Zee

Please help me diagnose this:

Bought my 91 W250 truck about 4 months ago with 126000kms (78292miles), it developed a noticeable knock especially when its cold and it dims down but doesn’t go away when fully warm and it does puff blue smoke on startup and when accelerating and the rpms are almost at the upper limit of 2200rpm (passing vehicles on the highway) The knock is coming from the back of the engine cly #5 0r #6?

I was told that it could be either a rod bearing going bad or an injector not working properly.

When I changed the oil last weekend, I cut the oil filter housing and removed 2 - 2” x 3” areas of paper filter element. I squeezed them in the vice to remove the oil and when I expanded the paper I found metal shavings.

A Cummins rep said that it could be 3 types of metal; Aluminum (Piston gone bad), iron (block being scored) or copper (bad rod bearing).

I removed some of the shavings and tried to see if it was iron and ran a magnet across them and they weren’t attracted by the magnetic force. With that I don’t think it’s a bad block.

The shavings are shiny. Could it be aluminum or the rod bearing material?

After researching online I came across a post that mentions if an injector goes the cylinder runs dryer than it is possible that the piston will burn a hole in the top of it the blue smoke is because it’s sucking up oil from around the rings because it’s not getting enough fuel.

This is my only mode of transportation and things are tight so a new truck is not an option, I would rather repair it to keep the 1st gen going!!!

I changed the coolant last night and it still won’t warm up to normal operating temps. It is starting to get cold up here -15C or (5F), it will eventually plummet to -40C (-40F). Do these engines not warm up in the winter?? Could it be my thermostat? See attached photo of my temp gauge, this is the warmest I could get it after driving on the highway with a cover on the front grill.

Thank you all for your help.

ppiggppenn

That's pretty low for operating temp, but your volts are way low too so I wonder if the gauges are all reading below real value. Is your oil pressure showing above half after warm-up?

Zee

No, the oil pressure is below half (approx 1/8") at idle and creeps up just shy of the half way mark when warm.

My heater is blowing luke warm air at best.

Wettstein

For the warm up problem mine did the same thing. my t-stat was stuck open. For the other problem i think i found an in frame rebiuld kit but i dont recall the site. good luck

Jer12377

I had my ground from my battery to the radiator support break and the gauges read all wrong untill I fixed it. Make sure your GROUNDS from your battery are all good before tearing into the motor. Just my two cents.

schamran

With that, I'd say you have a bad injector. I don't know that much about them, but when I bled my fuel lines last night, I had to bleed each injector, and it seemed to "knock" as I bled each injector. When I had 5 bled, it still knocked. I guess to compare it, a person without a trained ear for diesel engines may or may not have noticed, but I could tell, and bled the 6th injector. Then it smoothed out. It may not give any results, but I think I would start bleeding the injectors one by one. Let a good amount of fuel spray out, and then tighten them. You will notice the sound of the motor change when you loosen one. If loosening one of them doesn't seem to change anything, then you have probably found the problem. Good luck.

And check all of the things that the guys above posted. All valid points.

92smokin blacky

I wouldn't think you need a rebuild already with that low of miles/kms.

I would check your timing first, then your injectors. I would do as Shamran said, Just leave your truck running and break loose the injector lines off the injectors one at a time and it you will hear it miss. Just be sure not to put your fingers or face above the line or they will get sprayed with high pressured diesel. Do that to each one, and if you do that to one, and it doesn't really change the sound, then that one is probably your bad injector.

wannadiesel

Shavings in the oil filter = bad news. I suspect a scuffed piston. Take an oil sample and have an analysis done. High aluminum = hurt piston. High lead/tin/silver/copper = hurt bearing.

ChrisLib

A knock that is louder when cold then gradually lightens as the engine warms is possibly wrist pin related. I have run across this several times over the years (in gasser engines). Perhaps you had/have a dribbly injector putting alot of heat into one cylinder and it scorched a piston?

mprmn08

it sounds like a piston slapping to me. if its louder when its cold and quits down as it warms up, i.e. piston swelling and not as much clearance in the bores. if thats the case typcially an in frame rebuild wont do it. you'll need to have it bored to get your clearances right again. hopefully its just an injector but the fact you had shavings in the filter says otherwise. can you get a pic of the shavings and post them?

TIMMY22

A lift pump on it's way out will tick,tick,tick....

Riflemanusmc

Pull the head and see if a piston and wall is scuffed. Previous owner(owners) got it hot.. Do you have alot of blowby on the dipstick?Or out of the crank case vent and oil filler cap? That will answer you question about a scuffed piston..

Zee

Update 12-04-09:

I changed the thermostat and wow what a big difference. I have heat!!!



Here is a photo of my oil pressure at idle, cruising and accelerating.



I bought a set of new rod bearings and an oil pan seal last night and will drop the pan tonight and see what the scoop is. I bled each injector and it didn't make a difference in the knocking. One thing I noticed on the way to work is that the knocking reduced in sound, perhaps as a result of the engine finally reaching normal operating temperatures?

If I pull the head, will I need a new head gasket when I re-install it?

If a piston and wall is scuffed can this be repaired in my garage or will I have to take it in to a diesel mechanic or machine shop and have it rebuuilt? Any ball park prices on how much this will cost?

I just changed my oil and it is black and I only drove 130kms, can this be from a dirty engine caused by blow by?

"Do you have a lot of blow by on the dipstick?" There is no oil seating from it.

"Or out of the crank case vent and oil filler cap?" The crank case vent is dirty and every now and then it drips oil. Could the accumulation of oil be caused by blow by?

"That will answer you question about a scuffed piston” I’m assuming by contaminating the oil with sut? Can you please explain.

Zee

With regards to overheating...

I wouldn't doubt that they did, it was used for treks across Canada with a camper on the back. Before I changed my coolant I tested it indicated that it was pretty much straight glycol in the cooling system vs. the 50/50 mix. Maybe it was overheated and as a fix they poured straight glycol in the system?? who knows.

NO_SPRK

water cools better then straight coolant. if they where in canada then i bet they ran it rich to keep it from freezing