Prevost cooling

[MagnoliaBus]

Hi everybody,

I'll be starting my bus coversion soon. Since the 8v92t is sensible to overheating, i think that i will modify the cooling system. I plan on removing the original radiator. I will also remove the big a/c compressor. Then, i would install two radiator, one on each side with an hydraulic motor powered fan. A temperature controlled proportional valve on each thermostat housing will control the fan motor.
I think that two rad with 5 pass will be better than one with 7 to 9 pass as it will double the cooling area. Also, it will also be easier to clean. Technical papers on radiator show that air flowing thru the 6th pass is already saturated with heat.

So, what do you think about this idea ?

[PP]

Hey Denis, I think you're going to find a lot of guys on here with Prevosts and 892's are going to tell you that we don't have a heating problem. I've pulled some long grades with mine and she's barely changed on the temp dial with a toad. My advice is not to fix what ain't broken, but that's your call. Good luck with your project, Will

[Jon]

Denis,

If you have the original system in good condition you will never overheat. Those who have fought heating problems likely had issues brought about by poor maintenance. I don't know why but the use of the wrong coolant and lack of the required coolant changes and maintenance of the chemistry of the coolant seems to occlude the radiator.

I put 250,000 on mine and I could drive it like I stole it. Even on the hottest days it would run between 175 to 185. Pulling a heavy toad up the steepest hills on the hottest day would drive the temps up to 195, well under the 215 that would have DDEC derate or shut it down.

Recore the radiator, make sure the engine is clean and free of scale and build up from silicone drop out and make certain the fan shroud is in perfect shape, the fan is close to the shroud all around so it pulls air efficiently, and that you have no full width mud flap across the rear under the bumper and you will not be able to overheat it unless you lug it going up a 6% grade on a 100 degree day.

[scanzel]

I just made a round trip to Ohio USA 530 miles each way through NY/PA on I81,I80,I77 etc and they have some steep grades and temp rarely went past 175 outside temp was mid 80's. With my spicer standard I was in high gear at 55 to 65 mph going up and coming down the grades.

[MagnoliaBus]

Thank you for you opinions, it's good to know that the cooling system is well sized.
It's just that i don't like all those belts... and i would prefer the fan to run only when needed wiyh an hydraulic motor.
My only concern is the hydraulic line and fitting...we lost a couple of bus here in Montreal from fire due to hydraulic oil leaking from the radiator fan motor on the exhaust manifold and/or turbo.
So i guess from what youre saying that one good rad should be enough. Also, i could use the right side of the engine bay to relocate the engine batteries, since i would put the fresh, grey and black water tank in the storage bay in front of the drive axle.
I know the adage that if it's ain't broke don't touch it...but it's more like i want to build as much as possible a new vehicle.

Denis

[Jon]

I know a lot of folks are confident they have better ideas for their coach than the engineers that designed the coach originally, but in the case of cooling the engine manufacturer imposes very strong requirements the coach manufacturer must meet before the engine manufacturer will provide engine warranties. When guys decide to put in larger engines or increase the HP of the engines they are starting all over again because they have to design a cooling system capable of handling the new increase heat loads.

The amount of money the coach manufacturer spends to design, test and certify their cooling system is staggering.

[Beesme]

I've driven my 8v92 10k in last year . Texas st 110 deg Georgia at 95 and Michigan at 95 and I've never hit 190 degree no matter how hard I'm running ! I agree when these rigs were made they did not overheat .

[MagnoliaBus]

Well, glad to hear you all saying that it's not prone to overhating.
I agree with Jon regarding the engineering of a cooling system, it must be well sized.
Working in the engineering department of a large transit authority, i know first hand what's involved in the design of powertrain group. That being said, i have no knowledge regarding a coach since it's so different. Thank you all for your input.
I guess i must have read only worst case history on some blog...plus the fact that the bus i bought had the engine replaced because of overheating.

[Jon]

Denis,

Overheating is a topic that has been discussed often on forums, but what is often unknown is the history of the system and if it has been maintained, if the engine has been replaced or has had more HP added. As originally designed the systems have all done a good job, but as coaches age or get upgraded things change. Silicon dropout, especially from the use of the wrong coolant can quickly plug a radiator and I remember seeing photos or the tubes almost completely choked. Adding HP adds a lot to the amount of heat that has to be rejected, and add that need to a system that needs a good flushing or rodding and the potential to overheat rises significantly. Then what we cannot tell from some posts is how the coach is driven. If you are pulling a hill and the temperatures are climbing because you are lugging, the best thing to do is drop a gear and get the RPMs back up so the fan speed is up higher to draw more air.

Maintain the cooling system, drive properly and you are going to be OK.

[MagnoliaBus]

Hi Jon,

I know nothing about the condition of the engine (except that it run fine and there's almost no smoke at the tailpipe). The previous owner told me that the replacement engine came from a fire truck...but then he also said that they kept the turbo from the overheated engine because it was in better shape...go figure.
Anyway, i will clean the block the best i can. Replace hoses, thermostats and put a new rad.
I also plan to replace all the sensor and engine wiring ( well, more like the complete bus wiring).

[muldoonman]

I've driven my 8v92 10k in last year . Texas st 110 deg Georgia at 95 and Michigan at 95 and I've never hit 190 degree no matter how hard I'm running ! I agree when these rigs were made they did not overheat .

I know my 1991 Prevost with 86,000 miles since new will climb to 195 and you have to watch it in this Texas heat on any hills around Central Texas.. I pull a 2013 Ford Supercrew 4X4 and watch temp gauge like a Hawk.. Weighs in at around 40,000 lbs. plus pickup truck. Prevost has changed fluid (anti freeze) out  since I've owned it, about 20,000 miles ago. Radiator, belts and everything working like it should. Still will get up to 195 or over if you hog it..

[luvrbus]

You need to watch the heat even with the Prevost cooling which is a good system,I was over at Williams today in Phoenix they have 2 older Prevost with 8v92 that are cooked well done and 1 was a DDEC the owner kept using the override switch

[Jon]

It is very hard to protect engines from dumb things owners can do.

[MagnoliaBus]

For this old engine, descaling the block will be the most important thing to do.
Then after rincing many cycle i will replace hoses, thermostats, the water pump and the rad. That should be enough. I hope....

[Beesme]

Yes totally agree on the owners and the drivers. The 8v71 in the 4106 that I watch temps like a hawk . That trained me to watch the 8v92 . I don't get why it doesn't go over 190 she runs 170/180 all the time . Going  over mtns yes 190 but never over . Maybe the huge rear mounted radiator and side engine hatches all the heat blankets wrapped on exhaust and turbo helps . Or just Newell knows how to keep a coach cool lol