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1990 4.0 runs hot and is eating oil

DPC

NAXJA Forum User
Location
Washington
approx 10,000mi on a rebuilt motor and now it is running hot, the coolant is brown and I am using approx 2 quarts of oil a week. There is no smoke while at idle and very little puffs of smoke with accel(but it is blue). maybe a cracked head? or??????????? any ideas
also no visible water in the oil.

thanks
 
Have a radiator shop or a good mechanic do a sniffer test of the coolant for hydrocarbons from a leaky head gasket.
 
Whenever you encounter an engine with mysterious looking coolant and/or oil consumption, the FIRST thing you should do is run a compression test.

It will tell you an awful lot for very little effort.
 
AZ Jeff said:
Whenever you encounter an engine with mysterious looking coolant and/or oil consumption, the FIRST thing you should do is run a compression test.

It will tell you an awful lot for very little effort.

Agree 100%. That would be the first thing to do. I suspect there could be a combination of leaking head gasket and leaking piston rings, so another rebuild might be on the cards.
 
Ok. Took it to my mechanic freind. He said pull the plugs and look. So......... compression is 165/175 across the board except #2 is 155. The plugs are all equal in color but are covered in a brownish ash looking hard deposit that chips off if you use your fingernail. The pistons are black from all I can see. I did a complete coolant flush till it ran clear. Then replaced with prestone n water and i guess i will see how it goes. It runs great. No signs of blowby through the valve cover so maybe just the valve guide seals got toasted when it was running hot??? Ever have it run hot after you get off the freeway but do good around town??????

I dunno

Thanks for all the help
Dan
 
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