If you are actually losing coolant, and you don't have any signs associated with a BHG (white gunk under oil fill cap, white smoke, sweet smelling exhaust, etc.), then you have a leak somewhere, just keep looking. I am assuming you don't see any puddles under the car overnight. Check the head/block joint on the exhaust side of #3 and #4 cylinders for a coolant leak from a leaking head gasket. A bad radiator cap will typically overfill your coolant expansion tank. Don't assume because you have a new cap it is good - get it tested to make sure it holds the correct pressure if you suspect that may be your problem.

David
white 89NA

 

Ok, I will check the exhaust side...is that a common place for a coolant leak on 4a's? it would make sense that there is no sign of it if it's by the exhaust. I will keep looking, thanks..

If you are actually losing coolant, and you don't have any signs associated with a BHG (white gunk under oil fill cap, white smoke, sweet smelling exhaust, etc.), then you have a leak somewhere, just keep looking. I am assuming you don't see any puddles under the car overnight. Check the head/block joint on the exhaust side of #3 and #4 cylinders for a coolant leak from a leaking head gasket. A bad radiator cap will typically overfill your coolant expansion tank. Don't assume because you have a new cap it is good - get it tested to make sure it holds the correct pressure if you suspect that may be your problem.

David
white 89NA

 

OH, another thing that I find very odd....is that the system appears to be holding pressure while the car is running, in previous leak situations I've encountered with other cars, the cooling system generally will not hold pressure due to the leak. Also, how long is the system generally pressurized after the car is shut off? I know they cool pretty quickly from my experiences, but I'm not sure how long when the engine is hot that the system will keep the pressure.... I went out about 10 minutes after shutting the car off, and there was only a little bit of pressure left in the system when I opened the cap...

Eric

If you are actually losing coolant, and you don't have any signs associated with a BHG (white gunk under oil fill cap, white smoke, sweet smelling exhaust, etc.), then you have a leak somewhere, just keep looking. I am assuming you don't see any puddles under the car overnight. Check the head/block joint on the exhaust side of #3 and #4 cylinders for a coolant leak from a leaking head gasket. A bad radiator cap will typically overfill your coolant expansion tank. Don't assume because you have a new cap it is good - get it tested to make sure it holds the correct pressure if you suspect that may be your problem.

David
white 89NA

 

I had a similar problem with my 87. It was constantly losing coolant and no leaks to be found. The engine still ran great, pulled hard, etc.. so I didn't think it was the HG at first either. Replaced everything, still losing coolant.

It was a very small leak in the HG. Exhaust gasses were being pushed into the coolant, but coolant was not making it into the cylinders. The exhaust gasses would start to displace the coolant and it would end up filling the overflow tank and dumping on the ground while driving, but when stopped, it wasn't noticeable.

Replaced the HG, problem went away.

 

that's annoying......it looks like a PITA to pull the head on this thing.....how difficult is it? I assume that I can do it with the engine in the car?

Eric

 

yeah, I'd check your coolant overflow bottle. See if it's comin out of there.

 

the overflow bottle never seems to get empty.....I think it's pointing to exactly to a small head gasket leak...there is no water coming from anywhere on the engine, it's dry....I climbed under the car and there is no leaks anywhere else. so that is the only option at this point I think....

Eric

yeah, I'd check your coolant overflow bottle. See if it's comin out of there.

 

Before you pull the head, check, or have someone check, for hydrocarbons in the cooling system. If you have a small exhaust leak from the head into the coolant, this will pressurize your system, but will also put hydrocarbons into the system. If your coolant bottle is filling to the point of overflowing, it is either a bad radiator cap or a BHG.

David

 

well...I did notice today when letting it run, after getting all of the air out of the system, it still bubbles randomly.....pretty often actually....and it smells like exhaust.....I'm going to just do it, and replace any other hoses while I"ve got it apart..... I've never done it, but I think a couple of hours should be good to get it off and a couple to get it back on....used to be able to do the HG on my 85 supra in like 2 hours lol

 

I had the unfortunate luck on two engines. It was caused by a blown head gasket below cylinder #4. Coolant would leak out only after the engine got hot after running for an extended period to time. In my case it was about 40 minutes of freeway driving and less time if the temperature was above 80 degrees. The tear in the head gasket lead from the #4 cylinder to the outside of the engine, missing the oil passage. No coolant was detected mixed with the engine oil.

A small amount of coolant would weep out of the engine but would evaporate on the hot engine and there was never enough that it would drip on the ground. There was always a lingering, somewhat sweet smell of burnt coolant which I could not track down.

When the engine got hot enough, the hot gases would blow into the coolant passage and over-pressurize the cooling system. The hot pressurized gasses would eventually blow past the radiator cap and into the overflow bottle as steam. The steam would somewhat filled the bottle above the normal fluid level but the majority of the steam and suspended coolant would get discharged out of the cooltant bottle overflow tube. Initially it was hard for me to believe what was happening because I did not observe any wetness along the inner walls of the engine bay below the cooltant bottle overflow tube. I confirmed what was happening by making a paper towel tube and zip-tying it around the end of the overflow tube. The coolant was discharging out of the tube and some landed on the muffler which was also contributing to the burnt coolant smell. In both cases this situation only occurred while I was driving. It would not happen when I tried idling and reving the engine in my driveway or when I drove the car around the neighborhood at residential speeds.

It has happened to me twice on stock original engines. I have read of only one other incident so it could be very rare.

A long time ago, someone had a similar problem and it turned out to be a hairline crack in the cylinderhead to one of the coolant passages. When the engine got hot, the crack would widen and pressurize the cooling system. The crack did not leak coolant when the engine was cold and the compression tested within specs.

 

WOW!!!! that is exactly what is going on, pretty crazy....well....I ordered the parts, gonna tear it apart tomorrow, take the head down to the shop and have them mill it, and put it back together.....hell, if I'm going to mill the head, I midas well mill it enough to up the compression....it's a stock na motor with hks cams....how much should I have taken off the head, I already have to run premium because the hks cams doesn't like timing below 15 degrees....so premium it is....so stock they are at 9.5:1? How much would I have to take off of it to get it up to maybe 9.9 or 9.8:1?

Eric

I had the unfortunate luck on two engines. It was caused by a blown head gasket below cylinder #4. Coolant would leak out only after the engine got hot after running for an extended period to time. In my case it was about 40 minutes of freeway driving and less time if the temperature was above 80 degrees. The tear in the head gasket lead from the #4 cylinder to the outside of the engine, missing the oil passage. No coolant was detected mixed with the engine oil.

A small amount of coolant would weep out of the engine but would evaporate on the hot engine and there was never enough that it would drip on the ground. There was always a lingering, somewhat sweet smell of burnt coolant which I could not track down.

When the engine got hot enough, the hot gases would blow into the coolant passage and over-pressurize the cooling system. The hot pressurized gasses would eventually blow past the radiator cap and into the overflow bottle as steam. The steam would somewhat filled the bottle above the normal fluid level but the majority of the steam and suspended coolant would get discharged out of the cooltant bottle overflow tube. Initially it was hard for me to believe what was happening because I did not observe any wetness along the inner walls of the engine bay below the cooltant bottle overflow tube. I confirmed what was happening by making a paper towel tube and zip-tying it around the end of the overflow tube. The coolant was discharging out of the tube and some landed on the muffler which was also contributing to the burnt coolant smell. In both cases this situation only occurred while I was driving. It would not happen when I tried idling and reving the engine in my driveway or when I drove the car around the neighborhood at residential speeds.

It has happened to me twice on stock original engines. I have read of only one other incident so it could be very rare.

A long time ago, someone had a similar problem and it turned out to be a hairline crack in the cylinderhead to one of the coolant passages. When the engine got hot, the crack would widen and pressurize the cooling system. The crack did not leak coolant when the engine was cold and the compression tested within specs.

 

I forgot to mention that a board member reported that he had a leak in one the coolant hoses where it fits onto the radiator. Same type of situation. When the engine was operating at highway speeds it created enough pressure in the cooling system to blow coolant out pass the clamp. Before you diassemble the engine, check all the coolant hoses and fitting for leaks that may be heppening when the engine is operating at higher rpms. There is also a weep hole underneath the water pump shaft that starts to leak when the water pump bearing begins to fail.

 

yea, I checked all of that multiple times no, there is no sign of any leaks up front at all....there is no signs of any leaks anywhere except around the overflow bottle....and that's from it boiling over into it when the temp started to climb when it was empty...

I forgot to mention that a board member reported that he had a leak in one the coolant hoses where it fits onto the radiator. Same type of situation. When the engine was operating at highway speeds it created enough pressure in the cooling system to blow coolant out pass the clamp. Before you diassemble the engine, check all the coolant hoses and fitting for leaks that may be heppening when the engine is operating at higher rpms. There is also a weep hole underneath the water pump shaft that starts to leak when the water pump bearing begins to fail.

 

Have you bled the cooling system?

Is the overflow bottle cap cracked - and if not, is it installed properly?

See the threads on bleeding the system and repeat oveheating in the MkI FAQ.

 

I have bled the system, a couple of times....my overflow bottle has never had a cap on it, the tube goes directly into the bottle and had a little rubber stopper on it....it has worked ok all along....

Have you bled the cooling system?

Is the overflow bottle cap cracked - and if not, is it installed properly?

See the threads on bleeding the system and repeat oveheating in the MkI FAQ.

 

before I'd pull the head, I'd go up to napa or wherever and buy the stuff that you can test the coolant with for hydrocarbon/combustion gases. Its a blue liquid, you take some coolant and mix it with the stuff, it if stays blue, good, if it goes yellow, bad.

and dont buy the whole kit, just get the 'refill' bottle, its like 8 bucks or so

 

that sounds like a good idea.....at this point I almost hope that it's the head gasket....cause I'm out of ideas if that's not it lol

 

Well,

I went to NAPA today and got some of the blue block tester fluid. Started the car, let it get warm, sampled some of the radiator fluid and put it in the cup with the block tester and.......it turned blue green color. but more green than blue...so it looks like I've got a dead HG.....Thanks for all of the help and ideas on figuring out what was going on.

Eric
White 87

 

Well, it's almost apart.....for the first time doing it, I'm down to the head bolts and at about 2.5 hours worth of work, not too bad. I think putting it back together is going to be another story lol....I will let everyone know what I find when I get the head off finally.....in a bit I have to go to the parts store to get a damn 12 point socket to get the bolts off......as all of mine are 6 point...lol


Eric

white 87 - head gasket in progress

 

Well....the head is off, found where the head gasket was messed up.....

I have pictures but I have no place to put them, so I will best describe what I discovered.

Basically if your looking at the engine from the front of the engine, the cam gears etc, what I found was

on #4 on the far right corner of the cylinder it ws badly deteriorated, to the point where it was cracked just on the outside of the combustion ring. the ring was pushed out to the point where it was no longer circular in that area, it was pretty much flat. This happened to be right near a water jacket...so there was my problem. If anyone wants to host any pictures for me so they can see exactly what I'm talking about, feel free to send me a message..

Eric

 

When I get home I will post the picture of the head gasket that used to be on my engine. I bet it will look almost identical.

 

That would be interesting......

When I get home I will post the picture of the head gasket that used to be on my engine. I bet it will look almost identical.

 

Very interesting.. I've had some of those same symptems. Got a 85 from a friend that the wife ran it hot, blew the gasket and I picked it up. Did a headjob with another head, ported it cut the seats and put everything back together and same thing..
Lots of girgling until system bled out but can't seem to find the leak also. After reading the Valve adjusting threads, decided to do mine and while looking down near the exhaust cam (cyl#2) I noticed that when I put the headbolt back in the washer must have caught on some metal flashing and laid up next to the bolt and never got torqued down under the bolt.
Well, it's a crap-shoot anyhow but I just pulled the bolt out and reinstalled the bolt.
I only had about 30 miles on the headjob so we'll see if it stil leaks or has the same problems that you state.
I just wonder if just THAT bolt would cause a pressure leak just because of 'no washer' under the head?
What do you kids think? IT still got torqued to 43-45lbs..
But Even though, It seems that I can ALWAYS add a quart or so
New gasket, New pump, Good hoses, modded themostat..
Just won't know until I get the valves adjusted correctly and everything back together

 

The blown head gasket on top and the replacement below

 

yup, exact same place....I wonder what causes that.

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