Overheat coolant - SD25 D21 1987 Nissan

#16

WHAT is goin on here?

this morning i started her up. everything warmed but the rad. as it warmed the fluid worked its way back out of the rad to the res and then out the res!

i guess im using alot of real estate here lately

#17

Have you read the "Thermostats" thread, and this post, where the correct and incorrect thermostats are illustrated?

#18

if memory serves me(i had the thermostat out on Sunday) i have the correct one.

i have been driving in all weather for 18 months, and this problem just surfaced. the posts you linked me to suggested that the wrong thermostat could cause a problem in hot weather.

is it possible that the water pump works only intermittenly?

#19

here we go again!

tried again this afternoon, the resi was full, and bubbling gasses.
i fooled around with the various hoses, blew in some holes, crimped a line to try to blow out another. after a little while everything is fine again!
i drove 8km, still good. the rad is not hot, its not cold, but there are some inconsistencies in spots.

#20

still no good!

it has been suggested to me that thermostats can sometimes work intermitantly . and perhaps that is my problem. what do you guys think?

phillip do you have a part number for the correct thermostat with the bypass port closer?

#21

I don't have the part number, but my local Napa store had the correct one. If this does not fix the problem, perhaps you should disconnect the veg-heater in order to eliminate possible problem areas.

It sound like your radiator is partially plugged (cold spots).

#22

perhaps you should disconnect the veg-heater in order to eliminate possible problem areas.

i did that when trying different things. but considering that it was fine in all weather for 6 months, now suddenly not, i tend to think its not that

#23

after oil wrote:it has been suggested to me that thermostats can sometimes work intermitantly

Not in my experience. They fail open (common). They fail closed (less common).

Do you have a part number for the correct thermostat with the bypass port closer?

I have updated Philip's excellent photo tutorial with NAPA part Nos.

#24

what if i just take the thermostat out? the weather has been pretty mild lately. is there a problem driving around w/o a thermostat?

#25

If you remove the thermostat, the bypass port at the bottom never closes: overheats.

That's why you need the correct thermostat with that disk on the bottom: it blocks off the bypass port as it opens, forcing water to not bypass the radiator.

#26

i got the new stat and rad cap yesterday and installed it. a couple of things happened. first of all it worked! everything seems perfectly fine now.
its a little embarrassing i guess that i wasted everybody's time with something so simple. but i figured the rad specialist would have told me to do that.
second of all, i got the hotter thermostat (190ºF), the temp gauge went another eighth or so past the centre, where it used to always sit. and as a result of being a little hotter, the SVO system's glow plug's thermostat tripped for the first time, turning off the glow plug. that is how my SVO system is supposed to work. it never turned off before. supposedly the glow plug is like a "bell and whistle" on this system. and we theorize its there to complicate things so people will hire the inventor of the system to install it.

ok, so we dont know if the thermostat or the rad cap was the problem. but before whenever i opened the cap, the fluid under pressure would spray out, hot or cold. now when i open the thermostat, the pressure, in gas moslty is directed to the resevoir.

#27

after oil wrote:i got the new stat and rad cap yesterday and installed it. a couple of things happened. first of all it worked! everything seems perfectly fine now.

Time will tell.

#28

Time will tell.

the wife drove the truck to work yesterday. she said on the way home the fans blew cold air for the first 6 or 7km. the drive is 15km. she said it ran fine on vegetable oil.

this morning i looked under the hood and discovered that the resevoir was full but the rad was low.

the wife drove the other vee to work today so i have the truck to fooll around w/ it.

any suggestions?

#29

after oil wrote:
Time will tell.
-SNIP- This morning i looked under the hood and discovered that the resevoir was full but the rad was low.

The wife drove the other vee to work today so i have the truck to fool around w/ it.

Any suggestions?

(ROFLOL) Get the whole system warmed up. Disconnect and plug off both coolant lines feeding the SVO warming system. Fill and purge air from the engine and heater. Go for a long drive. Stop on occasion an make physical checks ... radiator cold spots, hot/cold hoses when all should be the same temperature, recurring gases displacing coolant, etc. When the engine is hot, do you see coolant circulation in the radiator when you rev the engine? Do the basics.

#30

Today's update

Get the whole system warmed up. Disconnect and plug off both coolant lines feeding the SVO warming system

Done

Fill and purge air from the engine and heater.

Not sure how to purge air per se, but i watched inside the rad till the fluid started to fill it back up. first there was gasses, then foam and maybe a spec of dirt or two. then flow of fluid.i put the cap on, ran it for a minute, shut it down, opened it, started it up. this time the rad filled and bubbled, but didnt really over flow, it mainly just bubbled.

Go for a long drive. Stop on occasion an make physical checks ... radiator cold spots, hot/cold hoses when all should be the same temperature,

The hoses all seemed proper, very hot to the touch. the rad is cold near the top, warm elsewhere. I stopped and turned the rad cap to release pressure and lots of bubbles were sent to the resi.

recurring gases displacing coolant

How can i check this? i remind you that the rad specialist tested for combustion gasses coming from the rad with a colour/fluid test

do you see coolant circulation in the radiator when you rev the engine?

Is that answered here?

NissanDiesel Forums

Overheat coolant - SD25 D21 1987 Nissan

Who is online