Mike35r18

Ok well, the alarm is still intermittant, I picked up an OTC professional electrical system tester that is supposed to be able to detect bad voltage regulators, battery cells, etc, it says that the batteries are all good, yet one tested at 750CCA, then 850CCA, when they are 950 CCA batteries. There are 3 batteries, that being the worst. One was about 900, the other 930. So after not finding anything several times, including isolating and testing each battery, I put the tester directly on the alternator which detected "excessive ripple", obviously pointing to a bad alternator, but since I put the charger there is that accurate, or have I messed up the test by placing it so close to the voltage source? I replaced the regulator on the alternator about 4 years ago, was thinking maybe this was a bad connection on a low voltage alarm, which Idk where that is mounted, but am leaning more toward alternator and batteries now, since also finding them low on water last week. Filled them, drove the truck and retested, still throwing the alarm. I guess if there is excessive ripple, and I was overcharging (cooking) the batteries, that would be the explanation for being low on electrolite.

Very good advice about replacing them all and using the other ones elsewhere, and yea the load tester is a carbon pile, and looks to be pretty nice, it is a K Tool International 500 Amp Carbon Pile load tester, should be all I need. And yes mine is a fixed resistance, and it is proving to be pretty worthless. While I have ya here, advice on a code reader for all my heavy trucks in case that malfunction light does come back? Found an OTC that also reads OBDII which I also need, but was really liking the Innova 3150 for that stuff.

I learned something already, and that is my load tester is nowhere near capable of a 500 amp load, however I am looking to purchase one, 100-130 amp seem much more common, is 500 overkill for these batteries or is that the standard for that size? They are 950 CCA batteries, and the 500 amp testers I found test for 15 seconds, and are about $120.

Excellent guys thank you, will try and report the findings, be back later.

Really? Ok, the batteries load tested well while still connected together, but should just isolate each of them (3 total) and test them seperately? What would the max allowable drop from a fully charged battery be? I had contemplated a bad cell (or a couple). Thanks for the fast response!

I have a 2001 RD688S with an E7 400, and am having some electrical issues. There appear to be no signs or symtoms other than the low voltage alarm which may go off for quite a while, then for no explained reason, go off, then come back on again, or just start to rapidly start/stop as if there is a loose connection that is almost making contact after the truck has warmed up and gone for a short test drive. As I went to leave a parking lot after sitting, as I started pulling away the light started going on/off. Then the truck will occasionaly throw an electrical malfunction light, but since I started trying to diagnose this, I have not seen that light, not that I have a code reader for that truck anyways, nor even cruise control, so would there be a way to get that code without cruise? The dissapointing thing is it only has 1200 hours, 17K miles, and is always garaged. What could cause what I believe is a false low voltage alarm? Batteries are 3 years old, load tested well, alternator output is good, battery conditioner is working properly (always plugged in), so I am kind of at a loss at the moment, any ideas? -Mike

Thank you for the welcome, this problem is what prompted me to join, but this site seems like a great resource so far. Anyway, the metal pieces are at the shop right now, but I can certainly take pics as soon as I can get the pieces back. I need to ask the shop if that is the updated turbo, or if it is the original that Mack recommends you replace. I would say that the pices look like they could possibly be part of a washer, but if its of any value the turbo has not made any frightening noises, doesnt smoke and builds boost without issue, the power seems to be there. I wish this was simply a turbo issue, but with that seperate coolant leak, the motor is comming apart anyways, and the shop is contributing our problems to us getting a "bad motor". So we'll be in contact with Mack here shortly. Thank you for your input and I'll try to get some pics on here soon.

I have a 2001 Mack E7 400 RD688S 2500 gallon tanker with an engine problem. The truck only has approximately 15,000 miles, and 1100 hours. Oil changes done every 150 hrs, except for the last one, done at 100 hrs. It is a fire service truck, so it gets run hard from the get-go, but that is the only slightly bad thing for it, although the rest of truck with significantly more time on them never give us a problem. Found metal that looks like a possible retainer clip for something, however according to the repair shop all Jake Brake retainers are intact, although I know that Jake Brake hardware is an update item. The metal was mostly in large pieces stuck to the drain plug, but there is also fine sand sized pieces in the oil pan as well. Oil sample came back with no abnormal wear detected oddly enough, but had a critically high amount of coolant additive present. Which bring me to the next issue... 3 cylinder sleeves were found to be leaking coolant, although no peanut-butter looking oil/coolant mix anywhere. I did have to add a small amount of coolant a couple times over the past year. Did a leakdown test on the cooling system, lost pressure overnight, but they had a difficult time locating where from, it seemed to be small leaks. We do oil samples at every oil change and this is the first abnormal one we've ever had. The shop states the camshaft looks fine. I suggested maybe they are turbo parts which I knew was another update item. The shop has the motor half torn down and have not located the source of the mystery metal. Myself and co-worker (prev. mechanic) thought we heard a rattle in the motor on the passenger side at idle, that would go away and come back. I'm at a loss, looking for ideas/suggestions to try to get this thing fixed and back in service as soon as possible. Thank you for reading this and look forward to your suggestions.