Jump to content

Coolant leak


Recommended Posts

I overhauled my L16 ten years ago and have 62K on the rebuild. It has run and does run like a top. Burns no oil or has any leaks anywhere. This summer I saw that my temp gauge was running a little past mid way, so I checked the rad level and it needed about a quart. I put a new rad, Stant cap, hoses and clamps in it about two years, 8K mi ago.


A little later I found the neoprene grommets for the two penetrations in the fire wall for the heater hoses and completely renovated my heater. Heater core was in good shape so I changed the heater hoses and changed out the heater valve with a new one.


I was refilling the rad every once in awhile until it got cold before Christmas. I flushed the rad with heavy duty Prestone junk and filled it with coolant. I looked all over the place to see where the coolant might be going. I couldn't see any drips, drops. I don't have a recovery reservoir, just a hose out of the filler neck. There is never a puddle after I shut it off.


Yesterday I checked all the hoses, they are all soft and new. I have good clamps and checked the connections to the heater in the cab, looked all over the rad for weeping or leaks. There is no coolant in the oil at all. Lately I have had to put a quart in it every other day... my commute is about 22 miles round trip. I can't see where it is coming out or figure out where it might be going, The only weird thing is that when I take the air cleaner cover off there is a frothy oil/water goop coming from the breather hose connected to the valve cover. It's kind of a lot of goo but not a quart. Never seen that before in hundreds of thousands of miles I have driven it.


I had to change out my oil pump last weekend and had the valve cover off. There is no moisture or even any sludge... it is clean as an engine gets... just oil.


When I built the engine I put in new factory water pump, oil pump, etc. I have lost water pumps before and know what they sound like when the bearing start to go... I don't hear any noise and I'm just stumped.


Any ideas where a quart of water is going every 50 miles??? There is no coolant left and I would love to fill it with coolant again before it gets really cold again... it's been in the 40s but woke up to snow this morning... HELP??

Link to comment
  • Replies 6
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

If it's not leaking externally, or into the oil pan, it has to be going out the exhaust. You can have a leak in the intake manifold gasket or a small head gasket leak that lets it through, not enough to put water in the oil. My 720 was like that from the day I got it. But always had one cylinder with cleaner plugs than the others.

Link to comment

Thanks, I think I can see that. I'm not sure though. I know that when I went to pull the head and just do a valve job, the first head bolds in the torques sequence are the two middle ones on the manifold side. The first one I went to remove sheared right off and the one next to it was hell to break loose... it was rusted in the hole. I had to pull the engine at that point so I could take it to the machine shop to have it zapped out. Those two bolts are between the 2nd and 3rd cylinders where there are water jacket holes that leaked past the head gasket which was pretty deteriorated.



If that happened again how does it get into the exhaust?


I'm pretty sure that i never ran it when it was over heated. It never got more that a quart low on water or coolant. The temp gage ran way hotter on a trip to California during the summer.


Are you saying that you ran your 720 just refilling the radiator and letting it leak out? How long did that go on. I don't have a burning desire to pull the head just to replace the gasket right now. What is the down side of running it like that?


I will pull plugs to see what they look like...

Link to comment

My 720 ran that way for 5 years, and darn close to 50,000 miles. God knows how long it had been like that prior to me getting it; it hadn't run in years when I towed it home. I just had to keep an eye on the gauge, it lost close to a GALLON a week. Of course a week for me is 500 miles. It wasn't blowing a lot of steam either. Nothing noticeable, at least. I made the mistake of putting bars-leak in it... that just had the effect of plugging up the radiator and making it run hotter, though it did somewhat slow down the consumption.


It ran that way until it ate or burned a valve.

Link to comment

Sounds Ratsun fo sho. I subscribe to two schools of thought: Fix, repair, maintain, upgrade, so things last... or do nothing, experiment to see how hard you can whip on it as you drive it into the ground!


Yesterday I started the truck and was loading stuff when I noticed big clouds of water vapor separate from the exhaust smoke. I was looking at pictures of the block surface where it mates to the head, because I couldn't figure out how coolant could leak out of the water jacket into the exhaust manifold. Hainz you are saying that the studs or bolts connecting the exhaust/intake mani penetrate into the water jacket in the block?


I'll try to get to it this weekend. I don't want to let it go. I'm having bad thoughts about my little L rusting from the inside out. It has given me such stellar service all these year, I want to make it right.


Thanks for the help guys.

Link to comment

if the intake/exhause is loose. the early L motors have a water passage holes in the head. 2 of them. You will have a water line that goes into the intake near the carb. this healp heat up the carb so it dont ice up in the winter. when the car warms up you will get pressure. alot of pressure. so it will want to push out. Now if the gasket is worn or crack or the intake just loose enough to let water out. but since the 2 inner intake runner are right there they might suck watet into the intake.

If your spark plugs are really clean and white that is another sign of water getting sucked in.


On a cold morning start it up and watch and c right under the intake and exhaust mayb youll see a drop of water/antifreeze.



My L motor my headbolt were getting loose just enough that I was loosing water then found my plugs very clean( it was a rebuilt crate motor) I had never ck the torq on the bolt. My mistake


whn you figure it out make sure to use 50/50 mix as this preservers the timming cover/water pump from cavitation

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.