Antifreeze coolant Leakage M38

[BrianR]

l have leaking coolant dripping out of the rear exhaust mount after 8 litres of installing antifreeze. it stops leaking at a lower level when reached. l just reassembled the engine and do not know what is the cause or fix.
Hoping someone can help. M38
Regards
Brian.

[skyjeep50]

I just went through this with my M38. Possible sources would be a cracked block or hole in the block somewhere (which I had) or a leaking head gasket (which I had), a defective head gasket (which I had) or a warped head or block (I dodged that bullet). I used Permatex spray copper sealant, which is supposed to be a high quality head gasket sealant, but found that unless the engine is run and the block isn't heated up, the sealant doesn't seal completely between the metal face of the head gasket and the block. That little fact does not appear in the instructions for the product or anywhere else I researched! Felpro also recommends a "Brush Tack" sealant which may seal better from the get go. You are looking for a pathway from the coolant galleries into the cylinders or exhaust ports. Be sure to check to make sure the engine oil is not contaminated with coolant - crack the oil drain plug and see if coolant drains out - water is heavier than oil and will be on the bottom of the oil pan. If so, you've got to clean out the engine - you don't want coolant circulating with the oil - bye, bye bearings! Perform a head leakdown test - I attached a brass hose fitting to the coolant plug on the back of the head, a "T" to a pressure gauge and my compressor, dialed down the pressure regulator to less than 10 psi and gently pressurized the coolant system and watched the pressure drop over time. The coolant system operates at about 4.5 psi normally. If the system doesn't hold pressure easily, you've got a hole or breach somewhere. My system had a slight drop until I ran the engine, when the head gasket sealed, no more problems. You can use soapy water around the head to block junction (brush it on with a small brush) to check for leaks there, watch for bubbles. Good luck!
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1951 M38

[BrianR]

Hello Skyjeep 50:

l drained some oil from oil pan and saw no signs of water or antifreeze. lYou mentioned that you found a hole in your block and had a leaking head gasket, were was the hole in your block? My engine was in a machine shop and was magnaflux , checked for cracks first before furthur work was done. l am not expecting to find a problem with a cracked block unless l enstalled 0ne of the cylinder head studs and overtorqued the corner one to much and it cracked the block at the #4 exhaust. l will do the pressure test first, as you suggested and let you know results. lf the pressure test holds at 4.5, would this indicate the head gasket is sealing properly and cause of leak is a crack in the exhaust port/ chamber?

Regards
Brian.

[skyjeep50]

My hole in the block was from a botched repair - I asked a machinist to put a helicoil in one of the stud holes (where I messed up the threads) and he accidentally punched a hole through the block at the base of stud hole. He didn't see the damage but I certainly found it later! The original engine in my M38 had a cracked block from another botched repair by the PO but that crack was easy to see - across a coolant gallery from a stud hole to a cylinder wall. If your engine has been checked for cracks, the problem may lay with proper sealing of the head. What type of head gasket and gasket sealant are you using?
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1951 M38

[BrianR]

Skyjeep 50

l purchased my Headgasket from Carquest and l did not use any sealant when l installed. l was careful not to install gasket backwards and torque properly. The gasket Manufacture is Vector and no sealant is provided or required by Vector when the gasket is installed. Should l remove the head and take a closer look, what do you think?

Regards
Brian.

[skyjeep50]

Does your gasket have a fiber side and a metal side? The Felpro gasket I used has that design and instructions from the Felpro website call for some type of gasket sealer for the metal side - either a Permatex brush tack or copper spray tack sealant. The fiber side needs no sealant. There were no instructions packed with the gasket. The metal (gasket) to metal (block) interface will not seal coolant under pressure. Especially in that the coolant galleries are so close to the cylinder bores. That is most likely where your leak is.
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1951 M38

[BrianR]

Skyjeep 50
l do not remember whether my gasket is all fiber or a combination fiber/metal. l understand what you are saying about the sealant needed for metal to metal contact. Tomorrow l guess l will pull the head off and take a closer look, keep you posted.

Regards.

[skyjeep50]

When you reinstall the head make sure you follow the instructions in TM9-1804A M38 Engine and Clutch p. 94 and 95 (see "Downloads" section of this website) for proper tightening sequence and torque specs. After running the engine and bringing it to proper operating temp, shut down and recheck torque with the engine warm.
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1951 M38

[BrianR]

Removed the cylinder head today and found antifreeze in #1 cylinder , #2 cylinder and residue everwhere else. exhaust valve was open, which probably explains why the coolant was dripping out the exhaust port. The Vector brand cylinder head gasket that l had put on was vinyl and no sealant was used. Nor was it mentioned in the instructions.
Should l have applied sealant and how do you install onto the Headgasket?
Was the lack of sealant on gasket the cause of the coolant leakage?

Regards
Brian

[wesk]

There are several head gaskets on the market and several different Manufacturer Preferred installation methods. Some get no sealant and some do. The only sure fire way to get it right is to discuss the specific head gasket part number you have with that specific gasket's manufacturer. Do not rely on any advice offered on these boards and from nearby friends that does not ID the exact part number and manufacturer of the gasket they are giving advice on and do not indicate that they first obtained the manufacturer's directions.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

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