HELP!!!! I am running out of ideas to try. I pick up a 1996 Disco with blown head gaskets. I have since repaired it (by the book) and it seems to run fine. But once I get it out on the road she will start to overheat. I have check the fan clutch and it keeps spin when i put a newspaper in it, remove and ran w/o the thermostat then replaced it with a new one. The radiator fins are clean. I power washed it when it was out of the truck. When I flushed the system the the water flowed well. I burped the cooling system. I dont see any fluid running out with the exception of the overflow res. There is no water in the oil or oil in the water.
When I drive it for about 3 miles and come to my first stop. My oil light will come on then that is when I notice the temp gauge starts rising. A mechanic told me that the oil light is probably coming on because it is too thin for that age of an engine so I replaced the 10w30 with 20/50. it fixed it for a min but it is back again.
Has anyone got any better ideas. I think I have beaten my head enough and need some fresh ideas.

Thanks,
AJ


Adding: 150,000 miles.

 

Your best bet is to get a cheap set of gauges from your local auto parts or wal-mart and install them. For the 20 or 30 dollars you will spend on these, they will tell you exactly where the oil press and water temp are at. As for oil press you only need 10 psi for every 1000 rpms. So if your driving at 3000 rpms you will only 30 psi for safe engine operation. This spec is for stock engines only!!! As for water temps, anything over 230F should be checked out.

 

The first thing I'd do is get my oil pressure with a gauge, the light comes on below 8# normally, that's not to say your's is good.

The easiest way to get a gauge on it is with a filter sandwich, (I did) (glowshift. com)
3/4" x 16unl - fits between oil filter & block, has (3) ports for 1/8" tie-ins.

Put a 0-60 psi mechanical ga. right onto it for testing.

You may have a tired engine, causing generally low oil press.

I just replaced my rod bearings and picked up 8-10psi (2hr job)

I figured the bottom end had never been freshened(correct guess), so I installed std. brgs

$45 to my house, rovahfarm.com

You're oil pump could be worn, you're oil sump & pickup could be sludged, (mine had a piece of old gasket partially blocking it.)

The overheating, the fan should have resistance to turning when hot, and should roar, much less when cold

Is your fan shroud intact?

You may try some radiator cleaner, (not flush) cleaner is more intensive and requires driving around.

luck,greg

 

The radiators have a tendancy to clog up. At 150K and blown head gaskets, odds are someone put some kind of sealer in it before the gaskets totally gave out. Pull the radiator and have a shop backflush and flow test it.

For your oil pressure, I would manually check your numbers at idle and 2K, cold and hot. Then I would drop the oil pan and check for sludge on the pickup tube. How did the heads look when you pulled them? if they were pretty dirty, I would just move straight to the pan. As stated, the switch comes on at 8psi, and 20/50 is really too heavy. If it is coming on with that heavy of oil, you have a serious problem. 10W40 should be heavy enough.

 

Thanks folks for the great advice. I just noticed something on my last ride around the block.
Everytime I took the Disco for a ride I always returned with it pinged out to the H on the temp gauge and when I turned it off I would here the front electric fans run. This last time I made it back just before it was pinged out, only about an 1/8" from the H on the gauge and I didn't here any fans running with either the key in the on position or when it was off. Could that be the cuprit causing my O/H problem? If so, what switch or temp probe runs those fans and where do I find them?

 

Well first off since you kept driving it with the temp needle pegged on "H" you prob fried the engine, these are all aluminum engines and they do not like being overheated at all.

The electric fans running when hot with the key off is normal if the engine temp is to high.
Those fans are for the a/c and engine cooling is a overheat situation.
Turn the key on but do not start the engine, turn on the a/c, do the fans come on?
No? Bad sending unit in the a/c system telling the fans to come on.
If they do come on then look into the clutch fan being bad.
Check the tech section for a how to on that one.

 

I need to add, the hotter a engine gets the thinner the oil will get.
The oil can get so thin that it is to thin for the oil pump to pump or to thin to build good oil psi.

 

It Just reached the H when I pull into the drive. Never let it run once it hit the H.

The fans come on when the AC is on. So I take it they wouldn't have any thing to do with it not cooling the system. Just strictly for the AC?
I did a newspaper test on the clutch fan to see if the paper would stop it but it didn't, so I will have to assume the clutch is good.

 

The electric fans help cool the engine while the a/c is on.
Why would you ever stick something into a spinning fan? You looking to loose a finger or two?
The fan blades are just plastic, one breaks and comes flying off into your skull you wont care about it overheating.

Either your clutch fan is bad or the radiator is clogged.

 

Huh. My fans run all the time.