Putting Tow Vehicle Exhaust Underwater?

[PITBoat]

There is no problem with that is there, I mean, the boat's exhaust is underwater, right...?

I have noticed a lag in oil pressure response upon first starting our Suburban in the last month or more, and I'm wondering why. It may well have been doing that for much longer, and I just noticed it.

This is a well-cared for vehicle that I'd expect to go well over 200k miles and it's too early to be seeing serious motor issues, IMO.

Besides pulling the boat since July (and usually putting the exhaust underwater and letting it idle there while I dock), the only other out of the ordinary thing I've done is use an old AC Delco PF25 oil filter at the last oil change in September. I'm not 100% sure that was the correct one, and I changed it for a Fram PH5 not long after I noticed the lagging oil pressure.

Any thoughts?

Our last Suburban ('94 GMC with TBI motor) was into the 220k's and still running Ok when we sold it. And I think it probably had a little rougher life than the one we have now.

 

[MTboatguy]

The exhaust is not a problem at all, been doing it for decades with no ill effects.

How many miles on your rig, you may have a weak main bearing in the lower end that is taking a moment to pressurize correctly and come up to running pressure, what type and weight of oil. Could be the engine needs a good flush or cleaning before you do your next oil change. Oil pressure sending unit could have an obstruction. There are a lot of things that can contribute to what you are describing.

 

[Scott Danforth]

No issue on exhaust

Oil issue could be gauge or bearings or sticking relief valve in pump

Plumb in a mechanical gauge to check oil pressure

 

[David Young]

I would 'never' use a Fram oil filter

 

[Redfred1]

I would 'never' use a Fram oil filter

+ one!!

 

[bigdee]

Oil pressure could just be because temperatures are getting lower. Also most vehicles have dumb gages that get a good/no-good signal from the ECM.....they don't measure oil pressure at all! A idiot light disguised as a gage.

 

[KD4UPL]

I've had 2 different vehicle that had oil pressure gauges showing weird low pressure. In both cases the cause was a faulty sender.
As for oil filters, I'm no expert but I've seen the cut-away demonstrations at the auto parts stores. I will never use a Fram filter. It might actually be the cause of your oil pressure problem.

 

[72fj40]

I think your choice of using the old oil filter design my be the issue. The newer design, AC Delco pf1218, has a anti drain back valve in it. Also, the gm gauges are not very accurate. I was really suprised how bad they were until I installed quality mechanical gauges to run along side my stk gauges.

Im not a Fram fan, either.

 

[PITBoat]

I usually use the Wal Mart Super Tech stuff (including filters), like if I can eat Great Value my cars can too, lol, as long as the SAE quality rating (oil) is at least the latest minimum. I didn't have the filter number with me though and the book didn't go back to '97 is why I went with the Fram. Are they too restrictive, or do they not filter enough? I'd have preferred AC over that if I'd had the right number for it.

Actually what drew my attention to this was the engine actually had some light noise in it on startup once (and it had only been sitting a little while in that case). That has only happened once or twice, including that time, since I've been watching the gauge. The reading behaves what I'd call normal under all other conditions (more pressure when cold, a little less after warm or at idle in gear, etc.).

It acts something like the startup after you do an oil change if you don't pre-fill the filter with oil, only the lag is only 1-2sec and no warning light comes on.

I've never flushed this engine, and we've put nearly 40k of the 170+k that's on it now. I will try that. 10W-30 is the oil weight that I use. I may have put full synthetic in it before, but didn't this last time. It only gets 5-7k miles a year.

 

[bigdee]

Don't let a oil gauge ruin your life. Life was so much simpler when we just had idiot lights, that is why manufacturers are now putting in fake and dumb gauges. Even the gauges that actually read oil pressure (like yours) are dampened and dumbed down so you don't actually see real time fluctuations in pressure.

 

[TyeeMan]

First off I'd loose the Walmart oil and filter. Purchase a well known pure synthetic oil and high quality filter and that will likely fix your problem. Synthetic is a better oil even for engines that don't get run much.

FYI - 5W-30 is the "preferred" oil for your engine. You can use 10W-30 at temps above 0 degrees F but 5W-30 is the preferred oil for all temps.

 

[MTboatguy]

Full synthetic is not always the best recommendation for rigs with over a certain amount of mileage, I run a synthetic blend in my truck and have since I got it over three years ago. There have been credible reports of full synthetics actually causing problems with low oil pressure on higher mileage engines..

For as little as they cost and for as much as they do, get the newer technology oil filters, the Orange Fram filters are not new technology, that design has been around for decades now and does not offer the extra filtering capabilities that new ones do.

Like has been said, it is probably your sending unit that is causing the fluctuation in the reading. Next time you change the oil, get an engine flush run it per directions and then drain oil and change with the band of your choice, but get a better filter.

It will keep ya going longer than you think if you spend just a bit more money on a better product.

 

[TyeeMan]

That could be true, however my personal experience with 5 or 6 vehicles I've owned, all of which I purchased at 100,000 - 120,000 miles I've installed 100% synthetic in them and it has done nothing but make them better. Even going to the extent of reducing oil consumption after the synthetic (and engine flushes) have cleaned up the engine.

My only fail has been with a GM Quad 4 4 cylinder. It must have been pretty sludged up cuz after running an engine flush and running synthetic for a few months it sounded like all the rod big ends were going to come through the block.

My best experience is with our current 08 Suburban that we bought with 124,000 miles, but that's a whole nother conversation.

 

[bigdee]

Please....don't turn this into a oil debate. It could go on forever. Everyone has a preferred brand with no scientific data to support their claim!

 

[JimS123]

Please....don't turn this into a oil debate. It could go on forever. Everyone has a preferred brand with no scientific data to support their claim!

Yeah, right.

So, what about bubbling exhaust under water? Dunno about that, but what if the rear axle goes under water? And what about getting your feet wet and having trouble launching the boat?

Maybe the real question is how to fix the trailer so it launches acceptably. Or, is there a better ramp in the area.

 

[MTboatguy]

If my rear axle goes under water then I have really messed up!

 

[PITBoat]

There are steeper ramps that I'm scared of with a 2WD. This one is the closest to me and is really pretty nice. I have launched/recovered w/o putting the exhaust under, but it seems to go a little better if I can float it (back on, especially). But I was a little concerned about the exhaust thing. The tires (and my feet) are wet too.

The branding thing... I want quality stuff, especially for large investments like my cars and this new boat (new, lol), but I don't want to pay for somebody's name either. Separating fact from fiction then becomes the problem, unless you have time for researching stuff.

I work at a place that puts 4 or 5 different brand labels on essentially the same product. I've seen it done with car parts, food, etc.

Thanks for the thoughts, etc. I'm going to keep an eye on it, then do the flush and that next time. I fired it up in 28F a minute ago, and it wasn't bad.

 

[harringtondav]

This discussion has wandered, as many do. So, back to syn oils. I've used syn engine oils for 23 yrs in six new cars. The last two spec. it. I retired one at 21 yrs/210K mi. My rust bucket '99 Durango is heading the same direction. Both have/had solid engines. Oil consumption was minimal. Maybe a quart top off in a year. I think if you start with syns, the wear will be minimal. Where I live winter salt kills most vehicles.

 

[harringtondav]

Maybe the real question is how to fix the trailer so it launches acceptably.

Yes. That's why I like adjustable bunk trailers. I've got my boat w/in a 1/2" of the keel contacting the cross members. I did this when we bought the boat and were towing with a minivan. My Cherokee rear tires now barely get wet when I launch.

But the boat is so low I have to back the trailer onto 2xs and drop the tongue jack to bottom to pull the out drive. Also zero forgiveness forgetting to trailer up the drive when pulling out. I don't do that one anymore.

 

[Lowlysubaruguy]

I doubt submerging your exhaust in water is causing low oil pressure. Depending on the year of the Suburban ive seen senders failing, instrument clusters failing and worn bearings or oil pump. Pretty wide spectrum right. Senders the easiest way to start id also do an oil change with a quality oil and filter and id run 5/30 which is what anything 2000 or newer specs at. While you can run a thicker oil it was designed to run on this you actually stand a better chance at oil starvation with to thick than thin. If its a gauge issue there are on line rebuilders that will repair and program them to work without seeing a shop with that tooling. If its worn bearings it will need to be tested with a pressure gauge the labor on this is almost the cost of a reman cluster for sure more than having a sender installed.

Now on to submerging your tow vehicle. For those who might have done this. Exhaust isnt an issues. But the rear diff thats another story. You drag a boat on a hot day and back the rear diff deep enough for the vent or any other place that a possible water entry point such as an axle seal which is a couple inches lower than the center of the rear wheels. Hot rear diff hits the water and cools off fast. Any air and theres lots of it contracts requiring the vent which is usually small and often on a rubber hose plugged with dust dirt or some bugs egg sack or its actually below the water line. Water gets drawn into the rear diff and if left long enough oil will float out water will take its place. Water is not a good lubricant and it doesnt play well with gear oil. The cool part is seeing this failure first hand. We had one a long time ago he burned up a couple rear ends. Come in with half the needed oil. What happens is the water boils away and leaves whats left of the gear oil a mess and a bunch of damaged parts. No real evidence of water though. Just a topic I thought id touch on in case it helps prevent someone from landing here.