thermo stats

[steven.0424]

hi bought 86 navara cracked head put new head on installed thermostat top hose hot bottom cold ran without thermostat for first day stayed fairly cool was worried thermostat not going to open checked in cup with boiling water seems to open very slowly should i leave it out motor is sd25

[asavage]

Running without a thermostat long-term is a bad idea, as the clearances for all internal parts are designed for a specific operating temperature range.

Wild guess: are you certain that you have the correct replacement thermostat? It must have a lower blocker disc, as shown in the SD Thermostats Thread.

[steven.0424]

yes does have lower type termostat just worried seem to take forever to open temp gauge on quarter still not open cant see waer flowing across radiator cap when off with no thermostat it flows great

[asavage]

With no thermostat, some water recirculates via the non-blocked bypass port. You risk overheating under load, in addition to running way too cold most of the time.

[steven.0424]

yeah think it ok im just over cautious drove to work today with thermostat in when i got to work grabbed the temperature gun and pointed it on thermostat housing temp read 65 celcius so maybe it not getting hot enough to open fully maybe worring about nothing just didnt want to cook the head hard to get in australia and very expensive most are cracked one wreckers wanted 700 for second hand one could of got one new from china for that price ended up getting one second hand for 350

[asavage]

. . . just didnt want to cook the head hard to get in australia and very expensive most are cracked one wreckers wanted 700 for second hand one could of got one new from china for that price ended up getting one second hand for 350

Most SD25 heads are cracked?

We don't have a lot of SD25s here, but I've never heard of a cracked SD22 head. I wonder if it's like old MB heads, where some crack and some don't, on the same basic engine?

[steven.0424]

not sure what u mean mb head but yeah bought navara with supposive blown head gasket blowing heaps of white smoke no oil in water or water in oil when i pulled off head cleaned old gasket gunk off with sturdy six inch rule then remove carbon build up off head near numbers two and three cylinder when there it was crack from all four valves out wards bummer tried too get second hand one every body said they all crack common problem[got picture but cant insert it