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TR6 '72 TR6: Oil in Coolant

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Martin Secrest

Senior Member
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Need some opinions. I've noticed oil in the coolant of my '72 TR6, and here's what I know. The leak into the coolant is not horrible but it's definitely there. Have done some very preliminary checks, like a dry compression (forgot to open throttle, oops) and I'm getting ~120 psi at cylinders 2-6, and 140psi at #1. Plugs on cylinders and 2-6 look good, but #1 looks black.

Also, I realize that the radiator cap is rated at 13psi, and it's supposed to be 7. That will be replaced.

How I should continue to scope this out? Hoping for not a head gasket replacement, but the big difference at #1 is concerning. Thanks.

Martin Secrest
Arlington, VA
 
Martin - not good news! But there are a couple angles.

You find oil in the coolant. But is there coolant in the oil? That'll give you some info on whether it's a head crack, or just a leaking gasket.

Give the oil itself, and let us know what you find.
Tom M.
 
Let the car sit over night. Then check the dipstick in the morning. You want the coolant to separate from the oil (if there is indeed coolant in the sump). Coolant on the stick would be less shiny than the oil, and probably a greenish tint (if it's common coolant). Or a greenish/brown tint if there's a lot. Here's a photo that might help:

headgasket-failure-showing-on-dipstick.jpg

One step at a time!
Tom M.
 
Thanks for the pix, that helps.

My car's been already sitting a couple weeks while I do a bunch of winter stuff. Coolant is drained. I checked, and the oil looks/smells normal, like first photo, just a little darker, which reminds me that I need to change it. So it looks like we have a one way transfer, oil>coolant.
 
Great - you saved some time. Coolant is drained, but there's oil in it. But probably no coolant in oil.

Oil into coolant doesn't usually indicate head crack; more like intake manifold gasket, or head gasket. Any smoke in exhaust while driving?
 
Not sure on the smoke in the exhaust. It's not possible to run the car at the moment.
Question: could the 13psi radiator cap be implicated in this? Does an overpressurized cooling system pick up oil? But more concerning is the #1 plug being black, while the others are fine, and the pressure in #1 being 20 lbs. higher than all the others.
 
I'm no expert, but seems that an overpressurized cooling system would push the oil away, not suck it in.

Black plug could be valve problems. In my TR3 I solved that problem by letting SeaFoam soak inside the cylinders, which freed piston rings and valves, bringing compression back in line.

Tom M.
 
unless you drained the coolant into the drain pan you generally use for changing oil. Guess what will float right up to the top?

As far as looking at the oil.....dipstick, if it looks like a "milkshake", coolant has semi-homogenized after being perturbed through the oil pump.
However, you will also see it under oil fill cap (high point) and if you pull the rocker cover.
Oil is higher pressure than coolant (generally) so really anywhere the two passages are close. Had a GM that cracked internally between oil gallery and coolant gallery.
How much oil in coolant? Drop or two, or mop it off the top with a rag?
 
I cleaned the drain pan before draining the coolant into it. I also noticed an oil slick on top of the coolant when I looked into the radiator. No milkshake on the oil cap or dipstick, and the coolant just had a weird kind of brownish green tint to it. It wasn't pure green like it's supposed to be.

I appreciate the help everyone. NutmegCT, regarding the intake manifold gasket, it's rather new, I renewed it when I changed out the exhaust system last year. Hopefully I installed it well, but if this were the problem rather than the head gasket, I'd be very relieved.
 
Martin- you'll probably get other suggestions, so don't rush into anything.

Hopefully others will read this post and give ideas.

Tom M.
 
Don't panic. Milkshake on dipstick may be nothing more than water condensation from running engine while cold. Take a long ride at high speed, then check dipstick after engine cools.
 
So, this thing I thought was 'oil in the coolant' looks to be just the result of years of coolant neglect. LOTS of rust and black slime in the flushes. Finally pulled the block drain plug (duh): totally blocked. Gouged out the grime, it came back and plugged it a subsequent time. Long story short, after many, many flushes, citric, soap, vinegar, citric, more soap (I even used Spray Nine, which worked well) and now some CLR, I am finally approaching something resembling 'clean' on the system. Which means I can finally plumb in my new heater core, the winter project that started this whole thing. These cars are meant to be cared for, knucklehead (me). Especially when they near the half-century mark.
 
Martin - great news that you've taken action and solved the problem.

You wrote: "These cars are meant to be cared for, knucklehead (me). Especially when they near the half-century mark."

That applies to our bodies too.

Tom M.
a/k/a The Ancient One

 
Well it's all back together. New heater core, heater fan fixed, new hoses, fan, belt, water pump and other things. And the block is so clean the coolant's actually green. Crazy. Now on to the clutch master/slave.

 
Keep an eye on that green top radiator hose and it would be a good idea to keep a good spare one in the boot.
 
Poolboy do you mean the main hose(s) at the top of the rad? Why for, do you think? The one I changed out had been on the car for probably 25 years and still looks OK ...
 
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