More Overheating

[Glennman]

Took the bus to the lake last weekend. Sunshine, 100 degrees, nice trip for the most part.

However, besides all my posts that explain my overheating issues, this time was different. I couldn't hardly get it to 60 mph on the flat, AND it would start overheating trying. As soon as I would take my foot out of it ever so slightly so that I would pretty much maintain speed, it would cool down, then only a tiny bit of pedal would take the temp back up again, to the point where I had to pull over when there wasn't even a hill. When I bought the bus a year and a half ago, I drove it 1000 miles to get it home with relatively no issues. I got it up to 70 for quite a while on Interstate 5, and well over 60 on other 2 lane highways with no heating issues, with the exception of a couple of long hilly grades. When I pull over to let it cool, it drops to 180 within a minute or two (quite fast). I recently replaced the thermostats with 170 deg units.

I have read a lot on this board about possible injector issues, which is no issue to check out. It may be that all my heating issues I have complained about on this board is really limited to that. The only filters I haven't replaced is the fuel filters, so my plan is to change those, have the injectors checked, and hopefully that will reveal the problem.

Thanks for listening all you fellow bus-nuts. Glennman

[Jim Blackwood]

I don't know if it applies, but as someone who does engine conversions, we see a lot of overheating issues. When you put a large engine in a small car the cooling system can be challenging. There are a few general rules of thumb that can help. First, if it overheats at speed it usually means inadequate circulation or radiator size. If it overheats at idle it generally means inadequate airflow. Yours sounds like the first case. So provided the radiator(s) and engine are original spec and in good shape, the next place to look would be coolant circulation, including getting any air out of the system. Don't know how your bus is configured, but I'd guess it has some sort of header tank to evacuate any air. It's obviously circulating some coolant as it cools down quickly at part throttle and I don't know how you would check the coolant flow. Could there be any obstruction of the exhaust?

Jim

[buswarrior]

Ignore the complicated...

There's something very simple has to be doing this.

Did you confirm that your gauge is telling the truth? How?

While under way, someone has to shoot the pipes with an IR gun down thru the floor hatch, accurate reading sitting still means nothing about 5 degrees warmer. My old mc8, dash gauge was close at 180, and got climbed a lot faster than the temp showing on the pipes.

Air intake system blocked? Not just the filter, the rest of it too? Same as us wearing a face mask, overheat comes fast if the intake isn't clear.

100 degrees? That's damned hot where i come from... what is going on with radiator sealing? Fan door sealing?

If you can't gold plate the basics, the rest is a distraction and waste of time

Happy coaching!
Buswarrior

[muldoonman]

If front is electric,,, My electronic gauge in the dash reads 10 to 15 degrees hotter than the mechanical gauge in the back.  A Infrared Thermometer heat gun is your friend.  Oil pressure the same and about 10 to 15 pounds different , higher on the straight mechanical one in the engine bay. Scared me at idle when I first bought it 10 years ago and had sending unit replaced and it still was the same. Mechanic at Stewart Stevenson showed me the diff.

[luvrbus]

What is the turbo boost PSI,is it a TA or T 8v71 ? a lot to take into consecration chasing heating problems on the 2 stroke, could be just the impeller on the water pump has come loose then the killer to much HP for the cooling system to handle,injectors will be way down on the list when I check for overheating on a MCi 

[oltrunt]

My MCI9 would overheat in a second under full throttle and cool back down even faster.  I pulled the radiators and both were new.  I tested (and replaced) the thermostats to no avail.  All the factory shutters and air seals were in and working.

When I pulled the cover off the water pump I found my problem--a brand new pump whose impeller hadn't been tightened down was causing  the coolant to circulate by convection alone.  After tightening the impeller and replacing the square "o" ring (thanks Clifford) the over heating problem was solved.  Jack
.

[Glennman]

I'll have to try the laser gun and check the mechanical gauge and compare with the electronic one. When I'm parked and temp at front is 180, the laser showed about 155 at the stat housing, but that was a few days ago, so I really don't remember for certain. I'll also try checking the pump impeller. That would be crazy if I had the same problem!