[Fixitup944]

Good Morning,
In a 1997 3.8L V6, which we sold to our son's best friend, the bf called the other day to say that the engine was overheating. His Dad, replaced the cooling fan motor and "checked" to see if the thermostat was working and reported that it was. But when they drained the oil it looked like coffee milkshake and just replaced the oil. The overheating problem continued until the engine was "bucking". I had them haul the car to my garage.
I drained the "new" oil only to find that it was like caramel coffee milkshake and there was approximately 12 quarts of it that came out of the oil pan. Upon draining the radiator I only found about a quart of coolant there.
So I have disassembled the engine to clean it all out and re-gasket everything. BUT I have found that there is NO thermostat in it's housing (I think that the Dad may have forgotten to put it back in after he checked it). The cylinder heads appear to be OK, not warped and flat where they are supposed to be flat. The gaskets looked like crap and were badly separated in a few parts.
Before I re-assemble the engine I want to determine what would have caused this so that I don't have to do this again any time soon. What are the chances that the problem would have been caused by a faulty water pump, or the abscence of a thermostat or some other source that I have not already mentioned here.
I appreciate any feedback and/or suggestions that you all might have.

[97S281]

As I understand it the lack of as thermostat would cause the car to overheat due to the coolant constantly cycling and not spending enough time in the radiator to actually cool back down. That would not cause 7 quarts of coolant to enter the oil system though. I would think you had a bad head gasket. The " coffee milkshake" is of course oil that has coolant in it.

[ckholloway]

Blown head gasket.. the thermostat could have cause heating issues but most often does not. It sound like it lost a head gasket and that's what caused all the problems with the heating issue.

[01V8MUSTANG]

Agree with the blown head gasket. When oil mixes with the coolant it looks like coffee w/cream. If you plan on replacing the head gasket make sure to check that the head is flat and not warped.

[goren813]

+1. If you've got the motor apart may not be a bad idea to replace water pump anyway depending on mileage. The bearing on mine was shot and causing overheating issues at ~145k.

[BML99]

As said, it's a head gasket. I dealt with one on my 1996 3.8L as well.

[mustangmike!]

Moisture has gotten in your oil some how. Replace the oil, and run it for a bit while looking into the valve cover, see what color it looks like.

[ESG-642T]

May want to look at a new motor if you had 12 quarts of oil/coolant mixture, bearings aren't a huge fan of coolant.

[walt1120]

running without a thermostat really doesn't do anything to the water temp once the car warms up. I have been running without a t stat since early june.

I would have dropped a load in my pants if i ever drained 12 quarts of anything out of the oil pan lol

[mcqueen]

Originally Posted by walt1120 I would have dropped a load in my pants if i ever drained 12 quarts of anything out of the oil pan lol

+1. I'm lucky to get 4.5 quarts of oil out for an oil change. If I got over double the oil back out of my engine that I put in, I just run oil through it constantly and sell it. Oil multiplying engine ftw

[Green_6er]

head gasket was blown. but i'm not sure about not having the T-stat. I personally would always make sure that my car had one before i would even think about cranking it.

[walt1120]

Originally Posted by Green_6er head gasket was blown. but i'm not sure about not having the T-stat. I personally would always make sure that my car had one before i would even think about cranking it.

it just takes longer for the motor to warm up since coolant starts to circulate right away. my t stat locked up in early june right before an hour ride home. it absolutely sucked i had to pull over 3 times to let the car cool off.

i just haven't felt like putting in the new 160 degree one i got yet

[Loki]

Without a thermostat, the coolant is constantly running thru the hot engine. You don't want to run without a thermostat. You're not giving the coolant any time to cool off before it cycles again. Not something I would do, personally, no matter the reason. Just get a different temp t-stat if it's necessary.

As far as that being the reason that the engine would heat up enough to blow a head gasket? I don't think it would have been that serious of an issue. There was another cause. I'd probably look at the water pump.. You don't want to reassemble the engine just to have the same problems continue to arise

[MustangV6Man?]

Hmm I got a 95 V6, one thats susceptable to abd head gaskets. Now granted, I have no clue if the guy before me ever changed the gasket or whatever, but what can I do to make sure this never happens cheap?

[mcqueen]

Originally Posted by MustangV6Man? Hmm I got a 95 V6, one thats susceptable to abd head gaskets. Now granted, I have no clue if the guy before me ever changed the gasket or whatever, but what can I do to make sure this never happens cheap?

There's really no way to ensure you never blow a head gasket besides replacing them occasionally. It's not horribly difficult to do on our cars if you know a little bit about engines and have the tools to do it. You'll need new head gaskets and head bolts for sure. That will probably run you somewhere around $80-100. And you might need new upper/lower intake gaskets if they get damaged while removing the intakes. Same for the exhaust manifold gaskets but they're not quote as easy to damage. If you don't mind working around the engine accessories you can pretty much just remove the intake tube, upper intake, drain the coolant + oil, fuel rail + injectors, lower intake, valve covers, exhaust manifolds, rocker arms, pushrods, and heads. That includes unplugging all the electronics and vacuum lines connected to the intakes and whatnot. As long as you have the tools and a Haynes/Chilton manual, it's not a horribly difficult procedure. You just need to remember how everything goes back together, label your bolts, and properly torque everything back down to spec.

[Mr. Red Pony]

Blown head gasket.

[TheUNZippee!]

Originally Posted by Mr. Red Pony Blown head gasket.

Doink.

[Loki]

Originally Posted by MustangV6Man? Hmm I got a 95 V6, one thats susceptable to abd head gaskets. Now granted, I have no clue if the guy before me ever changed the gasket or whatever, but what can I do to make sure this never happens cheap?

If I remember right, your year is prone to it because the bolts don't as deep into the block as the 96+. If I'm right in thinking that, there's not much you can do..

[Mr. Red Pony]

If you're planning on fixing it, I have better than stock head gaskets for sale never used.

[Mr. Red Pony]

And if the coolant is leaking into the cylinder, which I suspect it is. The o2s on that side are dead too. Ethylene glycol (anti-freeze) is not good for o2s.