What's a Blown Head Gasket?

equeen · Sep 25, 2012

Years ago had oil in radiator of an 8N. Took tractor to mechanic who repaired - said cause was a blown head gasket.

Have a '50 8N with oil in radiator and low compression on cyls 2 & 3. Decided to tinker myself.

Photo (I hope) shows gasket still on head. Bits left on block. I don't see anything "blown".

What am I missing?

If gasket wasn't "blown", then what are other possibilities for oil in water?

Thanks.

old · Sep 25, 2012

Well if you had posted a picture of the gasket that might have helps. Can not see any thing wrong with the head or any leaks but you can not always see a problem like that on the head. Do make sure the head is flat and not warped. Low compression on 2 and 3 does sound like a blown head gasket and yes they can blow and you not see much unless your 100% sure of what your looking for

souNdguy · Sep 25, 2012

2 could be dumping in 1 and 3 in 4.. or both into water jacket.

combustion byproducts blowing into water jacket can give it an oily sheen.

remember.. comp pressure inthe cyl is going to be big double digits... water pressure is gonna be 4 psi.. and oil pressure somewher eunder 45 psi..e tc..

if it is truley oil in water.. cracked block..

thommoos · Sep 25, 2012

Crank in the head or warped, need to get it magnafluxed and checked.

equeen · Sep 25, 2012

The gasket is right there on the head in the posted photo, just as it was removed from the block.

Will clean up the gasket and post a photo of it alone.

Thanks.

JMOR · Sep 25, 2012

(quoted from post at 11:53:40 09/25/12) Years ago had oil in radiator of an 8N. Took tractor to mechanic who repaired - said cause was a blown head gasket.

Have a '50 8N with oil in radiator and low compression on cyls 2 & 3. Decided to tinker myself.

Photo (I hope) shows gasket still on head. Bits left on block. I don't see anything "blown".

What am I missing?

If gasket wasn't "blown", then what are other possibilities for oil in water?

Thanks.

This is only spot that I see that might look suspicious. Need to look at other side of gasket, too. Don't see any evidence of steam cleaning in combustion chamber, which suggest to me that you have no water to cylinder leak.....were you needing to add coolant often? No? Then probably no leak. I will never understand why people just "have to" jerk an engine apart BEFORE diagnostics! Just waste of time/money & destroys evidence that might help diagnose the problem, if one exists. There is no direct path for oil to be pushed into the water jacket in this engine.......no oil passages in head or head to block interface/gasket. IF, if you had a compromised head gasket connecting cylinder to water jacket, then at best some combustion products could find their way into the radiator, but that would NOT be a lot of oil & if observant, one would see the bubbles in the radiator. IF you had a cracked block between water jacket & crankcase, that would yield water in oil pan, not oil in radiator. What you probably HAD, was a perfectly well operating engine, with an oil-sheen in radiator resulting from lubricants in coolant.......probably only thousandths of an inch thick, on top of water/anti-freeze mix.....nothing to be concerned about. If you are good & lucky, I will be as good as it WAS before when you put it all back together.

teddy52food · Sep 25, 2012

That spot goes to a head bolt, not the water jacket. Low compression could be valves too.

JMOR · Sep 25, 2012

(quoted from post at 13:16:28 09/25/12) That spot goes to a head bolt, not the water jacket. Low compression could be valves too.

......nah! Coolant hole. But even if it were a bolt hole, the bolt hole goes into water jacket, too.

equeen · Sep 25, 2012

Appreciate all comments.

Soundguy, I didn't run the tractor except for a spin around the man's yard. However, I saw the oil saturated around the radiator fill neck "cushion material" and the oil in radiator. After removing the head, I saw the oil in the water jacket of the head and engine. Nope, not just a sheen.

May be a mistake since probable block problem; but head is at engine machine shop and quick check suggests will need to shave about 0.015 off head around cyl 1 & 4 outside.

I am going to have the block magnafluxed, or whatever. Cost is reasonable for me to at least know.

I'm guessing that it would depend upon location and size of crack, if it exists. But, any welding options for a block cracked in this probable manner. (No visible external cracks or cracks at top of block.)

Thanks.

equeen · Sep 25, 2012

Photo of top of engine. No visible problem - to my eye.

How about the eyes of y'all?

JMOR · Sep 25, 2012

Unless you have done an awful lot of cleaning, someone has been it there very recently!
I don't think you have/had a problem. Sorry.

souNdguy · Sep 25, 2012

if it's at the machine shop and they are crack checking it.. let them advise you.

SOME cracks can be repaired.

old · Sep 25, 2012

Laying as it was I could not see what was what and of course even a picture is hard to see and know for sure.

equeen · Sep 25, 2012

Head was warped. Being checked for cracks and machined if okay.

I just don't believe that the gasket was "blown".

Some folks have questioned if oil was just a film on water. I now think that it may have been and I have no clue as to when the coolant was last changed. Have flushed the block with hot water and approx tablespoon of oil came out. Rest was water. However, more flushing to do - and tractor is not parked in such a way that all liquid comes out.

Tomorrow's a new day. Hope to re-install head and radiator and learn some more.

ASEguy · Sep 26, 2012

I don't see anything conclusive. Low compression on cylinders 2 and 3 could be a head, head gasket or block issue, but it's usually interpreted through the compression readings and not "low compression on cylinders 2 and 3". Compression testing is usually done dry cranking then wet cranking, and if that's not conclusive, running compression on the affected cylinder(s). Posting the numbers for all cylinders would be a big help. Also, with any gasket failure BOTH sealing surfaces must be suspect until proven acceptable. It doesn't make sense to assume one surface is acceptable and one may be defective. I have found low spots on blocks with a straightedge and cracks with dye penetrant test kits which were not visible to the naked eye. Hope this helps. Gerard

NOXJohn · Sep 26, 2012

Something is definitely wrong. I have never seen a block that clean for an engine that has ran for any length of time. The pistons and valves look like they have just been wire brushed. How can there not be a carbon buildup on the pistons and valves? If this tractor has been running for years and the insides look like the picture then water is getting into the combustion chamber some way because that is the only way I can see for it to be that clean.

old · Sep 26, 2012

A warped head will cause a blown head gasket in a way you may not see unless you ran the engine for many hours so that it would be slowly eaten away

sgtbull · Sep 28, 2012

Just a word of advice... It appears that you have typical domed head pistons. After you have the head machined, make sure that you still have
adequate clearance between the piston and head. This may not be the first time the head was shaved, and if too much is taken off, the piston will strike the head. If it does, you can relieve the head a bit with a dremel tool, but you might be best to look for a new head if the interference is too much.

Britcheflee · Sep 28, 2012

(quoted from post at 11:46:31 09/25/12) Photo of top of engine. No visible problem - to my eye.

How about the eyes of y'all?

That has to have been cleaned - however, not completely - I would carefully scrape the remainder of the head gasket stuck to the block before installing the new gasket - I used one of those sharp blades in a holder to remove paint from glass - just dont gouge the block.
Looks like they used one of those scrubby things on a drill to clean it up - will take most off and polish but will not remove the really stuck on stuff.

Lee

equeen · Sep 28, 2012

Thanks, Sgtbull.

The head has been shaved .020, caution given by engine/machine shop and instructions as to what to try if head wobbled when lying loosely on the block. Didn't have a problem.

Re-installed on engine and tractor runs fine. Replacing trans/hdy/diff fluid today, then hope to work out the tractor for about an hour.

equeen · Sep 28, 2012

I cleaned it before photo. Wasn't terribly dirty; cleaned easily.

equeen · Sep 28, 2012

Thanks, Gerard

Hoping that the old tractor will perform small garden work for a few more year without major engine rebuild. I am concerned regarding cyl 2.

Current approx dry compression readings - this morning with cold tractor:
1-107
2-97
3-112
4-112

This is a major improvement on all cylinders after head shaved and new gasket. I'm going to work it for an hour or so. Also, very little smoke this AM from cold tractor exhaust.

equeen · Sep 28, 2012

Yep, used one of those scrubby things on a drill. Used a razor-type blade to clean gasket areas before re-installing head.

equeen · Sep 28, 2012

Head was checked by shop for cracks. None.

Decision NOT to rebuild engine at this time - thus engine has not seen the shop and has not been checked for cracks.

Will be watching water carefully as I run the tractor. Just a very light sheen on the water in radiator now - but probably a carry-over from old oil in water jacket. (Had radiator cleaned.)

equeen · Sep 28, 2012

Head no longer warped. Will be running tractor and observing "things".

R Geiger · Sep 28, 2012

(quoted from post at 00:41:33 09/29/12) Head no longer warped. Will be running tractor and observing "things".

Don't forget to retorque the head bolts.

souNdguy · Sep 28, 2012

flush it to get oil out.. then run with straight water a few days.. water is easier on bearings than coolant.

once you are sure of no leaks.. add antifreeze.. if you are in freezingf area.. drain at night.. etc..

Hobo,NC · Sep 29, 2012

Look'n at your pix Yer head gasket was not blown... I have no doubt it leaked but see no evidence it was blown...

If it were blown it would be extremely EZ to find,,, a visual test like I see water in the hole no compression test needed....

It LEAKED,,, My bet at the upper end are at the highest compression point that is why a compression test are a leak down test may have never found it.... The lost would have been minimal (if at all) you would have considered the lost to be normal.... It would not have been a continuous leak (blown) it would only leak at TDC (highest point of compression) and then only for a nano second.... A pressure test may have been you only hope to nail it before you went guessing.... If you had continued to run it it would have blown,,,, the leakage would have burnt out the firing ring (seal)...

Larry Barnes · Nov 20, 2012

I am replacing my blown head gasket. The head has been shaved before. It"s got a .007 warp now. Do I need to shave again? And what is minimum tolerance to leave so the pistons don"t hit?

Thanks, Larry

What's a Blown Head Gasket?

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