Morning Guys and Gals.

Haven't been to the Forum lately as life has intruded- as it does all.

I am with a whole day to try and fix an overheating problem with Charlotte (aka "charlie"), our slant 6 powered 'vert. I think it will turn out to be the head gasket, but I wanted second and third opinions before I tear the head off!

Background: So called Super 225, bone stock, 1 barrel (thanks Dan! The Carter works great!). We have been just driving the thing as it sat for decades without. Done the fuel mods, got the timing advanced as far as I can (44 degrees total, no detonation, runs good), just fixing what fails as you put a car back into service after so long sitting up. . .

160 stat with a oversized aluminum radiator and new pump. Has been running at one third the temp gauge for 7-8 months, winter and summer; we have made 300+ mile highway trips with no problems, lots of city driving in Dallas and Austin where she only gets to mid range idling at the lights. Overall, just quit looking at the temp gauge- problem solved.

Flash forward to about 2 months ago- driving highway at 75, been on the road for about 40 minutes, just happened to notice the darned thing was up past the midmark. Pulled over and checked the water- very slightly low but visible. Let her cool, started her up, made our stops, made it back 40 minutes north- running higher but manageable at 60-65 with the heat off the day- back down below 90, that is.

Checked everything you would check- not leaking, not "using" water out of the radiator, no water in oil, did another flush and run through the block, new lower hose that looked like it was collapsing a bit, fresh antifreeze and water, rechecked the timing and reset for advanced, etc.

Now, it starts hard and spits and coughs until it warms up, but it runs cool at idle (1/3rd of temp gauge). Sat at idle for over an hour while I fiddled with the timing and all. You drive it about 10-15 mins though and it starts to get hot- not all at once, but gradually will go to 3/4ths-7/8ths temp gauge before I run out of nerve and stop and let it cool. I smell a strong odor of ethylene glycol on occasion, but it doesn't seem to be losing any coolant out of the system. Do seem to get a bit of excess condensation out of the tailpipe on startup, but does not smell/taste sweet (I tried it). Does seem to dry out when warmed up to operating temp. When hot, I do hear steam expansion "bangs" in the system, but the water level never seems to drop enough to see. Can't smell exhaust in the water myself and no bubbles I can detect. Good flow at idle and with the throttle held down to about 3000 rpm.

Just pulled all the plugs for the second time- hoped to see some rust or something water related- but plugs still seem fine in color and wear except for one- a little discolored is all.

Just did a compression check dry and wet this morning and compared it to the numbers in my ancient Chilton manual- the highest number does not get on the chart after wet test (130 lbs) and the lowest is 115 after wet- was 100 lbs on the dry test. Note that my compression tester is NOT calibrated- just try to go with high to low differences. Not really enough difference high to low to be noteworthy- though the back three cylinders seem to be lower than the front three (118, 115, 125 versus 130, 128, 130 wet.)

My unexpert guess is a slow leak of combustion gasses into the water jacket through the head gasket- just enough of a leak to warm up the coolant beyond what the radiator can cool at speed. I'm guessing that putting this probably un-rebuilt little darling back into full temperature service finally put the head gasket OUT of service. I am hoping that since I don't find water in the oil that there is no crack in the head, piston top or cylinder wall. . .and I am hoping that not enough water enters one or more cylinders as it cools to materially rust the cylinder walls and kill my piston rings off. . .

Please, look at the above reasoning chain and tell me if I might be missing something else to look at.

Also, it would be nice to know just what a Slant 6 ought to have for normal compression pressures minimum and maximum, if anyone knows.
I've used this same compression tester on my 318 and it runs 170's to 180's. 'Course that one has more base compression. . .

Mike

Your compression is a little spread out, but I don't think that it's a problem.

Have you got a steel shim head gasket on this car?

There are some "Shake out" holes that were used to get sand out of the block and head after the casting process. If the head gasket is starting to fail, the coolant can short circuit through a rusty gasket, not flowing all the way to the back of the block before flowing into the head. This will result in high temperatures under load. The smell may be from excessive coolant expansion flowing to your expansion tank, or if such is the case, out the overflow tube.

With the car at idle, you may be flowing enough coolant to allow for some circulation. Out on the road with high load, the smaller coolant flow to the rear of the engine and head would be inadequate to cool the engine.

I'd pull the head and do some snooping.

CJ

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Part of Tyrde-Browne Racing

I know this probably sounds simple but,my 1970 VF coupe i had a couple of years ago was overheating at one stage.Turned out to be the exhaust pipe just as it started going under the car had been squashed almost to half it's size from hitting a bump(it was very low).I fixed that and it didn't overheat.Also,if it has been sitting for a while,some critters might have crawled up your exhaust pipe and built a nest,thus restricting exhaust gasses from escaping.

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DRIVE IT,DON'T HIDE IT

If you want to test to see if you are getting coolant in the combustion chambers, here is a good way.

You will need a radiator pressure tester, can be borrowed from most loan a tool places. Do you use anti-seize on your plugs, if not it would be a good idea to pull them and apply some, as this test will require you to remove them hot. With the plugs in (of course) and the radiator cap loose or off, run the engine till it is up to temp. Shut it down and pull the plugs while still hot. install the radiator pressure tester and pump it up to whatever pis your radiator cap says. Have an assistant crank the engine while the plugs are out and the pressure is on. Any leaks to the combustion chamber will show up as coolant shooting from the affected spark plug hole.

A plugged or semi plugged radiator can cause overheating at speed too.

Is this an air-conditioned car? If so look for derbies between the condenser and the radiator, or anything blocking air in to the front of the car. I once installed a large transmission cooler in front of the radiator on one of my trucks, and saw coolant temps raise 5 to 10 degrees.

I would also test with a known accurate temperature gauge.


TopHat

Ceej, Bucket and Tophat-

Decided to go for it- gotta need a gasket anyways. We are down to the head bolts in about 1.5 hours. Am drinking a beer before performing "surgery"- Daughter assisting! Will let you know what, if anything I find- taking pics as I go.

Thanks Guys.

No guts, no glory, eh what?

Did get the thing pulled down to the gasket- taking pics all the way, will try to post.

See indications that the gasket was failing- paper separating along one edge between the #3 and #4 cylinders, some signs of darkening along the metal toward the water jacket passages. . .

. .and about half the water passage holes either completely or partially blocked in the head by crud. Damn the previous owner for neglect! Heck, I would have been hot too if I was using only half the water flow- but it wasn't until the gasket started leaking combustion gasses into the same slow water flow. Don't know how the thing didn't crack or warp. All valves look good, the heads look fairly clean as to the valves- even see nice ash on them from the lead additive I've been putting in.

The cylinder walls are obviously original size, never been cut- so this thing is on its original unrebuilt motor.

Am putting the head on now, will try to button her up tonight. Let ya all know.

Thanks for the input and support.

Mike

A gasket that has "paper" is not factory and has been replaced. A "factory" gasket is 1 thin piece of metal as far as I know. The felpro type of replacement gasket will drop compression a bit, as it is thicker then a factory style "steel shim" gasket.

TopHat

Good luck on this. I think you are on the right track.
Sam

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It didn't help after all. Got her buttoned up, timing set, valve lash reset, idling smooth- and took her out yesterday and same deal. Runs nice, but after a 10-15 minute highway run it starts to creep up in temperature from 1/3rd of the gauge (160 'stat). Once it starts up past the halfway mark it continues to heat even if you slow down to 20-30 mph. Nice afternoon/evening about 83 degrees F. I let her get nearly to the last tick this time- and once shut off, steam and water out the outflow, temperature of the outside of the radiator about 180+ with another thermometer I have that goes to 220 degrees.

Moved the timing more advanced- up to 15 degrees BTDC- it controls the temperature better- actually will stay at 1/3rd to 1/2 temp gauge and more importantly, it will cool back down from a speed run like it ought to. . .unfortunately it won't idle without a miss and is hard to start cold. I can't hear detonation- but I'm not sure that it isn't occuring silently. No indication of detonation on the plugs either- nice clean light brown, no overheated ceramic or welded looking electrodes. . .Ran her at 44 degrees total advance (preset, mechanical, vacuum) for 8 months and she did great- got that idea from Mopar Action Mag and Erhenberg article from last year. . .dunno.

Now, what about a crack in the head? I wish I had taken it to be Magnafluxed I had it off. Did closely inspect the thing, but. . .sigh.

Before I go to the time and expense of disassembly (again!), will try to see if combustion gases are getting into the radiator water a 'la TopHat's suggestion and procedure. Right now, going back to re-check the simplest stuff- good pump flow, clear water, clear radiator, flush and fill, etc.

Quick answer to a few other suggestions: no, no A/C so no condenser (one day!); exhaust is 1 7/8 to 2.5 from the outlet point all the way back and new, not crushed; there Was crud inside the block when I replaced the freeze plugs, but we dug all we could out and then flushed- and the damned thing did run cool for over 8 months. . .?

Keep those thoughts and suggestions coming! Appreciate the help.

Mike

Have you tested the thermostat in boiling water?

Both for when it opens and how far it opens...

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

If you had coolant getting into the combustion chamber, you should have seen one or more cylinders with a steam cleaned piston crown and combustion chamber. Even with a tiny crack that barely causes trouble, there will be a clean spot along the crack. This would jump out at you even if you are not looking for it. You could pull the plugs and look at them and see the same thing.

I second checking the thermostat.

Moving the timing seems to have helped some. Are you absolutely sure that the TDC mark on the balancer is REALLY TDC? Search my posts on how to make a piston stop for real cheep. Retarded timing will make a car run hot. Balancers can slip, or be marked wrong from manufacture.

I doubt you have a cracked head. I once ran a slant hot to the point that it burnt all 6 exhaust valves. Sounded like it had no plugs in it when you turned it over. Towed it home, Pulled the head and spent 3 evenings with a power drill and valve lapping compound, put it back together and it ran decent on all 6. Burnt a good amount of oil due to the rings being shot, and no valve guide seals at all.

Rule 1 is ALWAYS rule out the easiest least expensive things first. You will get it figured out.

TopHat

I wish I could get pictures on here easier- got some of the head downloaded at forabodies.com- no steam cleaning in any of the pics of the inside of the head or of the pistons in the block.

I was running a 160 degree thermostat- took it out for the flush I did today. Likewise, went and borrowed a system pressure tester and hooked it up- steady as a rock pressurized, even when the engine was running and tried and tried to get it to shake the needle with the motor at normal temperatures and RPM up to 4000-5000 and held. Nothing. If a crack were there and opened with the heat, I should have seen something like a pulsing into the water and shaking that needle. Didn't even pressurize it above the 15-17 lb point. So, the head and gasket seem good.

Drove the borrowed tool back to the AutoZone- ran on tap water only, got no hotter than 1/3rd temp gauge. Gotta be the 'stat- it isn't even in there any more!

Then, took it out and ran it on the highway-65-70 plus for 5-8 miles- temp crept up to 1 tick past the halfway mark- still getting hotter than it should. . .

Pulled over for gas, restarted it- needle 2/3rds with the stop, then as the water circulated, dropped right back down to 1/3rd. However, while driving now at 50-60, needle started its creep back to halfway. . .about a 5 mile drive back to the house.

Driving me to drinking, it is- and now I am out of beer!

Then, it dawned on me- TWO sources of heat being inputted into that radiator- the engine and the automatic transmission.

Just how hot does the transmission operate normally? Just pulled the dipstick for the tranny- the stick is plenty hot, but the oil is still clear red and didn't cook my fingers. . .but I got thick hide there too.

More food for thought. . .

Your test with the pressure tester is correct, should not have a head or gasket problem.

Remember that plain water is a more effective coolant then anti-freeze mix.

No stat at all can flow the coolant through the rad to fast to allow it to completely cool. Take an old stat and cut the loop that holds it all together on both sides to allow the guts to fall out. You should have just a plate with a hole in it. The plate will restrict the flow similar to an open stat.

I am still thinking that your timing could be the issue. Verifying the mark on the balancer is fairly easy with a piston stop, especially if you have a bolt in your balancer, still not hard if you don't

Here is a link to how to check TDC:
http://slantsix.org/forum/viewtopic.php ... iston+stop

In my post is a link to my post on FABO on how to make a piston stop. Depending on what you have laying around it should cost you between $0 and $6 to make. Balancers can slip, be marked wrong, or be the wrong one for the engine.

The automatic trans should not be causing your issue. The truck mentioned in my first reply to you, with the big cooler (half the size of a D150 rad) has a trans temp gauge on it. With a 3000# trailer, in 95 degree weather the trans runs about 130 to 140 degrees. The truck is a 318 / 999a (904 lockup). For your trans to be causing your problem the fluid would be burnt black and probably slipping or not shifting.


TopHat