Temp Spike After Oil Change

[linedoctor]

After changing the oil on my 6BY two days ago, all of a sudden the running temp is way up. Previously, my temp ran about 198. One time last summer it made it to 203 after running hard for a couple of hours on a very hot day but then went right back down to 198.

Now (today) I'm running at about 205-207. At idle I'm running about 201 when it used to run in the mid-180s or so. At one point today my idle temp was 211 for a short time. Crazy. I'm using Mobil 1 full synthetic 5w40, the exact same as I had before. It's hard to believe an oil change could cause this but it was fine before. I already checked for restrictions at the strainer, but it's clear and the intake is unrestricted. I only have 138 hours on the boat and I've never sucked in anything I would think would damage the impeller. Before I call a mechanic, any advice? Could I have bumped a wire/sensor, etc?

 

[walldog]

After changing the oil on my 6BY two days ago, all of a sudden the running temp is way up. Previously, my temp ran about 198. One time last summer it made it to 203 after running hard for a couple of hours on a very hot day but then went right back down to 198.

Now (today) I'm running at about 205-207. At idle I'm running about 201 when it used to run in the mid-180s or so. At one point today my idle temp was 211 for a short time. Crazy. I'm using Mobil 1 full synthetic 5w40, the exact same as I had before. It's hard to believe an oil change could cause this but it was fine before. I already checked for restrictions at the strainer, but it's clear and the intake is unrestricted. I only have 138 hours on the boat and I've never sucked in anything I would think would damage the impeller. Before I call a mechanic, any advice? Could I have bumped a wire/sensor, etc?

201 at idle is higher than normal. I would be rechecking the strainer. Try taking the cover off and opening the through hull to see what kind of flow you get. Don't worry the bilge pump will take care of the water. You do not need to do it long. I have had on the smaller strainers a blockage in the line between the valve and the strainer. It will take a big restriction to cause that much effect on temperature at idle. Restrictions usually show an increase in temperature at higher speeds not lower speeds.

Next slip the cover off the impeller, you may find the problem if you see pieces fall out. Because of the increased idle temperature, it is worth finding the problem. You did not mention the oil pressure, I am assuming that it is normal. If so, that is probably not your problem.

Keep us posted on your checks and progress...good luck.

 

[baz]

Some thoughts for you... sometimes it just takes someone to pester you with questions to think differently. 😉

1)
Are you sure you put the correct amount of oil back in when doing the DIY oil change.

2)
Did you replace the oil filter ?

3)
Did you use the correct oil filter if so and is it tightened down securely with correct torque etc ?

4)
Have you check oil level after these temp readings ?

5)
Any signs of oil leaking in and around the engine and in bilge ?

6)
Collant level OK ?

7)
When was last time you checked oil temp prior to replacing the oil / filter ? If it was several months then the higher temp may have been there before you changed the oil and changing the oil has nothing to do with the high temps you're seeing now.

8)
Did you replace/insert the oil dip stick correctly ?

 

[linedoctor]

Thanks for the ideas…..I had already checked the strainer bowl, removed the top and opened the valve. The water flow was healthy. There are no leaks, and the oil is filled to the max line but not beyond. Actually, all the other points are good. I didn’t check the impeller because the manual says to have an authorized mechanic do it. I’ve never done one before so I’d need a little advice to try it myself without instructions. As far as the last time I checked the temp, we had it out two weeks ago and all was well. The boat is moored in fresh water and happily floated there without incident between the two outings.

 

[trailertrawlerkismet]

Not being familiar with where your Cutwater impeller is located I'll suggest a few things to check on. First get your engine manual out to see of it shows you where it is located. Once you find it you'll either have an inspection/service plate or (hopefully not) a pulley, belt assembly that would need to be removed in order to get to the impeller. If you have never changed out an impeller before and you have the later I'd suggest calling a marine mechanic for a service call. Explain your problem and if the technician replaces the impeller make sure you are at the boat and watch how the mechanic performs the service....ask questions along the way, this way if you decide to change your impeller in the future you've obtained some practical knowledge.

On the other hand if you have an inspection plate you can perform this inspection rather easily. First turn your thru hull engine sea strain to the closed position. Next unscrew the three or four screws that hold the inspection plate onto the impeller housing. Once off get a flashlight to help you see inside the impeller housing. With the impeller left in place visually inspect each impeller vain/fin for cracks, missing pieces, etc. If you find the impeller has been compromised you can try to swap it out yourself or call someone to do the job and (as mentioned above) watch how they perform the task.

Whatever kind of impeller housing you have, if the impeller is found to have broken off pieces take very careful consideration to locating each broken vain/fin that you can. Check inside the impeller housing with your finger to fish out any pieces and or you should read the manual to read what else the engine manufacturer suggest.....there may be a hose that needs to come off for additional inspection. Obviously if you find all of the pieces this is not necessary.

Make sure to open the sea strain back to full flow position when you and or the mechanic is finished.

One additional suggestion, and you may already do this, but always carry a spare impeller for your engine and genset on your boat as you never know when one may be needed and you certainly don't want to get stranded somewhere waiting on a part when you could be back on the water in a couple of hours.....whether you or a technician performs the work.

Please let us know what transpires.

Jim

 

[jroyle]

I had a problem such as this on a previous boat and found it to be there was too much oil added by the "certified" mechanic. He added almost an extra quart and the engine kept overheating. After doing some research I found that even half a quart over the fill line will potentially damage the engine (heat, seals, etc). It turns out with more oil than designed means less heat transfer thru the oil pump and oil filter.

 

[DonGeorge]

Do you have an infrared temperature gun? If so, and you are feeling adventurous it could give you an idea of how hot are some engine parts (oil filters, coolant etc).

This would be much more meaningful if you had a baseline but it could give you a good indication if the engine is actually running hot or if the temperature sensor went on vacation to palm springs.

Jorge

 

[linedoctor]

Thank you all for some very good input and ideas. After exhausting all the easy answers, I assumed it had to be the impeller and cleared the way for the Gallery Marine tech to gain access to the front of my engine. But I was surprised and a little embarrassed to find that the problem was.........

Low coolant. (Very low, as in over a gallon low in a 4 gallon system) An easy fix, and one that Irv from Gallery predicted when I made the appointment. The tech confirmed it in about 2 minutes. The teltail sign? Temp spike at idle.

So you must be asking two questions...first, why didn't I notice the low coolant and second, where did all that coolant go?

Well, I relied on checking the reservoir, which had plenty of coolant in it. But the reservoir level doesn't really mean much as I found out. The source of the leak was a loose clamp at the water heater, which had probably been dripping coolant one drop every few minutes since day one of app. 600 days. The coolant finally went low enough to cause overheating. It was leaking too slowly to be obvious....only the feel of a damp film and the taste of antifreeze under a hose revealved the source. The oil change timing was complete coincidence.

As explained, because the source of the leak was so far from the reservoir, the reservoir did not draw down as the coolant level dropped. Lessons learned:

Pay attention to your reservoir. Make sure the level is changing when it's cold vs hot.

Check your actual coolant level at the fill cap once in awhile.

I hope others will benefit.

 

[abcandjrc]

.......
Well, I relied on checking the reservoir, which had plenty of coolant in it. But the reservoir level doesn't really mean much as I found out. The source of the leak was a loose clamp at the water heater, which had probably been dripping coolant one drop every few minutes since day one of app. 600 days. The coolant finally went low enough to cause overheating. It was leaking too slowly to be obvious....only the feel of a damp film and the taste of antifreeze under a hose revealved the source. The oil change timing was complete coincidence.

As explained, because the source of the leak was so far from the reservoir, the reservoir did not draw down as the coolant level dropped. Lessons learned:

Pay attention to your reservoir. Make sure the level is changing when it's cold vs hot.

Check your actual coolant level at the fill cap once in awhile.

I hope others will benefit.

This is often caused by a loose or defective cap on the coolant system or an air leak between it and the reservoir. The heated water expands and overflows into the reservoir. But when the engine cools, it should be sucked back into the engine. It should work to keep the engine always "full". I am surprised that it would happen but, as you described the situation, perhaps the engine was sucking air back in at the leak rather than sucking coolant in from the reservoir.

Like you say, it is good to check your level at the fill cap. But...... you will introduce air into the system each time, so some recommend against it. Always do it when the engine is cold and that will be insignificant compared to a blown engine. I check it on the first use of any boating day when I check the oil in the engine and transmission and the tension in the belts.