390 Engine Problem
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New User
Joined: Sep 2002
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From: Madison USA
390 Engine Problem
I recently (2 days ago) purchased a 1968 F100 with a rebuilt 390 that has been heavily modified. It has a C-6 tranny, 750cfm Holley carb, Comp cam .560 lift (292H), headers, electronic ingnition, 4.11 rear, and much more. When I bought it I knew it had this engine problem and am asking this question to see if anyone has any insight before I tear the engine apart. Here's the problem. Oil is mixing into the radiator and the fluid has turned gray with a greenish tint. The fluid is more viscous than oil and is also quite sticky. Nothing is mixing into the oil. I'm hoping it isn't a cracked engine block although I do have an extra 390 block. Any tips or advice would be greatly appreciated.
Postmaster
Joined: Apr 2002
Posts: 3,613
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From: Coal country
390 Engine Problem
You have oil mixing in the coolant most likely because of a
1. Blown head gasket;
2. Cracked head;
3. Cracked block.
DON'T run that engine any more. You may need to pull it to have it degreased from the inside out, and may cause more damage if you continue to run it.
Have your heads magnafluxed for cracks; they'll show up right away.
1. Blown head gasket;
2. Cracked head;
3. Cracked block.
DON'T run that engine any more. You may need to pull it to have it degreased from the inside out, and may cause more damage if you continue to run it.
Have your heads magnafluxed for cracks; they'll show up right away.
Elder User
Joined: Mar 2002
Posts: 609
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From: Watauga TEXAS
390 Engine Problem
If you have your tranny cooler in the tank of your radiator, take the tranny lines off and then pressure test your cooling sysetm. If the cooler has corroded, coolant should leak out of the cooler ports. Engine oil has a hard time getting into the cooling system- it's usally coolant that finds it's way into the oil because coolant is under full pressure wihtin it's entire system, where as oil is not- doesn't mean that it can't happen, though.
Good luck-
Joe
Posting Guru
Joined: Oct 1999
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From: yes
390 Engine Problem
>it's usally coolant that
>finds it's way into the oil because coolant is under full
>pressure wihtin it's entire system, where as oil is not-
>doesn't mean that it can't happen, though.
I'd have to disagree with that just because when the oil is pressurized it's at a much higher pressure than the coolant is, a possible place to look for that I've heard of is the oil passage from the cam bearings to the cylinder heads, since it's under pressure it would put oil into the coolant. You can fix this by taking a pushrod cutting both ends off so that oil can still get through and reaming the hole to fit and pressing the pushrod in.
>finds it's way into the oil because coolant is under full
>pressure wihtin it's entire system, where as oil is not-
>doesn't mean that it can't happen, though.
I'd have to disagree with that just because when the oil is pressurized it's at a much higher pressure than the coolant is, a possible place to look for that I've heard of is the oil passage from the cam bearings to the cylinder heads, since it's under pressure it would put oil into the coolant. You can fix this by taking a pushrod cutting both ends off so that oil can still get through and reaming the hole to fit and pressing the pushrod in.
Elder User
Joined: Mar 2002
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From: Watauga TEXAS
390 Engine Problem
>I'd have to disagree with that just because when the oil is
>pressurized it's at a much higher pressure than the coolant
>is
You're correct about oil being at a much higher pressure. My reasoning for my statement is that pressurized coolant surrounds more surface area than pressurized oil. So the way I see it, the chances of coolant reaching the oil are better than the oil reaching the coolant- again I'm not saying that it can't happen, It most certainly can. It's just nice to be able to check other options before an actual tear-down and trip to a machine shop.
Ya'll have a great day-
Joe
>pressurized it's at a much higher pressure than the coolant
>is
You're correct about oil being at a much higher pressure. My reasoning for my statement is that pressurized coolant surrounds more surface area than pressurized oil. So the way I see it, the chances of coolant reaching the oil are better than the oil reaching the coolant- again I'm not saying that it can't happen, It most certainly can. It's just nice to be able to check other options before an actual tear-down and trip to a machine shop.
Ya'll have a great day-
Joe
New User
Joined: Sep 2002
Posts: 1
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From: Anchorage USA
390 Engine Problem
If you get any more ideas on this problem please let me know! I have a 390 with the same problem, oil in the water. The bad part is that I still have the problem after a new motor was installed and the cooling system flushed. I'm stumped!
Freshman User
Joined: Feb 2002
Posts: 25
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From: redwood city usa
390 Engine Problem
I had this same friggen problem and put a new motor it for abot 4 grand and had the problem again.... i finally found a very small hairline crack in my timing chain cover... replace the timing chain cover... with a new one or a known good used one... sometimes the cracks are too small to see
good luck
good luck
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Senior User
Joined: May 2002
Posts: 298
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From: Denver
390 Engine Problem
Where are you loosing the oil from, engine or tranny?
If engine- Could be head(s) cracked, Head gasket.
If tranny- do you have radiator W/ coller built in?
What is getting over filled, where is the leak going?
could beter help knowing more info.
Robert
72 F-100 Ranger XLT W/ 86 5.0L W/AOD
krazdndenver(No Email Addresses In Posts!)
www.geocities.com/krazdndenver
If engine- Could be head(s) cracked, Head gasket.
If tranny- do you have radiator W/ coller built in?
What is getting over filled, where is the leak going?
could beter help knowing more info.
Robert
72 F-100 Ranger XLT W/ 86 5.0L W/AOD
krazdndenver(No Email Addresses In Posts!)
www.geocities.com/krazdndenver
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Junior User
Joined: Sep 2002
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From: Mpls US
390 Engine Problem
Yessir I hope for your sake it's only a bad head gasket...was the engine rebuilt at any time? You need to know that your heads are not warped, sometimes the result of incorrect torquing when installed and that your block is flat within spec, it may need decking.A cracked head will do it too of course. If you're into it ,it's a start from scratch kinda thing -magnafluxing et.al- I'm happy to say my 390 didn't do that to me--check into some high end spare no expense type head gaskets,and re-torque per the instruction in the shop manual...a little at a time 
Postmaster
Joined: Apr 2000
Posts: 2,838
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From: SD
390 Engine Problem
A few years back, a friend had the same trouble with a 390 in a '72 F100. Oil in radiator, but no water in oil. Tried resealing intake, no help. Ended up tearing it down and found a cracked oil passage - like FE427TP mentioned. The machinist had to ream out passage and press in a pushrod (with ends cut off) to line the passage. It stopped the leak, it's still running strong years later.
Marty
Marty
Senior User
Joined: Mar 2002
Posts: 271
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From: La Canada, CA
390 Engine Problem
I want to re-emphsize what 73 custom and FE427TP suggested. 390's are notorious for that oil galley going bad. Easy fix. Do not overlook even if you find other suspect areas.