so my 97 D1 with 108k started the dreaded coolant leak from back of heads but still ran great,used k-seal,let it cook,drained and flushed,changed t-stat and hoses.pressure was building and split expansion tank at seam [was about 4yrs old].put new exp tank in and just rented a engine block tester,used the exp tank to put the tube in and squeezed ball for minutes [level was below cross] did it until t-stat opened and began to fill tank,fluid stayed blue!! did i do test properly or should i have used rad hole? since tank was low when i started and began to fill i figured i would get gases also if they were there.when i put cap [new] back on level sank back down so i might have some air in there but more concerned with getting an accurate reading on tester.appreciate any imput [truck runs between the 8 and 9 pos on gauge]and doesn't get hot

 

It is supposed to go in the coolant tank, on any vehicle.
Any exhaust gas is definately circulating through there, after the thermostat has opened.
I'm not familiar with the D1 engine, but the coolant leak could possibly have been externally only.
And your fix has bought you some time.
If it's not leaking, steaming, or overheating, drive it, not much else you can do.

 

In coolant tank, 04 D2

 

thanks,wasn't sure,all the videos were putting tester in rad but lr have such a small fill hole,so if there's excess pressure it must be air in system right?i do hear the waterfall in passenger footwell,i'll do a couple more tests but if i bought some time i'm happy.thought maybe if air is in there it wouldn't give correct reading [by changing color]my concern was because the tank cracked at seam there must be too much pressure in system and i figured it must be exhaust gas,where else can you check?

 

Was the old expansion tank black? Is the new one white/clear? Have you checked the fan clutch yet? Checked the water pump bearing for wear? Even with the old tanks if it split the seam it's too much pressure, your either overheating or it's exhaust gas, probably overheating because of the head gasket(s) failing at the rear water jackets..... I'd still replace the head gaskets, K-Seal aint all that, can't protect against overheats and these engines need a solid working cooling system or else they'll find the nearest weakness.

 

thanks,old tank was white,new tank is white,viscous fan is new as is water pump,truck isn't overheating, gauge shows south of 9 o'clock position,rad is maybe 3yrs old,new ac fans [aftermarket that run even with ac off] since i hear waterfall at the passenger kick panel i thought might be trapped air,first block test shows no exhaust gas in coolant [but will do it again] i know head gaskets are inevitable but engine sure isn't showing me it's that time [and runs great]

 

K-D works well. Have used it many times on old girl lifts. Even used it in '92 Oldsmobile 3.8. But if it was my daily driver I'd think twice.

 

thanks,it is my daily driver but i don't put many miles on her,h-ll i'm hoping she'll give me 25k more miles before tackling hg,figure since i'm driving in s.fl heat and traffic if she doesn't overheat now maybe i'll get lucky and buy some time,[hope i did everything right by flushing crap out and changing hoses and t-stat,although i did put a oe 190degree in]

 

coolant leak could be just a valley pan gasket. debatable whether it is worth the effort to go down to the head gaskets or not.

 

thanks,just did second block test from cold to temp and fluid still is blue so i guess the process worked [at least for now] i guess the real test will be if it blows another exp tank or hose or gasket in the head,but as i said if it doesn't do it now in this heat it should last.still have to deal with waterfall at passenger footwell [whats wierd is the sound is right at the kick panel where your right foot would be