what is this knocking sound?

[Bobbo's F-350]

I have a 1993 F-350 with a 7.3 idi and I love it. But just a little while ago. I blew a head gasket on it. So anyways I fixed it. You know all the stuff you have to go through, timing, torqe specs and all that fun stuff. Anyways I did everything I had to do. Timed it right on, everything is torqed to spec. But when I fire it up, when the motor is cold. It has this knocking noise and I can not figure it out. It funs perfect, no power loss and the noise kinda goes away after it warms up. I dont get it.

 

[Diesel JD]

Well if it goes away when its warmed up, then its probably just the cold timing advance. The correct timing which you say you have is 8.5*BTDC so 2-3 more degrees means 10-11*BTDC, its gonna make some noise.

 

[BigRigTech]

I agree with JD, mine has that "sharp" rattle too until the cold advance kicks off.

 

[Russ]

If it sounds like a Knock (kind of like a rod knock) it sounds like an injector poping off too early.

 

[Full Monte]

I think it could be something else. If one of your injectors is ******* a solid stream of fuel into the cylinder, it will create a big knock when the piston tries to compress the liquid fuel. I've had this happen. Thought it was an glow-plug tip that came off and was rattling around in the cylinder. That happens sometimes too. It's best to have your injectors tested first so you can eliminate that as a variable.

 

[Bobbo's F-350]

well thanks for the info. I am glad its not a rod knocking or anything.

 

[RKOCH]

Testing injector is horse crap and a waste a money. The shops around here charge 25 to 30 bucks to test an injector. I can can buy remans all day for 25 bucks @ the international dealer. If am going to pull that injector and it is going to cost the same money to test one as it is to replace it you might as well replace it.

 

[RLDSL]

Testing injector is horse crap and a waste a money. The shops around here charge 25 to 30 bucks to test an injector. I can can buy remans all day for 25 bucks @ the international dealer. If am going to pull that injector and it is going to cost the same money to test one as it is to replace it you might as well replace it.

That all depends on the injection shops in the vacinity. The injection shop here doesn't charge anything to test them, They only charge if they have to rebuild them. About 80% of the time I get out of there without going broke ... the other 20% of the time I make up for it, but they're good guys. They've always been straight with me.

 

[RKOCH]

No one test for free around here @ all! $25 is the going rate per injector no freebies around here. The want to charge $200 to test 8 injectors. Just bought 8 BB code injectors for $205.

 

[suv7734]

Testing injector is horse crap and a waste a money. The shops around here charge 25 to 30 bucks to test an injector. I can can buy remans all day for 25 bucks @ the international dealer. If am going to pull that injector and it is going to cost the same money to test one as it is to replace it you might as well replace it.

IMHO you should look for a different injector shop. I generally have them (all 8) done for free or about $25.00 if I'm in a hurry and want them right now.
The problem with just installing new or reman pieces is that they need to be tested before installation as well since it's not uncommon to get a bad one 'out of the box'.

 

[RKOCH]

I have installed hunderds of Navistar remans and have never and I mean never had one bad out of the box in 18 years. There is no shop @ all within aleast 100 miles of here that does not charge the same thing to test injectors. That just seems to be the going rate for their time I guess.

 

[Diesel JD]

Some people are better than others at building these injectors, maybe the person or factory that builds these is superior. I too have had good luck with new or reman injectors being good. For $200 a set you are right it is no way I would test them, you'll wind up throwing good money after bad. Around here, one shop I have used charges $32 for a set the other is free, and I haven't checked with IH. Guess I am lucky.

 

[RKOCH]

If some one here would test them for for that kind of money sure. But just can't see paying them $25 a peice to test to tell me they are bad and then pay $25 a peice to replace them. If you can get them tested for $25 to $32 a set go for it, it just ain't happing in these parts.

 

[Diesel JD]

That sucks, even the shop that charged me let me apply that price towards a new set, and he let me watch so I could see they were bad and he wasn't just BS'ing me to sell me new ones. It would be nice to have a tester like Agenem, but they probably ain't cheap, I tell ya.

 

[Bobbo's F-350]

I was also wandering, My A/C compressor just took a crap. Would I get any noticeable horsepower change if I replaced it with a bypass pullie.