Repairing 420 oil pump and head gasket

[lherseth]

Last fall I ran my 420 for a few hours and parked it, it ran fine. A few weeks later I was going to change the oil and when I drained it, the oil had anti freeze in it. A blown head gasket of course, I changed the oil and started it up so I could put it it the garage for winter repair. But when I started it, there was no oil pressure. I changed the gauge and still no pressure. Does anyone now why a blown head gasket would ruin the oil pump? I took of the oil filter and started the motor and a little oil would flow out of the filter housing. There seems to be a little pressure, can I drive it a 100 yds to the garage without wrecking the motor? I see in the manual it says its a splash type oil system.

[JD in Canada]

If it ran with the coolant in the oil too long it could have wiped the bearings causing one of them to spin. I'd check my main and rod bearings if it were me.

Last fall I ran my 420 for a few hours and parked it, it ran fine. A few weeks later I was going to change the oil and when I drained it, the oil had anti freeze in it. A blown head gasket of course, I changed the oil and started it up so I could put it it the garage for winter repair. But when I started it, there was no oil pressure. I changed the gauge and still no pressure. Does anyone now why a blown head gasket would ruin the oil pump? I took of the oil filter and started the motor and a little oil would flow out of the filter housing. There seems to be a little pressure, can I drive it a 100 yds to the garage without wrecking the motor? I see in the manual it says its a splash type oil system.

[Lavoy]

If there is enough anti-freeze mixed in the oil, it will get really thick. I would drain the oil, and put in fresh oil then try it.
Lavoy

[The Fireman]

My 440 had anti freeze in the base when I bought it from the head gasket (previous owner re used the gasket after installing a new head ) I drained it out then cranked it until I got oil pressure. Loaded it onto a trailer and brought her home. I dont think it ran long with the anti freeze in there but it was long enough to do some damage to the bearings, but not to the crank.

I would definatly drop the base and check ALL of the bearings, the first one i pulled looked decent but the rest all showd signs of damage. If it were me I think I'd tow it in to the shop, mine had good oil pressure still so I figured I was safe to run it, with no oil pressure I wouldnt try to drive it.

[H-D]

It's not that your oil pump failed, rather the bearing clearances have opened up due to a chemical reaction between the antifreeze & the babbet metal in your rod, main, & cam bearings. Normal oil clearances are on the order of .0015"-.002" this will open up to the .015"-.020" range when the babbet metal sloughs off after contact with antifreeze. I didn't believe it either 'til I wiped off a main bearing from my '58 Cadillac with a rag that had a 50% concentration of antifreeze on it. After a three hour dinner break the insert was growing "warts". Don't feel like the lone ranger, I've seen this happen on Cadillac 4.1 liter wet sleeve & Chevy 3.1 liter engines so often that I won't give an estimate on one without tasting the oil/water condensate at the oil filler cap.

[Tigerhaze]

H-D

Thanks for the explanation- I've known that contact with antifreeze causes the bearing clearances to be excessive but really didn't know why until now. I'm assuming that simply cleaning the impacted surfaces and replacing the bearings will solve the problem for the most part, or do I need to worry about the crank/cam journals themselves too?

[H-D]

I always mike the rod journals & plasti-gauge the mains. You know of course to check the back side of the inserts for journal undersize condition. Nephew didn't; put standard rings & bearings in a 040" overbore engine with a 010" shaft. Very poor out come. These ol' girls are tough, good steel & slow turning to boot. There's little chance you harmed the journals with the limited amount of time you ran her in an insulted state... however, you don't know her history. Reckon I'd be cautious.