Author Topic: Oil Temp Out Of Control (Read 1103 times)

BUSDADDY · « **on:** May 19, 2006, 09:08:07 AM »

We've been dealing with a single relief 1600 with a doghouse on it that is running 200+ deg. on a cool day. Oil warms up within 10 minutes and runs 160 sitting still, hit 220 and climbing on Wed. on a 4 mile 40 mph drive.

It's a recently rebuilt engine (Duane) that's getting 40 lbs oil pressure idling and close to 60 driving. All tin and seals in place and working. 15w40 oil.

We installed a new cooler thinking it might be blocked but no change. Guage is accurate ( two different laser thermometers show similar temps all over case and sump.)

I'm thinking there's so much pressure that it's lifting the bypass valve and missing the cooler completely. going to check today if it's got a grooved bypass piston.

I'm looking for suggestions here, case is not tapped for full flow. and it's in a 68 bus so not much room behind the pump.

Should I put a stronger bypass spring in (blow up the cooler?) or an in/out pump and an external cooler? Heavier oil?

Hmmmmm.........

68IIIbuggy · « **Reply #1 on:** May 19, 2006, 04:15:07 PM »

Might be a dumb question, but have you checked simple things like Ignition timing, plugged carb jets, vacuum leaks, etc?

Bruce · « **Reply #2 on:** May 19, 2006, 05:37:35 PM »

Quote

15w40 oil.

I'm thinking there's so much pressure that it's lifting the bypass valve and missing the cooler completely.

You are correct. Excessive pressure causes the oil to bypass the cooler.

Checking the springs and plungers is a good start. You could also ask Duane what he installed.
An easy first thing to change is to go to 10W-30. The lower viscosity oil will reduce your pressure, allowing your engine to run cooler.

40 and 60psi is way too much.

BUSDADDY · « **Reply #3 on:** May 19, 2006, 05:59:36 PM »

Hmmm... Thanks Bruce, I didn't consider a thinner oil, when I have aero engines running high temps the fix is to go to a thicker oil but there's no pressure bypass for the cooler, usually just a temp valve and a strong cooler. Owner was going to ask Duane what went in to the oil system but I haven't heard what he said, might just go visit Duane tomorrow myself.

I agree 40-60 is way too much of a good thing. My own 71 bus has around 5k miles on a stock rebuild and it runs 8-10 at idle and 40 at cruise. 110 deg temp most warm days, peaked at 150 last thursday when it was hot out. Hits 190-200 on the freeway doing 70 for 1/2 hour +.

As to IIIbuggy's question, yes, checked all that as soon as the guage was installed and we said HOLY CRAP THAT'S HOT! what's causing that?.