Blackened

We purchased a Sterling at a Mack dealer and they had no problem changing some of the settings like the speed governor.

The EGR cooler has been confirmed cracked internally. Its good that its not a head gasket, but sucks that it costs $1500! Even the Mack parts dealer was shocked at the cost of these things. I tried to see if he could work out a lower price since we been dealing with them for almost 35 years now and he said that price is the best he can do. I'll have the part on Monday and installed some point during the week. The Mack service manager said that they are releasing a updated computer tune in the very near future that's supposed to prevent this from happening again. He has a tractor with the same exact problems in his shop this very moment and they are waiting for the update to try out on it. I didn't get all the details, but they told us to bring the tractor by when its available. Ill be sure to find out what exactly it does to prevent this problem. Thanks for the info gentlemen, I'm hoping this ends my headache!

Thank you sir. I knew there had to be some sort of tool to perform this. Im also glad to hear that the head gasket is the least likely issue for this problem.

Sorry to dig up a older thread but, Would excessive soot in the cooler cause it to crack? Im having this coolant pressure problem and I'm leaning towards all the crap that's built up in the cooler building up pressure and put a crack into the case which is now pressurizing the coolant.

This is my next step. I replaced the waterpump and even pulled it back out to check to be sure it wasn't slipping on the shaft. I took the truck to Albany the other day and it blew coolant out the overflow tube once again even with the one piece tank. I bled the air out and filled the tank again and it got me home without any issue. The next day I took it upstate NY with a load and it pumped coolant out again. I bled the air and refilled it, but it blew out again in a short while. I checked the coolant its a tinge darker and has a slight exhaust smell to it. I called Mack and the service manager told me that they been changing the EGR coolers for these issues. Then he quoted me a price of $1500 for it! I pulled it off the engine this afternoon, but a little unsure what the best way to test it would be. I didn't see any coolant in the exhaust inlet or outlet, but it probably burned off anyways so how exactly can I test this before I throw more money at it without being 100% sure? Thanks for any info. For those keeping score.... Replaced and then re-checked waterpump. (No issues) Replaced both thermostats. Pulled out radiator and checked for blockage. (Nothing inside, no blockage) Checked oil cooler filter (Clean and clear) Replaced the 2 piece reservoir with the updated one piece (Didn't solve issue) Flushed coolant twice Replaced water filter twice No oil in coolant No coolant in oil No smoke Let air compressor pump but didn't replicate problem. Now I pulled the EGR cooler off and plan to test it to be 100% sure. There was a hand engraved etching on the back with the date 12/Nov/2003 and Made in Mexico. I have 298K miles on the truck and this is the original cooler so its very possible that this may be the issue. Now how do I test it???

Happy to announce that the truck has been trouble free so far and I've been running the hell out of it with a drop of coolant loss. Thanks again guys for your help! I would have never figured a TSB for a problem that has no actual reason behind it.

Simple test would be to remove the throttle linkage and work the pump by hand to be certain if its in the pump or the linkage. I have had linkages bind near the exhaust on several occasions.

LOL Ain't happening. Going through there with a day cab and a 48'er is enough of a pain.

I thought air compressor at first as well. I had a Cummins in a sterling that had a bad compressor head gasket and it pumped air into the coolant. You would smell coolant in the air tanks and it would be warm air coming out the lines. I opened the tanks on the Mack and let the compressor continue to pump, but I couldn't replicate the problem. Also any water that built up in the air tanks was clean and ice cold no matter what the temp the engine was so that made me look elsewhere for the issue. I ran it hard on the NJ turnpike for 10 miles and it didn't build pressure like before. I also routed the overflow tube where I can see it without opening the hood each time I came to a stop. So far no issues, but if it does start to pump up again, I plan on pulling the EGR off the engine and give it a full inspection. One odd thing I noticed, When the waterpump let go I replaced the pump along with a new Fleetguard water filter. Not soon after the swap I started having issues. When I pulled out the oil cooler filter I saw little grains of the element that's inside of the water filter in the screen. Normally they shouldn't escape the filter and get into the coolant. At least I've never seen that before on any engine's cooling system I've worked on. After replacing the double tank with the single tank, I also replaced the water filter again as a safe guard along with new coolant. Now I'm wondering if a defective water filter was the cause of my problems to begin with. I tried filling up the filter I took off the engine with water along side a brand new water filter and it seems to fill up slower then the new filter, I filled the middle and it don't go down and fill the outer passage of the filter as fast as the new one so it's making me suspect that it was building pressure due to the blockage inside the filter. Bad filters are very uncommon so I'm just curious if I won the unlucky lotto in this situation. Anyone ever experience a defective filter before?

Its basically like driving a full size bus with a trailer on the back. I'd like to see what route he took to get through NYC with something like that.

Well today was the first day out with the new tank setup. I have 2 runs from the Trade center to NJ and I been pushing it as hard as I can to see if its really fixed, so far so good. The temp gauge has been doing its normal up and down sweeps as well as the oil temp. Nothing blowing out the overflow line and the temp also comes down after idling for a while unlike it did the last time. I would have to really put some long distance miles on it like I did when it was blowing out the last time to really prove its fixed, but so far its back in service. Thanks for all your help gentlemen with the TSB info. I probably would have ended up tearing this thing down only to have the same issue after all that labor.

A bolt sitting in the block for 50yrs sounds like a nightmare bound to happen if it snaps off. You may wanna order the plug and move on with life. I would hate to have something that seems simple enough turn into a huge project.

Just a update... I ordered the one piece tank from Mack yesterday and today and they sent me the wrong part. The parts guy cross-referenced the tank part number on the TSB and came up with the number of the part he sent me which was just the top half metal tank. Thanks to you guys, I faxed him over the TSB showing the tank and Ill have the right tank on Friday morning. Crazy thing was that the top metal half of the tank at my cost was $370, the one piece metal tank was around $295. You would think half a tank would be cheaper! Im just wondering that after running almost 290K miles with the split tank set-up, why would it all of a sudden start to build pressure? Im wondering if higher mileage plays a part in this or just a design flaw that shows its ugly head at any given time? Ill have it installed on Friday then run the hell out of it and see what it does. Next step after this is to tear it down.

They said that the "R" model was the most popular Mack with over 400K units sold. I think that number is pretty low considering how long the design has been around.

We had a Superliner day cab with a Silver 92 in it. It was originally built to pull a dump trailer. After rebuilding the engine twice and having a driver come back with a 90mph speeding ticket, a for sale sign was put on it. This has to be almost 20yrs ago since we sold it.