RS Disposal Posted January 21 Share Posted January 21 From what I understand these brass radiators do need to be rodded out occasionally, Which is something I am planning on. But I thought I would tackle the simple things first. In going thru the maintenance history, I don't see where the water filter was last changed. My question is does all the water flow thru the filter or only a portion of it as the systems circulates the coolant? Could a plugged filter be a problem? Going to change that today anyway just so I can log when it was changed. Also bought a thermostat kit That I will hopefully change out later this week, weather cooperating being I work outdoors, just in case I do have a problematic thermostat. The truck runs about 190 all day long in the city. Only gets hot when I climb the canyon, where I do stop and let it cool. Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/ Share on other sites More sharing options...
Straydog954 Posted January 21 Share Posted January 21 I had the same exact problem with my dump truck. Threw a thermostat at it no luck. Took the radiator off and hosed off the fins on both sides and between CAC and that solved the problem. Keep in mind I run on and off road and in dusty environments tho may not be your case but ez to check. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545431 Share on other sites More sharing options...
Straydog954 Posted January 21 Share Posted January 21 Sorry. Took CAC off to get to back of radiator I meant and cleaned everything really good. Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545432 Share on other sites More sharing options...
RS Disposal Posted January 22 Author Share Posted January 22 22 hours ago, Straydog954 said: I had the same exact problem with my dump truck. Threw a thermostat at it no luck. Took the radiator off and hosed off the fins on both sides and between CAC and that solved the problem. Keep in mind I run on and off road and in dusty environments tho may not be your case but ez to check. My truck doesn't have a CAC and have washed off the radiator fins. Was the first thing I thought of. Pretty sure I am going to have to eventually take radiator into the shop. But was just wondering about how much of the coolant actually flowed thu the water filter. I do understand the problems a bad thermostat can cause. Right now just trrying the simple things first one at a time. I'm one that likes to know what fix works and what doesn't work. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545464 Share on other sites More sharing options...
Popular Post Joey Mack Posted January 22 Popular Post Share Posted January 22 the water filter just takes a small sample of water.. I highly doubt the issue is there.. Yes, cleaning/ rodding the radiator can prove well. Another possiblilty is pump cavitation. as you go along on this, I recommend you get the 2 pump gaskets, and pull the pump and inspect the impeller and the housing. When looking at the housing, ( the part that stays mounted to the engine) you are looking for pitting and grooves caused by air in the cooling system.. if you find that, you will need a new housing, cavitation will reduce coolant flow enough to raise engine temp. 3 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545471 Share on other sites More sharing options...
Popular Post JoeH Posted January 23 Popular Post Share Posted January 23 Also what kind of fan clutch do you have? The heat activated type or a fixed fan? If fixed then you're getting all the air flow possible out of the fan, and if heat activated then it is possible the clutch is worn out and not pulling enough air. You should hear the fan roar to life when it kicks on. My 1980 DM686 has no thermostat installed and has a fixed fan. It's just a yard truck now for unloading our cement trailer. Runs at 1700 rpms for about an hour to unload, and the engine temp stays between 150 and 180. Side note on thermostats, I always make sure they have pin hole drilled in them to facilitate purging air out of the system. Hate imagining an air pocket trapped against the thermostat and not getting hot enough to open. 3 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545479 Share on other sites More sharing options...
RS Disposal Posted January 23 Author Share Posted January 23 19 hours ago, JoeH said: Also what kind of fan clutch do you have? The heat activated type or a fixed fan? If fixed then you're getting all the air flow possible out of the fan, and if heat activated then it is possible the clutch is worn out and not pulling enough air. You should hear the fan roar to life when it kicks on. My 1980 DM686 has no thermostat installed and has a fixed fan. It's just a yard truck now for unloading our cement trailer. Runs at 1700 rpms for about an hour to unload, and the engine temp stays between 150 and 180. Side note on thermostats, I always make sure they have pin hole drilled in them to facilitate purging air out of the system. Hate imagining an air pocket trapped against the thermostat and not getting hot enough to open. I do have the heat activated clutch fan. I can hear it roar to life at times but not really when I would think it should be. I have a cab over so I'm right there by the fan. That was one thing on my list of replacing as I troubleshoot the problem. Pretty sure my radiator needs to be rodded, but right now my truck can't be down for that length of time so I just watch my temp really close. Its fine all day long in the valley Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545501 Share on other sites More sharing options...
RS Disposal Posted January 23 Author Share Posted January 23 21 hours ago, Joey Mack said: the water filter just takes a small sample of water.. I highly doubt the issue is there.. Yes, cleaning/ rodding the radiator can prove well. Another possiblilty is pump cavitation. as you go along on this, I recommend you get the 2 pump gaskets, and pull the pump and inspect the impeller and the housing. When looking at the housing, ( the part that stays mounted to the engine) you are looking for pitting and grooves caused by air in the cooling system.. if you find that, you will need a new housing, cavitation will reduce coolant flow enough to raise engine temp. I will definitely look at that when I change out the water pump. Pretty sure the radiator needs rodding out. I'm just trying to understand this engine as I'm sure you are aware of from my "Needing Mack Head" thread Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545503 Share on other sites More sharing options...
Joey Mack Posted January 23 Share Posted January 23 It's All Good Bud... Jojo 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545510 Share on other sites More sharing options...
JoeH Posted January 24 Share Posted January 24 Which cabover model do you have? Just curious what radiator it has. Our MR688 has a monster radiator. Tons of cooling. Probably half again the size of a typical R model, and the same engine. Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545522 Share on other sites More sharing options...
JoeH Posted January 24 Share Posted January 24 (edited) I will add that our DM was overheating running the blower motor for unloading cement. Swapping over to the fixed fan made a world of difference. Old fan clutch was probably worn out. This truck is a good worker for you, I'd swap the fan clutch and see if that helps. Edited January 24 by JoeH Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545523 Share on other sites More sharing options...
RS Disposal Posted January 24 Author Share Posted January 24 13 hours ago, JoeH said: Which cabover model do you have? Just curious what radiator it has. Our MR688 has a monster radiator. Tons of cooling. Probably half again the size of a typical R model, and the same engine. I believe the model is MR685. Dealer lists it as a box truck, but it has a garbage compacter body on it Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545545 Share on other sites More sharing options...
RS Disposal Posted January 24 Author Share Posted January 24 13 hours ago, JoeH said: I will add that our DM was overheating running the blower motor for unloading cement. Swapping over to the fixed fan made a world of difference. Old fan clutch was probably worn out. This truck is a good worker for you, I'd swap the fan clutch and see if that helps. The fan clutch was one thing that is on the list of replacing. Not sure about a fixed fan though being a cab over and the fan just right there next to the seats. Kinda noisy now when the clutch fan does kick in sounding like a jet engine. It's just not kicking in when I would think it should. Thew truck has been a real good worker even though it is an older truck, 1979. Only has about 145,000 road miles on it, most of which are city miles. But engine miles are more from running the pto for the compactor Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545546 Share on other sites More sharing options...
RS Disposal Posted January 24 Author Share Posted January 24 17 hours ago, Joey Mack said: It's All Good Bud... Jojo I want to again thank you for all your insight and help over my journey with the breakdown I had last year. Being a newbie when it came to heavy trk diesel engines, I did learn alot in helping me understand this engine being my goal is to keep the truck in service for a while still. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545547 Share on other sites More sharing options...
Popular Post RS Disposal Posted January 26 Author Popular Post Share Posted January 26 On 1/22/2024 at 3:32 PM, Joey Mack said: the water filter just takes a small sample of water.. I highly doubt the issue is there.. Yes, cleaning/ rodding the radiator can prove well. Another possiblilty is pump cavitation. as you go along on this, I recommend you get the 2 pump gaskets, and pull the pump and inspect the impeller and the housing. When looking at the housing, ( the part that stays mounted to the engine) you are looking for pitting and grooves caused by air in the cooling system.. if you find that, you will need a new housing, cavitation will reduce coolant flow enough to raise engine temp. Changed out the water filter (definitely was totally plugged up) and even though it only takes a sampling of the coolant, being plugged it impeded the flow of the water to a certain extent. The truck now runs about 15-20 degrees cooler in town than before. Still gets hot climbing the canyon though, but it cools down in about half the time. 3 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545638 Share on other sites More sharing options...
Joey Mack Posted January 26 Share Posted January 26 Maybe you relieved an air pocket, and it improved the cooling.. there are Mack engines without coolant filters. Anyway, that's good.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545642 Share on other sites More sharing options...
RS Disposal Posted January 27 Author Share Posted January 27 20 hours ago, Joey Mack said: Maybe you relieved an air pocket, and it improved the cooling.. there are Mack engines without coolant filters. Anyway, that's good.. Are these engines difficult to get all the air out of the cooling system? I know my daughter's jeep is a major pain in the butt to get the air purged out Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545677 Share on other sites More sharing options...
JoeH Posted January 27 Share Posted January 27 I.dpnt think so, but just make sure any thermostat you put in has about a 1/8th inch bleeder hole in it to allow it to burp on initial warmup. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545689 Share on other sites More sharing options...
Popular Post Joey Mack Posted January 27 Popular Post Share Posted January 27 Yes the bleeder is important and must face forward. After a few years of doing these, I just remove the plug on top of the front water manifold, right behind the thermostat housing. then you can pour the coolant in quickly. you can thread the plug back in about 1 turn so you dont make a big mess,, 5 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545690 Share on other sites More sharing options...
RS Disposal Posted January 30 Author Share Posted January 30 On 1/27/2024 at 11:15 AM, JoeH said: I.dpnt think so, but just make sure any thermostat you put in has about a 1/8th inch bleeder hole in it to allow it to burp on initial warmup. the factory thermostat does have a bleed hole that does state either forward or up depending on orientation. the hole is now where near 1/8 th. Should I enlarge this? Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545859 Share on other sites More sharing options...
Joey Mack Posted January 30 Share Posted January 30 No 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545860 Share on other sites More sharing options...
Popular Post Vladislav Posted January 30 Popular Post Share Posted January 30 No, better to not enlarge the hole. It's supposed the air to pass through but also allows some bit of coolant to pass where it's not needed to pass during normal operation of the engine. 3 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-545861 Share on other sites More sharing options...
fernando_say Posted June 9 Share Posted June 9 I had same problem !! And the thermostat have a hole position up or front it, and had air in coolant system, I pull off top screw of water pump to purge air I also clean oil cooler 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73775-1979-mack-e6-engine-cooling-issue/#findComment-553352 Share on other sites More sharing options...
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