Overheat coolant - SD25 D21 1987 Nissan

[philip]

If I read that right, Philip, you are suggesting that there is a combustion gas leak into the cooling system, one that the previous (diesel) fluid test didn't catch.

Two common developments will result in cooling system pressure overcoming the pressure cap:

1: Coolant becomes heated sufficient to boil (for any reason) ... cap pressure is exceeded ... coolant is forced overboard. Thermal knocks are often heard and felt on the radiator core while the engine cools off.

2: Combustion gasses raise coolant pressure sufficient to overcome the pressure cap resulting in coolant and gases being forced overboard. This second condition can occur without overheating the coolant.

[after oil]

3: The water pump is sound and the drive belt properly tensioned.

you mentioned earlier that i would hear the belt slip from the alternator pulley. i dont hear any slipping.

after oil wrote:
Whats it doing you may ask? when the engine is warm, (but off of course) it spins a little when i spin it. engine cold: i can turn it, but theres drag, so it doesnt spin. it turns freely from the pulley. (ie i can turn the fan but not the pulley)

Normal.

normal... good

1: Coolant becomes heated sufficient to boil (for any reason) ... cap pressure is exceeded ... coolant is forced overboard. Thermal knocks are often heard and felt on the radiator core while the engine cools off.

2: Combustion gasses raise coolant pressure sufficient to overcome the pressure cap resulting in coolant and gases being forced overboard. This second condition can occur without overheating the coolant.

i dont hear or feel thermal knocks.

so is it #2 then?
is my head cracked?
now what?

[after oil]

Is this water pump good for my '87 too?

[asavage]

I need a better pic of your existing water pump before I can comment on whether the 720 version will fit. I also want a good pic of your thermostat housing.

Retorqueing the head after it begins leaking (on a diesel) is useless. The portion of the gasket where it might be leaking would already be damaged; adding clamp force would not help.

The SD head is an easy one to R&R, if that's any consolation.

[philip]

is this water pump good for my '87 too?

THIS is the ONLY water pump manufacturer I would trust ... "(N)" brand. If the eBay part is GMB brand .... PASS on it.

SD four cylinder pump castings are the same ... but for the GMB pump that needs two bolts to be 10mm longer.

[after oil]

I need a better pic of your existing water pump before I can comment on whether the 720 version will fit. I also want a good pic of your thermostat housing.

will do tomorrow morning

The SD head is an easy one to R&R, if that's any consolation.

so i dont need to replace it ?(if thats the problem)

[REDNECK]

dude.... nissan pt# 21010-10G25, changes to 21010-10GY6 and costs $81.01 CAD. the u-hose, pt# b1069-61500 costs $18.53 CAD. all available at your local authorized dealer.

[asavage]

The SD head is an easy one to R&R, if that's any consolation.

so i dont need to replace it ?(if thats the problem)

What I mean is that it's relatively easy to remove and replace it. If the leakage is at the head gasket interface, the gasket is cheap and the job is not all that bad. Remove the intake/exhaust manifolds, thermostat housing (drain coolant), IP lines, unplug the GP bus, unbolt the PS pump and move it aside, valve cover, rocker shaft assy (8 bolts), head bolts. There aren't a lot of heads that are easier to remove than the SD's.

I was not implying that the head could not be bad, or that the head would be easy/cheap to repair or replace. I am thinking positive here.

So far, with what you've tested, checked, and replaced, with the exception of the negative combustion gasses test, I think it's possible that you might have a combustion chamber or gasket leak. I don't pull heads lightly though, and that's why I recommended upthread that you pressurize the cooling system with a warm engine and engine not running, and see if it holds pressure. If not, pull Glow Plugs, tap starter and see if water comes out of a hole.

Requires a 12mm deep socket, a 12mm wrench, and a cooling system pressure tester rig -- which might be able to be rented from a FLAPS. Still cheaper than pulling the head and replacing the head gasket.

[after oil]

that pressure test was done. it passed. still, it was the rad guy who did it, he still guessed head gasket.

how bout somehow attaching a pressure gauge to a coolant line to see what kind of pressure is building?

[REDNECK]

why not just put the radiator tester on the truck and start up and see what pressure it builds in the rad as it warms up? If....IF the head is cracked the only time it might leak is when it is warm....at which time it'll start to build pressure...note the temp. if it builds right away(cold) ,.....usually there is white smoke.........just a note...how many psi is the cap you currently have?

[asavage]

why not just put the rad tester on the truck and starter up and see what it builds in the rad?

We already know that pressure builds when the engine is running -- the cap's pressure spring lets gasses & fluid into the reservoir. Having a gauge tell you the system is going above 13 PSI isn't going to help, and you still won't know anything more than you do now.

Which is why I specified to test on a warm engine, with the engine OFF: no more heat is being produced so a hot spot or flow issue is of no consequence during the testing.

==========

I did once have a Subaru in that would ONLY overheat and dump fluid after it was warmed up and then only if you pushed it a little, like up a hill. Then it would overheat and bubble and steam and keep doing that until you shut it off, no matter what.

It passed the CO-in-coolant test (when it wasn't overheating; you couldnt sniff it when it was) and the cooling system pressure test too. We were ready to pull the heads but the customer decided to not fix it at that point, but I spent quite a bit of time eliminating all other possibilities. Subarus have a penchant for cracking heads. I suspect the head was opening up a crack when it got warm, but I couldn't prove it without tearing it down, and I didn't get the chance.

[after oil]

the cap is 13 psi.

this from the ebay seller of water pump:

Hi Beck Arnley is the Reference numbers used. It is made in Japan but in a white box there is a N with a circle Around it as part of the casting. The old Vera Reference number is 57-01676 and superseeded to 57-02285 the picture is of the actual pump. Ebay wont let me revise it since ive sold one already. The other part number on the box is 21010-09W25. Hope this helps. Thanks

[philip]

that pressure test was done. it passed. still, it was the rad guy who did it, he still guessed head gasket. -SNIP-

The pressure test Al outlined above was NOT done; according to your posts. And now you mention your radiator fella's best guess was combustion gasses entering the coolant.

Denial ... ain't just a river in Egypt.

[after oil]

i missed that las post phillip, usually i get an email..
anyway...
the rad guy hooked up a device much like the one in the al's photo. it was connected to a compressor.

[after oil]

Denial ... ain't just a river in Egypt.

you are right... there is a Nile Creek on vancouver island.

so... how do i go about getting a new head for my rare and elusive?

from my flaps?