Interesting running hot question - PeachParts Mercedes-Benz Forum

rg2098 · #1 04-22-2006, 02:05 PM

It seems almost immediately after swapping my injector nozzles out my 300 is running very hot. It has always run at 83 C and never higher then 90 C in stop and go with the A/C. Ever since swapping those nozzles its running at 95 and now 105 C. No overheating, it stays rock steady at 105 now but I am still very concerned. I don't think its a cooling system issue as it was so immediate and jumping the aux. fan does nothing to bring the temps down. Could the new injector nozzles cause this dramatic of a temp change?

pawoSD · #2 04-22-2006, 03:35 PM

Are you sure you didn't damage/disturb the wire running across there for the temp sensor for the gauge? Maybe its just not reading the right temp.

rg2098 · #3 04-22-2006, 05:12 PM

Quote:

Originally Posted by pawoSD

Are you sure you didn't damage/disturb the wire running across there for the temp sensor for the gauge? Maybe its just not reading the right temp.

Its possible the temp sensor went bad, the wire is brand new along with the GP harness. I could be wrong but the engine feels like it is indeed throwing off more heat. I need to borrow one of those IR temp gauges from someone to check for sure.

tram · #4 04-22-2006, 05:15 PM

Your injectors also need a couple hundred miles to "seat".
Actually, disturbing the connection for the gauge sounds like a good theory to me. You may not have been getting an accurate reading before.
To me, WHERE it runs- as long as it is in normal range and holds steady- isn't a huge concern. But, I want that gauge there to tell me if I suddenly have a problem or not- IE, suddenly pegging at hot.

rg2098 · #5 04-22-2006, 09:34 PM

Quote:

Originally Posted by tram

Your injectors also need a couple hundred miles to "seat".
Actually, disturbing the connection for the gauge sounds like a good theory to me. You may not have been getting an accurate reading before.
To me, WHERE it runs- as long as it is in normal range and holds steady- isn't a huge concern. But, I want that gauge there to tell me if I suddenly have a problem or not- IE, suddenly pegging at hot.

I'm pretty convinced that the gauge is accurate. The wire is brand new as of 3 or 4 months ago and it is possible the sensor is going bad but I doubt it. I've spent enough time in the hot engine compartment adjusting the trans bleed valve to get a feeling for operating temp and it feels significantly hotter. It's been driven a couple hundred miles since the injectors were done and it got worse. It started running at 95-100C immediately following the injectors and now its running at 100-105C as of yesterday. I have a back up vehicle for the next week and a half (grandmothers Buick Roadmaster was running hot until I just replaced one of the cooling fans) so I would like to get this under control.

pawoSD · #6 04-22-2006, 09:51 PM

How old is your radiator?

Brian Carlton · #7 04-22-2006, 09:57 PM

Do you notice any difference in driveability?

Meaning, is it more "sluggish". Does it require more fuel to achieve the same acceleration as before the nozzle change?

It's quite the conundrum.........I'll tell you that. There would be no way that I could fathom a nozzle change raising the engine temperature so dramatically, but, if the spray pattern of the new nozzles is off badly.......for some reason........the engine won't make power and will develop significantly higher wasted heat.

Another possibility..........the new nozzles pop at a different point than specified and the timing is retarded beause of this fact.........the driveability should noticeably suffer.

pawoSD · #8 04-22-2006, 10:02 PM

Our '83 has all new Bosio nozzles and the injectors were poptested/balanced by a professional shop, they did a sweet job, you can see how clean they are in these pics:

Temp is the same (always 82C) but it accelerates faster and has noticeably more power....

rg2098 · #9 04-22-2006, 10:25 PM

No driveability differences, although I have seen a bit more smoke now. It fixed about half of my shake at idle. The radiator looks fairly new with out any real bent fins although I don't know when it was replaced. This has been so sudden in the matter of 2 days I find it hard to believe something clogged up.

libbybapa · #10 04-22-2006, 10:42 PM

Injection timing can have a significant affect on the running temp. If the timing is too advanced then the engine can run hot. It can also melt pistons and pre-chambers in that situation.

Because the *actual* timing interval of the injection is a combination of the timing of the pump building pressure and *also* the breaking pressure of the injectors, if you change the breaking pressure of the injector it has a direct affect on the actual timing of the injection interval. If pop pressure is lowered timing is advanced and if it is raised it is retarded as the pump will take longer to build the higher pressure.

Did you check the breaking pressures of the injectors after the nozzles were installed? If not then I would do so for sure, especially because of the running hot situation.

Andrew

Brian Carlton · #11 04-22-2006, 10:46 PM

Quote:

Originally Posted by libbybapa

Because the *actual* timing interval of the injection is a combination of the timing of the pump building pressure and *also* the breaking pressure of the injectors, if you change the breaking pressure of the injector it has a direct affect on the actual timing of the injection interval. If pop pressure is lowered timing is advanced and if it is raised it is retarded as the pump will take longer to build the higher pressure.

Yes, I was thinking along the same line. However, you mentioned a low pop pressure causing advanced timing and additional heat because of this.

This makes very good sense because the driveability would not suffer measurably, but the additional heat would be quite noticeable.

I strongly concur with the need to pull the injectors and have the pop pressures checked and adjusted.

rg2098 · #12 04-22-2006, 10:51 PM

Quote:

Originally Posted by Brian Carlton

Yes, I was thinking along the same line. However, you mentioned a low pop pressure causing advanced timing and additional heat because of this.

This makes very good sense because the driveability would not suffer measurably, but the additional heat would be quite noticeable.

I strongly concur with the need to pull the injectors and have the pop pressures checked and adjusted.

This was my general thought and I wanted some back up opinions. Thats what the forums are for. Anyone know of a shop that will do them? I don't know of any locally and whunter is looking to no avail so far.

pawoSD · #13 04-22-2006, 10:56 PM

There's about 10 or more diesel injection shops here in Grand Rapids, the one we went to completely did all of the injectors for $98 and had it done in less than 7 hours after we dropped them off.

Come on up to GR and use one of our shops!

Brian Carlton · #14 04-22-2006, 10:56 PM

Quote:

Originally Posted by rg2098

This was my general thought and I wanted some back up opinions. Thats what the forums are for. Anyone know of a shop that will do them? I don't know of any locally and whunter is looking to no avail so far.

Roy doesn't know of a local shop to test injectors?