So the previous owner of our coach drained the cooling system and inspected the radiators (which are in near perfect condition) but as you know, you can't prevent air pockets when filling back up unless you pull a vacuum which he didn't. So my coach is overheating and I can't get anywhere very fast. I've tried to let it sit to burp the system and add more coolant/distilled water but I only got about 2 gallons in. The purge tube (the little plastic one that dumps near the bottom of the curbside engine access door) keeps puking coolant. So I can't seem to get ahead on the air purging/burp procedure. I did this before with our old mci 9 and it took me a couple of days of running it up to operating temp, then shutting it down. Waiting hours for it to burp and then adding coolant. Is there an easier faster way. On the side of the road on I-20 cooling down. This is slightly annoying.
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I found on my MC8 when refilling the cooling system it would help a lot to crack a pipe plug on the top of the right thermostat housing and the temp sender on the left. I would purge a lot of air doing that and also one other thing I ran into was the vent hose off the top of my right rad to the surge tank was blocked so that rad would not fill completely. I guess you probably know there is a bleeder at the back of the engine on the plumbing that feeds the bus heat system, at least there is on my 8. Just a couple things I ran into, Mike.
Thanks mike. Where is the bleeder? I wasn't sure where it was. I have an 8v92 mci 102c3. Stuck in a truck stop now until I can get her to burp
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The bleeder at the back of the engine is near the gear drive alternator on my 8. It is on a copper pipe 1 1/4 or 1 1/2 in size.
Scott, I just got home and saw your post. I may not be much help, but if you need another pair of hands, please call. I'm just north of Dallas, off I-35 around the George Bush Tollway/Hwy 121. Nine Seven Two Four Six Six Four Six One One.
Arthur
Thanks Arthur. I'm about to give a concert and then after I'll head back to the bus. It's at the pilot near the alliance airport
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So I'm on my way back to the bus. Going to try to add coolant after its been sitting about 5 hours. It should have burped enough by now to allow me to add coolant so if it doesn't let me add coolant, I'm limping it back to my friends shop in. Keene and bailing on trying to take it home to Michigan this weekend. We will just drive our land cruiser home
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If you have an IR gun I would make sure that your hunch is correct. Also it may show you the hot spots where the air is so you can find a more direct way to get the air out.
Rick
The engine should fill with water from the bottom and there should be a return water line from the top of the engine to the purge tank. My 8V92 had petcocks on both sides at the top of the engine to let the air out.
Jack
Ok thanks guys. I tried to add coolant last night and nada. I can't seem to add more even after coach cools completely. Not sure how water is added from the bottom but it makes sense. I guess I need to find the two bleed petcocks and try to purge. I will be headed back to the pilot this morning where we abandoned the bus. I'll limp it the 40 miles back to my friends shop here in Keene. Then I have to sort this all out. I do have an IR gun. I'll take some video of my readings. I need to know if this is a tstat issue, water pump issue or air pocket issue. I'm assuming nothing else can cause overheating as long as blowers, radiators, and blower box deals are good which mine all are
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Scott,the T stat housing on the left side above the water pump have plugs in the top to bleed the air also,if you have a hose going from the T stat housing back to the surge tank it should bleed with out doing anything
Thanks cliff. Okay here's the deal. We just pulled over because the transmission began shifting funny. Got out and saw that the transmission floor pan was smoking. I checked the temperature with my I are gone, and the temperature was 300°F. So I think that we have a smoked tranny. ALLISON HT748 ATEC. Would a tranny torque converter problem cause the engine to overheat? We have not been able to bleed any air out we cannot add any coolant and there are no hotspots on the thermostats or the pipes. Everything seems to be normal with the cooling system. Blower boxes sealed, blower fans are blowing. I think that maybe the transmission is not engaging properly, and it's causing the bus to work harder and cause it to overheat. Is this an insane theory?
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When you put water in the tank it goes to the bottom of the water pump to fill the engine. There should be a hose from the top of the engine to the bottom of the tank for the air to escape.
The transmission shouldn't be more than 10 deg. hotter than the engine. You should have an oil cooler on the transmission. It is cooled by the water in the engine. If the transmission is slipping it will overheat the engine. Make sure the water is flowing through the transmission cooler. Make sure you don't have a brake dragging. Take the coach out of gear and see how it slows down.
Jack
Do you have retarder on the transmission? Power seem ok until this happened? Either way it sounds like your overheating your engine through your transmission oil cooler. Did you smell the tranny fluid? If it smells sickly sweet and stinky you may be all done with that transmission. 300 degrees is really hot at the pan. It's weird though you should've either felt it slipping or you should've felt the drag of a brake hanging up or the retarder kicking in when you let off the gas, Felling bad for you Scott, I know you can use this like a hole in the head.
keep us informed
rb
Lol Rick, you know I've been bussing for 6 years now so nothing fazes me anymore. Got the bus back to my friends house with his makeshift shop. We both definitely think it's the retarder hanging up. Brakes are not dragging, coach rolls freely in Neutral. No slipping really on the Trans but it shudders as is slows down. Retarder feels like it's partially engaging or hanging up. Let the coach cool, and drove it the rest of the way to friends house and it never overheated and Trans never got hot. So this is intermittent. But all symptoms and my research point to retarder engaging causing issues. Guys, thanks for your support an sympathy but honestly, we aren't stranded, I have three amazing buddies here that have a lot of big truck and heavy equipment experience, and they have a shop with enough tools and forklifts to swap the tranny out, and the best part of this is the guy who sold me the bus here in Dallas called me today and told me he would give me the spare 748 and control pad he has at his house for free because "it's the right thing to do" so I won't be out $$$ for this, but definitely need to sort out if the harness plug is corroded and causing the problem or what. Is there a way to manually disengage the retarder and disable it?
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Quote from: Scott Bennett on June 28, 2015, 10:29:44 AM
Is there a way to manually disengage the retarder and disable it?
My B400R has a switch on the dash to disengage retarder. I thought that must be a standard item, but maybe not.
Good luck, Scott.
Jim H.
Do you have a switch on the dash but the switch has always been in the off position for the retarder. I just talked to the former owner of the coach, and he told me that I can back off the air regulator in the engine compartment for the air solenoid that enables the retarder. This is supposed to disable the retarder. I'm going to do it now and test drive the coach and see if I can get it to overheat again
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There's a Norgen (or other brand) electric solenoid that opens the air flow to the retarder. You may be able to follow the air line to where it is. Just unplug the electrical connection and it will not allow any air to the cyclinder. Of course, the vavle could be bad, which is allowing air flow to the retarder all the time, even when it is not suppose to be on.
Lucky, so I talked
To the previous owner and he said the same thing, told me to turn the air off at the regulator for the retarder solenoid. I did and this solved the issue. Doesn't appear to be overheating now :)
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So wanted to follow up this thread with my results:
My coach was overheating like crazy for days and couldn't figure out why. When I reached into the engine compartment and spun the knob on the air regulator that controls the retarder solenoid, it solved the problem instantly. I just finished driving from Texas to Michigan pulling my 6000 lb land cruiser and running 70-75 mph and she never overheated once even up long grades. So if you have a retarder, and you're overheating, disable it as a part of your diagnosis.
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