Well Damn:

[1693TA]

Started my water wagon to put it in the shop this evening just as it was getting dark as it's supposed to snow tonight. Truck started right up and I noticed the oil pressure was unusually high. Getting out to get a look under the hood while the engine idled, I heard a faint "pop" and seen engine oil streaming out from underneath the truck. Jumping back into the cab and yanking the kill cable the engine promptly shuts down. I get to looking and the oil cooler has blown it's seals at the inlet flange and had been spraying oil several directions. Don't know why that would have happened but I'll need to pull the oil cooler for rebuild and see if the oil pressure relief valve has stuck closed. The oil cooler is simply a bunch of tubes which the oil passes through and they are surrounded by engine coolant. I would think the oil pressure relief valve should have relieved prior to blowing a seal out. If the pressure gauge reading were not noticed high, I'd simply think the seals just went from age. The oil is Delvac 15W-40 and the oil pressure was normal last run of the truck. Don't know why the oil would have dead headed causing elevated pressure as it's not really cold out yet?

Oh well, it'll give me something to do.....

 

[Ronsii]

That's a bummer hopefully it's something simple....

 

[1693TA]

Thanks. I have an air fitting and ball valve plumbed into the wet tank so will charge it up via shop air, release the brakes and drag it into the shop with the skid steer or lowboy tractor with winch. Not a big job to rebuild the cooler but getting it off the engine in this series of truck is really "tight" as the cooler is almost recessed into the frame rail on the left side. Reach is very difficult to get to fasteners. Think I even have the seals on hand. Last one of these I had to do the "kit" was supplied with five sets of everything and I think I know where the package(s) are.....

 

[DIYDAVE]

Coupla years ago I hadda dodge V10, started reading high, looked at the sending unit, and it were swelled up, looked like a sausage! R&R'd the SU, and it read normal. Don't know if this'll help ya, or not, But you made me remember it...

 

[1693TA]

Was "bugging" me so ran back out to the shop to look in cabinets for the rebuild kits. Not only did I find the kits, I also found a cooler for each an inline six, (ENDT/E6 series) and a V8 engine already rebuilt and in the cabinet. One of my former employees must have done them for me as I don't remember? I've had several of these engines as runners and for parts over the years so anything is possible.

Of course let's not forget I am over 50 and memory is fading.....

 

[1693TA]

Coupla years ago I hadda dodge V10, started reading high, looked at the sending unit, and it were swelled up, looked like a sausage! R&R'd the SU, and it read normal. Don't know if this'll help ya, or not, But you made me remember it...

Thanks, my Dodge is a V10 also and did the same thing a few years ago. Replacement sending unit has been fine since.
This Mack reading is from a direct reading pressure line so I tend to believe it. I'll try to get the cooler removed this week but I don't use the truck in the winter so not a real high priority except I do like it kept inside during the cold months.

 

[Ronsii]

Still kinda weird though.... I think the blowout is a symptom not a cause unfortunately...

 

[RZucker]

I know very little about Mack engines, but does that one have a pressure relief/bypass valve for the oil cooler element?

 

[1693TA]

Still kinda weird though.... I think the blowout is a symptom not a cause unfortunately...

I agree. The oil cooler unit's seal to the block was probably the weak link in the chain. The oil is quite thick and I'm thinking restriction through the cooler was great enough with cold oil the back pressure overcome a weak O ring seal. That is the way these things seal to the block in the oil path. I've seen that oil pressure run high in the past as do two other Mack V8 engines I have but it comes back down after just a few seconds. This one did not. The engine only ran about 30 seconds before I got out of the cab and less than a minute before I seen the oil running. I stuck my fingers in the pool an it's quite cold, and thick.

The oil pressure relief valve is a bolt on affair external to the pump but on the inside of the block. The pan has to come down for access. Through years of collecting I have a set of spare bearings in std size for the engine and if'n I drop the pan I'll "plastigauge" the bearings as I have no history. Oil pressure in this engine typically is about 30 psi at low idle when warm however and about 65+ upon cold start.

Other than the odd firing order of this series of engine there are no unusual noises.

Thanks,

 

[1693TA]

I know very little about Mack engines, but does that one have a pressure relief/bypass valve for the oil cooler element?

Not for the oil cooler itself. There is the main pressure relief valve internal to the block, then the relief valve for the oil filters. However, the tubes the oil flows through are quite small individually, (there are many) so a bit of restriction there and the cold oil may be a contributor. Would be a dead giveaway to problem area if the oil pressure gauge port is just prior to the cooler element but I cannot remember where it is on this series of engine. The service manual does not actually show the sample point.

 

[fast_st]

I think the truck wants to move to southern florida

 

[1693TA]

I think the truck wants to move to southern florida

So does it's owner. I installed, then upgraded the radar at West Palm Beach and really liked the area. Actually met Michael Jordan there too as he was walking across the ramp to his aircraft.

 

[grandpa]

Well, on the bright side, your oil pump seems to be strong!!!

 

[1693TA]

Think I've located the problem and looks to be an easy repair, but do need to remove the cooler from the engine. Apparently, (prior to my ownership) the cooler pack was rebuilt and when reinstalled, the bolts that go through the bottom flange into the side of the block were not tightened properly. Both could be rotated easily with a 1/2" open/box wrench. This is in the direct discharge flow path for engine oil from the pump to the cooler inlet and sealed with a silicone O ring which probably let go from squeeze out.

I'll drag the truck into the shop later in the week and address it. We got a couple inches of snow and the temperatures are to nosedive tonight.

With me being old, decrepit, feeble, and just a touch of senility, I'm thinking it can wait a few days.

 

[Ronsii]

We'll remind you if your senility get the best of ya'

 

[1693TA]

Got to digging into the cabinet and found the seal and gasket kits for the oil cooler assembly's. As mentioned earlier they came in packs of five each and the packages still have four each in each package so quantity reconcile.

Although the "spare" oil cooler in the cabinet has an "R" painted on the case, (my code for rebuilt) I cannot remember doing it myself. I'll break it apart to ascertain status as really don't want to do this again. The weather forecast appears to be warming a bit so maybe I can drag the truck into the shop later in the week.