Thread: Bus is overheating.

Tweet

I've got a problem with the bus overheating around town, long steep inclines, or in heavy traffic.
I thought I could get around it by putting a smaller pulley on the fan.
That won't work; I'd forgotten it's an electric fan.
Doh!
Are there any 'after-market' type kits out there for a Chevrolet Vortec 400ci motor to enable me to mount a mechanical belt-driven fan?

I realise I won't be able to do anything much about it until after the Silly Season (Christmas and New Year,) is over; but if I can start getting ducks in a row now it could be organised for early next year...hopefully...

John, is your electric fan mounted on a shroud panel to pull air through the entire radiator core? On the '33 there's an aluminum panel standing off the core an inch, with the fan mounted to the panel, and it works great!
-
20201210_123249.jpg
-
It's really congested on mine, and I doubt you have the aluminum radiator but looking at the top left you see that it's simply a piece of flat aluminum sheet with the four sides folded down about an inch, then the sides are folded out to form a bolting flange. The result is a box standing off the back side of the radiator about an inch, with a 16" hole cut in it for the electric fan. I neglected to turn on the fan power once, and after idling around for 5 minutes I glanced at my temp gauge and it was up well over 250F! Punched the power button, the fan kicked on high mode and I watched the temp gauge fall, back to the normal 185 indicated, 195F at the heads, in short order. Just a thought, if you've just got the fan surface mounted.

Jon, does your water pump have threads on the water pump for a fan clutch?

Roger: Yep, there's a fan shroud, it's plastic with a 16" fan mounted to a lattice work right in the middle of a 17" hole. The shroud itself is solid, so all air is sucked right through the centre.

Ryan: It's pretty cramped down there, couldn't see much even with a torch and reading glasses, so did the braille bit and ran my fingers over the whole pump. From what I could feel there were no 'spare' holes anywhere on it.

The core is brass, measuring 21 1/2" wide x 22" high and 3" deep. We put it in when we dumped the flat-head and put the Chev motor in. Its been out twice since then, the last time would've been three or four months back when we were blaming a faulty pump for the problem, and the radiator got checked out as well.

It was after that that the idea of speeding the fan up raised its head.

If a mechanical fan doesn't work out you might look into using an OE electric fan.

Seems like the "hot ticket" a few years ago was using a fan from a Ford Mark something or other. Some were 2 speed and supposedly moved more air than almost any of the aftermarket units.

They were larger (deeper) than the aftermarket units, but if you have the room.....

Here's a link I found.

https://www.hotrod.com/articles/1005...ooling-system/



.

i think you will end up with an aluminum radiator to fix it . i use flexlite syclone fans . never had any heat problems .

I've used several MKVIII, Taurus, and occasional Viper ($$$$$$$$$) electric fans and aluminum radiators on many types of cars from the early 30 types up to some Cobras with some big hp engines.

You don't want to use smaller crank pulleys to gain one or two HP as you lose water pump and alternator speed--------
Go for the highest amp draw electric fans as thats a better rating system than those stupid 1500cfm---------

Originally Posted by johnboy

I've got a problem with the bus overheating around town, long steep inclines, or in heavy traffic.

No disrespect meant and you probably have already checked, but I gotta ask.
Idle, low speed and light load over heating can have several different cause, one, several or all can contribute.
* Low initial timing (sometimes moving vacuum advance from port to manifold fixes)
* Too lean fuel mixture at idle and transition circuits (richening the idle circuit sometimes helps)
* Insufficient low speed air flow, this one gets tricky because there are several causes of this,
A). Low voltage/amperage output at low speeds
B). Undersized wiring
C). Air flow restrictions (small grill opening, A/C condenser)
D). Undersized electric fan motor (there’s more to this)

JMHO;I would check and adjust initial timing to 12° -15° (this will probably require adjusting the distributor’s mechanical curve). Then follow that with adjusting the vacuum advance to add 10° at idle and cruise. I would then check/adjust the AFR at idle, transition and cruise circuits. Next I’d check the front of the radiator for air flow restrictions, often it is the A/C condenser mounted too close to radiator blocking air flow (1” space between rad and cond with sealed edges preferred).

After checking/adjusting the above, if the heating issue is still exists, I would check the wiring from the battery to the alternator, and the supply wiring to the fans to be sure they are sized large enough for the current demands.

Next I would check the alternator’s output to see if it is providing the current needed at low speeds.

Lastly (and this could be argued it should be checked first), I would check the CFM output of the fan and compare it to the current demand of the motor (I’ll explain this better below).

Many electric fan manufactures use a misleading rating for their fans “CFM" at no load. To me this is an OXYMORON, as there can not be a CFM rating worth its salt at NO LOAD. The load would be the power required to turn the fan blades at speeds sufficient enough to output the rated CFM (they cheat by using formulas on paper comparing the motor’s RPM at no load and the coefficient of the blades pitch and draw at that RPM), however as the load is applied the motor speed drags down from insufficient horse power (amps).

AND, many (too many actually) fan companies do this NO LOAD rating, resulting in unsatisfactory performance and consumers left scratching their heads trying to figure out why it’s not cooling. 2000CFM from a 5 amp motor AIN’T gonna happen.

If your fan is rated at xxxxCFM, but the motor’s current demand is too low (current demand is what the motor uses to operate and another way of gauging horsepower), it just can not perform adequately. Your fan’s electric motor’s demand should be at least 15 amps for a 16” fan (25 amps on a high output fan), and this leads into the next part of the equation (supply wiring and current available).

With higher current demand, higher outputs are required, the alternator and/or wiring may be undersized, and this leads into the old saying “there are no FREE lunches”. If the current demand is not available, the voltage drops, which in turn increases current draw and the cycle spirals downward.

Everyone buys into the ELECTRIC FANS gain horse power, while it's true when the electric fan is OFF, it's not true when operating. When all things are equal horse power is horse power wether mechanical or electrical.

Sorry for the book……….

also remember the 400 had an extra "steam" hole in the heads & gaskets, are you sure the correct head gaskets was used

Originally Posted by 36 sedan

Sorry for the book……….

But it's a GREAT book!

JB, I went with a SPAL fan which is 2 speed, rated by amp draw and I opted for the SPAL Programmable Controller that operates the fan automatically, low speed above 195F, high speed above 210F and back to low speed below 200F. Turning on the AC (very rarely used) triggers high fan speed. At normal cruise the fan's not running, even on a hot, humid day.

Add an oil cooler.

Crikey!

Thanks for all the info, I'm a bit overwhelmed!

I've copied it all off; now I'm going to have to sit down and read it all and try to assimilate it.

Thanks again to you all, much appreciated!

JB, I haven't seen it mentioned anywhere but, have you verified the gauge? Do you know it is REALLY overheating? An inexpensive laser temp gun can help verify this or an appropriate thermometer... Also,what is "overheating"? Is it boiling over or just higher than usual?

And thanks as always for the monthly "updates"... Chris and I wish you ( and SHE!) all the best. 8-)

The gauge is accurate.
It's boiling when the needle goes up around the 250 mark, and is verified when water and steam bubbles out all over the place.

So yep; it's pretty damned hot alright!

(And thanks for your comments re my 'updates'. Some days are good and some not so good. You get used to it. )

jb, with everything that's been offered my bet is either 1) Inadequate fan airflow/power/current draw (bad fan selection), not giving you what you may believe to be the "rated air flow"; or 2) Inadequate conductor size providing power to the fan, resulting in reduced current to the fan, reduced airflow and poor performance. In my book you need a top quality two speed fan operating through a relay to provide full power, and a good fan controller to stage the fan operation based on coolant temperature. Just my $0.02, and just to clarify, is it correct that your fan is pulling air through the radiator, not pushing? Pusher fans tend to restrict airflow when they are not needed, increasing coolant temp to the point that they run more than a puller.