Blue Bird Engine Rebuild Question........

[Pete Masterson]

The number one killer of diesel engines, particularly 8v91 or 6v91 Detroit Diesels, is overheating. Compared to gasoline engines, diesels run higher internal temperatures due to the nature of the combustion process. Internal pressures are also much higher, causing much higher stresses on parts that then are prone to catastrophic failure when the additional stress of over-temperature operation occurs.Due to a variety of age-related and maintenance-related issues, the 100,000 to 150,000 mile period frequently becomes a time when cooling system issues become a serious threat to the health of the engine.

The coach I purchased (with about 110,000 miles on it) experienced hot-running symptoms on my maiden trip home. The first thing I did was take it to an appropriate radiator shop where I discovered that the radiator was totally packed with oily-dirt outside the area swept by the fan. This cut the cooling capacity substantially. The problem was also not at all obvious by inspection due to the metal shrouds on the inside of the radiator and the presence of the charge air cooler radiator covering the view from the outside.

This situation occurred despite my having requested the selling dealer to inspect the radiator and steam clean it at my expense "if necessary." The dealer claimed to have found the radiator satisfactory upon inspection. I inspected it myself (as best I could) during my vehicle acceptance inspection -- and could not see the blockage found later on.

I elected to replace the radiator core with a more modern and efficient design (rather than simply clean and replace the existing radiator). I part this was because of the substantial labor expense to pull the radiator, so it made more sense to re-core to ensure that it would not be necessary to pull the radiator again in 2 or 3 years.

I also made sure that the radiator was pressure washed or steam cleaned (preferred) at least once, if not twice each year.

Subsequent to the radiator work, the water temperature rarely budged above the normal 180 degree level, even under the heaviest loads.

I also watched the oil temperature carefully. While the owners manual suggested that oil was in the normal range from 200 to 250 degrees, the top-end seemed rather excessive to me. I set a personal goal of 230 degrees -- and I would pull over if the oil temperature ever exceeded that amount. On heavy grades, the oil temp would tend to hold right at 230 -- but if it started to rise above, then I'd stop and let the engine cool at idle for 2 to 4 minutes.

Unfortunately, as a buyer, checking for non-overheated operation is impossible. The "good news" is that operating at excessive temperature usually has immediate and obvious effects -- so if the engine appears to be operating normally at the time of inspection, it is likely not to have been subject to dangerous levels of excessive temperature operation.

The important thing is to be aware of the critical nature (and lack of forgiveness of) keeping temperatures below the maximum allowed level -- then taking all steps necessary to avoid overheating events -- including immediate action to moderate engine temperature when you see the _trend_ moving toward excessive heating.

Pete Masterson

(former) '95 Blue Bird Wanderlodge WBDA 42

El Sobrante CA

"aeonix1@mac.com"

On Jan 17, 2010, at 9:53 AM, "cmlintx@sbcglobal.net" wrote:

I have noticed that several of the 'For Sale' older Blue Birds (1990's) are advertised as having their engines rebuilt when the mileage is only around 100,000 to 150,000 miles. Is this because the owners did not know how to take care of the diesel and they did something wrong? What do I, as a want-to-be owner, check to verify that an engine has been cared for properly?

Thank You,
Clyde in Festus
Want-to-be Motorhomer