correct and you are probably right about the pieces of plastic/rubber you found being part of the raw water pump impellor. Its also possible that after ideling out at 160 the t-stat opened and another piece of the old pump lodged in the t-stat not allowing it to operate properly to maintain temp. These pieces can be lodged anywhere between the pump housing all the way through to the exhaust outlet of the risers. Disassembly of hoses and related cooling system componants for visual inspection is about the only way to locate and remove them all.<br /><br />The squarish pieces you found could be rust flakes from inside the block, heads, intake manifold, and t-stst housing.<br /><br />Has the boat been running in salt water? If so it would be a good idea to replace the exhaust manifolds and risers if they are about four years old or older.

 

[Lou C]

Re: 4.3L Volvo/Penta runs cold

I had a similar problem with my 88 OMC this summer. The thermo housings on some models are actually the same. The thermo is held in the housing by a rubber ring that fits in a slot machined in the housing. I'd replace it and see if it stays up to temp. With a properly working thermostat these engines will run at a steady 160. When mine starts running colder like at 120 or so I know the thermo is getting crudded up and sticking and it's time for a new one. The raw water impeller on a Volvo SX is mounted on the engine, not in the drive. If it has not been changed it should be.

 

[johnbo]

Re: 4.3L Volvo/Penta runs cold

Thanks for the feedback. <br /><br />I've replaced the original thermostat (and reseated the O-ring retainer). <br /><br />I've noted the raw water pump on the lower left side of the engine, but I had assumed that there was also a pump in the outdrive unit as well. I had further assumed that the pump in the outdrive was the one that everyone has been suggesting to throw a new impeller kit at. Did I miss-understand that?<br /><br />Is there a safe way to flush or backflush the block to get the remaining chunks out of the block?<br /><br />On the salt water. I have no real way of knowing that part of the boats history. Getting into salt water around here, means dealing with the Pacific Ocean, which is generally anything, but pacific. In an open bow, 20' boat, it would not be my first choice. I'm reasonably sure that this was a lake boat and probably spent the last year moored in the lake, judging by the dirt buildup on slightly hidden parts of the outdrive system.<br /><br />The engine is quite clean and the manifolds and risers look very good. One or two scuff spots or nicks that have a little bit of rust starting. Is there anyway other that disassembling the manifold riser combination to see or judge the condition of that part of the system?<br /><br />Thanks,<br /><br /> johnbo

 

[KM2]

Re: 4.3L Volvo/Penta runs cold

john,<br /><br />had the same problem last summer, sounds so similar I thought I was reading my old post. <br />Anyway with a new thermostat get, things cleaned out of the housing and check the lines to the manifolds too. I had a big piece of rubber stuck in the housing passage that runs to the manifolds that was a pain to get out. <br />I was using a garden hose on the thermostat housing and lines once removed to check for flow.<br /><br />The impeller is easy changed. It's on the lower front of the motor and has two large rubber hoses connected to it. The bolts holding it on are brass so don't over do it on them. Learn from my mistake. And don't forget about the screw that hard to see in the back.

 

[Don S]

Re: 4.3L Volvo/Penta runs cold

John, OMC and Volvo went into a joint venture for a few years before Volvo finally bought them out completely. But for a few years, the SX drive was also called a Cobra. Many people don't realize what you have when you say OMC SX, they just ASSUME you mean the old cobra which had the pump in the drive. That cobra had a dog type clutch and the dreaded ESA shift interrupt system. Your drive has Volvo cone clutch like the older Volvo drives, no ESA sytem. But OMC wanted to keep the Cobra name....... Obviously to confuse people. <br />Once OMC was bought out, The SX name stayed for the single prop, and Cobra went away.<br />Forget the name OMC on your drive. Visit a Volvo dealer for parts, and manuals and you will be in good shape.

 

[johnbo]

Re: 4.3L Volvo/Penta runs cold

Thanks Don,<br /><br />I've been slowly coming to the same realization myself about the name. Any thoughts on how close the Seloc DIY manual for "OMC Stern Drives (1986-96)" are to reality? I have to pick and chose a bit through the descriptions to find the relevant sections. The equivalent Volvo version, didn't seem to cover this unit, but it was hard to tell as the books were shrink wrapped. <br /><br />I'd prefer the factory manual, but I haven't found a good source yet.<br /><br />Tonight is mostly shot already with a late day at work, so I'll pull the raw water pump out tomorrow evening and see what I find or don't find (as in missing pump bits). <br /><br />Any thoughts on how to get the junk out of the water jacket? I'm making some assumptions that because of the relative short time that it took to re-jam the thermostat, that I must have quite a bit more stuff to pull out. I've thought about pulling the drain plugs and seats out and rigging a feed from a garden hose to bubble the stuff out through an open thermostat housing. Not sure how to do this without getting really wet....<br /><br />Thanks,<br /><br /> johnbo

 

[Reel Poor]

Re: 4.3L Volvo/Penta runs cold

Usually these pieces hang up in places where the flow passages change size ie, fittings (where hoses connect), 90* bends, power steering oil cooler, t-stst, manifold to riser joint, riser outlet. <br /><br />Keep im mind, restrictions in a cooling system typically cause overheating problems, and not cold running problems.<br /><br />Your cold running problem is due to no/little restriction (although any pieces of trash/impeller do need to be removed). Water by-passing t-stat some way. I would start there again and see what you find.

 

[johnbo]

Re: 4.3L Volvo/Penta runs cold

I pulled out the raw water pump this evening. Opened it up and found that the impeller is perfect, and not missing any pieces. In fact, it look practically brand new. I decided to leave it be. <br /><br />I pulled off the thermostat housing and found more junk jammed in the sealing surface of the thermostat. Not nearly as big as before. I did find another piece of rubber/plastic in the water below the thermostat. Definitely looks like a piece of an old impeller. I'll put everything back together tomorrow after I pick up another thermostat gasket. <br /><br />Can I use an automotive gasket here? It would seem to be a common size.<br /><br />I'm trying to think of a way to get the rest of the junk out without having to pull the thermostat everytime that I go out.<br /><br />I've heard that its bad to run without a thermostat, but how about a piece of gasket material with a 1/4" hole or so? This would slow down the water velocity, but still (hopefully) allow the junk to eventually make its way out of the system. The pieces that I found today were smaller than a piece of pencil lead (about the same consistancy) so it shouldn't cause a jam in the manifolds/risers, right?<br /><br />I'm also wondering if part of this problem will cure itself this summer once the water temperature comes up. The theory would be that the current 40 something degree water would barely allow the thermostat to open, allowing small bits to jam. Then in the summer with 65-70 degree water, it would open farther and pass more of the debris. Or am I just practicing some wishful thinking?<br /><br />Thanks,<br /><br /> johnbo

 

[Reel Poor]

Re: 4.3L Volvo/Penta runs cold

The paper gasket is the same. <br /><br />There is no real way to get all the little pieces out of the system short of disassembly and cleaning. Even with this there is no guarantee there is not some pieces in the block that you will not see or be able to get out. Time will usually clear most of what may cause a problem. The pieces that do get past the t-stat can lodge in other places that could cause restrictions. I would not recommend running it without the t-stat. This causes uneven cooling, which means there would be hot spots in the engine.

 

[johnbo]

Re: 4.3L Volvo/Penta runs cold

Well, I found the problem, as a prior response mentioned, but I didn't understand well enough at the time. It was a large 3/8 by 1/2 inch chunk of the old impeller that was quite jammed into the bypass passage in the thermostat housing.

Once the passage was cleaned out with a long stiff piece of wire and everything reassembled (for about the 5th time), the engine comes up to temperature nicely and stays there, not matter what speed the engine is at.

The key was noting that the seawater pump is a positive displacement pump and that water that it is pumping has to go somewhere. When the bypass tube was partially blocked (a complete blockage would have cooked the exhaust system), enough water could pass through the port, but when the engine was brought up to speed the pressure was rising until the thermostat open as a function of the pressure against the valve.

Nice to have a theory match reality. I figured this out sitting on a plane going to a meeting. Had to wait for a week to get home and try this out.

Thanks for all of the help.
johnbo

 

[Moku'ula]

Re: 4.3L Volvo/Penta runs cold - MORE ON IMPELLER CHUNKS

Re: 4.3L Volvo/Penta runs cold - MORE ON IMPELLER CHUNKS

Hey Johnbo,

I just bought a 99 Four Winns with the VP 4.3 GLPWTR. The boat looked to be perfectly maintained, BUT the impeller appears to have NEVER been replaced as all but four of the vanes are shreded. Anyway, I will order a new theromstat gasket and open the housing and check for 'chunks'. I'm hoping to recover the pieces in the bypass passage in the thermostat housing as you mentioned...

Any insight as to where this passage is located would be apprecaited. I have the Volvo manual and will take it to bed with me tonight (so much for self-help books or counting sheep), but it sounds like you've been where I'm going.

Thanks in advance for any info.

Jef

 

[johnbo]

Re: 4.3L Volvo/Penta runs cold

You should probably open a new thread. It makes sure that people see your question. However, since I just opened up the page and saw my old post show up.

Basically, the bypass passage is cast into the thermostat housing. But, its not a straight through passage, it has a bit of a dogleg in it. Keep fiddling with it and you'll find an angle that you can see most of the passage.

Please be aware that there are probably other places that these pieces can get hung up in. I'd be worried about the water inlets to the manifolds and the passages into the risers.

Finally, at least on my '96, there were about 8 vanes on the pump. If you've only got 4 stubs left, you may have a lot of pieces to find.

Some of the real experienced folks here will say that finding the impeller in this state is probably symptomatic of the other maintance that has been done or not done. Might be time to look in detail at everything.

Later,

johnbo

 

[Moku'ula]

Re: 4.3L Volvo/Penta runs cold

Four of the vanes are complete. Five are mostly there. Three are pretty much eaten up. I want to start directly upstream from the impeller housing and try to puzzle the impeller back together and removing the thermostat housing looks easy enough for a start.

The service records and condition of the boat indicate it was well cared for - just that whoever was doing the maintenance on the boat forgot the impeller - jeez...

Anyhow - your description is easily understood.

I'll let everyone know how it plays out.

Thanks.

Jef