'Honin In On The Heat

oltrunt · April 16, 2015, 06:25:18 PM

When I was bringing my prize home ('90 MCI 9 8v92), I discovered that on the slightest hill the engine temp climbed and the auto shut off kicked in. By the time I got to the side of the highway and out of traffic the engine had cooled enough (to about 195 degrees) to start and go again. Once on the flats the temp stayed at 170 degrees even at 65 mph. Since the bus has sat un-run now for 6 or 8 weeks, I decided to start her up and check out the cooling system. The water level was up, the belt was tight and when I turned the key the DD fired off instantly! Kind of scary that it starts so fast. I set fast idle and brought the temp up to 170 degrees (front and rear gauges agree) and let it run a while--it remained at 170. Incidentally, the cold start oil pressure was 25 lb at fast idle and dropped to half that at slow idle and operating temp. Also, the air pressure reached 120# in three minutes and pop off (120#) pressure in five minutes.

I didn't think far enough ahead to bring my IR thermometer with me but my fingers were able to gather a lot of info. After running the bus at operating temp the radiator hose to the top of the passenger side radiator was HOT and the return hose to the engine was pleasantly warm. On the drivers side, the upper hose and about an inch of the upper radiator core was HOT--the rest of the radiator core and the lower hose was COLD.

So I asked my still wrapped in a protective layer of wax paper crystal ball if it was the thermostat or a plugged radiator core and I got a sort of fuzzy answer--rad-ther-torstat. What say you? Thanks for the read and any insights you can provide, Jack

solodon · April 16, 2015, 06:48:41 PM

I'm VERY new at this however I'd go with the thermostat. It's cheaper and easier to replace. HOWEVER since the output of the radiator is warmer than the other side a restriction in the radiator is a reasonable assumption also. Maybe back flush the radiator and see what comes out?

I really have no basis for these statements.

oltrunt · April 16, 2015, 07:06:25 PM

solodon, it seems you have the same crystal ball as I Ha, Ha. Thanks Jack

luvrbus · April 16, 2015, 08:00:46 PM

I would replace both T stats and seals in the housing the seals goes bad and the water flow is diverted I find the seals to be 85% of the problem most of the time.I don't what you have there with a 170 degree T stat you should be running around 185 degrees as they use a partial open style T stat.

Do you have a temp gauge for each head ? if not you need it on a 8V92 and I would check the oil sounds like the engine has 15/40 for oil that is not great oil pressure for a cold 8V92 on start up with fast idle it should be 50 to 60 lbs unless the gauge is off.Regardless if you didn't change the oil and don't know what oil is there change it to Delvac 1240 then you know for sure lol the Delo 100 guys will be around shortly

good luck that is a tough engine to cool in a MCI unless it is a D model

boxcarOkie · April 17, 2015, 03:22:36 AM

Quote from: solodon on April 16, 2015, 06:48:41 PM
I'm VERY new at this however I'd go with the thermostat. It's cheaper and easier to replace. HOWEVER since the output of the radiator is warmer than the other side a restriction in the radiator is a reasonable assumption also. Maybe back flush the radiator and see what comes out?
I really have no basis for these statements.

Now THAT is refreshing. Three words you will never see on a bus board. I Don't Know. It is nice to see something different for a change.

BCO

Scott & Heather · April 17, 2015, 08:34:19 AM

^I'm with you lol. So in that spirit. "I don't know" what I would do without this bus board. You guys are a huge blessing in our lives

Ok, mushy feelings aside, are you sure your radiators are full? No air bubbles?

oltrunt · April 17, 2015, 10:30:04 AM

Scott, I don't know how I'd check that without removing the hoses. I do see a rise of water level in the sight glass in the reservoir tank as the engine warms up if that tells me anything. Jack

buswarrior · April 20, 2015, 06:37:30 PM

T-stats and seals as noted by luvrbus.

And religiously check the seal around the fan door, and around the radiators, including their cover doors. Every whisper of air sucking in somewhere other than THROUGH the rads, is lost cooling.

The T-stat job will be a big improvement, leaking fan air is the next low hanging fruit. Then comes the 2 parts rad flush from DD...

Happy coaching!
buswarrior

chessie4905 · April 21, 2015, 11:10:52 AM

You can surely do whatever you wish, but If that coach was mine; just purchased, 25 years old, I'd pull both radiators and have them cleaned, rodded out or re-cored if required. Then I would know what I had. I am assuming it has the original engine size and not a transplant with under sized radiators and cooling apparatus.