Cat 7 motors
- Thread starter CJLS123
- Start date
guido4475
Not a Member
If my memory serves me right,isn't a c-7 cat the same as a cat 3126? And, if so, I would stay away from them.I had one, and was one of the fortunate people who had good luck with it, and it is still running with over 800k on it, never opened up.The cat dealer back home in Richfield, Oh told me to adjust the valves every 40k by the same shop, same mechanic, and I will never have a problem, which I never did. But in the meantime,the same people who were telling me it was a waste of my money were dropping valves like crazy, amongst many other things.One guy actually went through 3 of them engines in 6 years.
Deville
Not a Member
I was just talking to my Mechanic about adjusting the Vavles & my overall maintence in my 2000 3126. I too droped a vavle at 385,000 miles. I had only purchased the truck a few months earlier. I was told to adjust them every 100k, OR if I notice my Fuel Economy drop sharply. I was only getting about 8 miles to the gallon, than it jumped up to 10 miles to a gallon after I had the top of the motor done. I average about 9.5 in the summer & sometimes 11 in the winter.
overall I've been very lucky with my small cat, but like the poster before me mentioned I run the same oil every change which is Rotella, I use Lucas, I change all the filters & full grease every PM & I run a fuel additive every re-fueling. I try to change the oil between 7500 & 10k miles.
The thing with the Small CAT's is that they love fresh clean oil. I can always tell when it needs an oil change the motor runs rough.
They aren't bad motors, they just need a little extra TLC.
PM should be a way of life for every trucking company.
overall I've been very lucky with my small cat, but like the poster before me mentioned I run the same oil every change which is Rotella, I use Lucas, I change all the filters & full grease every PM & I run a fuel additive every re-fueling. I try to change the oil between 7500 & 10k miles.
The thing with the Small CAT's is that they love fresh clean oil. I can always tell when it needs an oil change the motor runs rough.
They aren't bad motors, they just need a little extra TLC.
PM should be a way of life for every trucking company.
guido4475
Not a Member
I never dropped a valve in my 3126,fortunately.But if you look at the owners manual for the 3126, it will show maintenance intervals in hours, not miles, including the expected longevity of the engine as well, which was somewhere around 250,000 miles once converted from the hours given in the manual.The Cat dealer in Richfield, Ohio said even though it does sound premature to adjust the valves this often.The reason for this is they have found the valves actually tighten up over time,eventually putting more pressure on the head of the valve, with the end result being in snapping the head of the valve off and it dropping into the engine.When I brought it into them each time, They would show me just how tight they had become while loosening them up to be re-adjusted, which should always be done on a cold engine.They also mentioned that there are some mechanics who do not loosen them up first and then re-tighten them, but to simply put a torque wrench on them and just check the torque.And, you are so correct, the 3126 does love fresh oil,and it does make a difference on how it runs also.Part of this is because a 3126 used the HEUI sytem, which was the injectors being controlled by oil pressure.Right before I sold the truck to my freind, I had it put on the dyno there to make sure everything was ok, and they said the repots showed everything to be perfect at 670,000 miles.I should of kept that truck, but we make mistakes, I guess.
fatboy1
Veteran Expediter
dont know to much about them c9 are better, we had a m2 with it in it servuced at 15000,reg,adjusted valves every 100,000. we use same shop all the time for those maint. it was rated at 335 hp, shop mech said you could rasie it to 400hp.335 was strong enough for us 13000lb in the box and would still pull a 6%grade at 70mph with cruise on. man sure miss that engine
Deville
Not a Member
I never heard of the Vavles tighting, my problem was the exact opposite, they became lose, The mechanic said he could turn the nits of the vavles with his hand, for some reason #6 & #5 seem to have the issue. Right Before I dropped my Vavle I had a Vavle tapping sound that would come & go for about a week, it sounded like a bad Vavle. I've seen them before on big v8's & have gome Thousands of miles with it like that with no issues, Apparently it's a HUGE warning sign if not the last warning sign on a 3126 that BIG poblems aren't too far away.
If you ever hear that sound again bring it in for repairs immediately.
I take it easy on that truck, I don't over load it, although it seems to run better when it has alot of weight on it, I don't rev it about 2000 RPM unless i'm in 5th or 6th gear, unless I need the power. Alot of people knock Lucas, I think Lucas was made for that motor, the added protection in the block, on the pistons, cams & seals are a huge factor.
My 3126 hardly burns any oil, i've gone months without topping it off. These Motors weren't designed for this type of long haul work, Luckly i'm fairly local so i'm not racking up 100 thousand miles a year, they are great as city trucks the motors can haul all day long at low to midrange RPMS lugging fully loaded & won't burn alot of fuel.
Bottom line, like with anything Take care of it & it will last.