@Discoidiot I had a similar issue when I first installed the inline, a big air pocket got trapped causing a rapid temp increase. I pulled the thermostat, closed everything up refilled the coolant and ran her up to confirm ok then drove for 40 minutes. After cool down I topped up put the thermostat back in and all was good.

 

Well I hate to say it but those overheat events might have been enough to damage the head gasket, too soon to tell. I would run it with no thermostat at least to the end of the summer.

 

Well, the plan for the valve cover gasket change will be a good time to check head gasket, etc.

Thanks all for the input!

 

Had to replace my water pump, put in a flowcool that @acg had on hand. In 30C / 86F at 65 mph,A/C on lo, the Disco ran pretty solidly at 186 to 188. Climbing a long slow twisty 6-7% grade at 20 to 30 mph got up to about 190ish after 10 minutes. Added A/C for the last 2 minutes that got me up to 194.

One thing I noticed is my fan only seems to lockup above about 2200 rpm, Hayden 2991, anyone know if this is normal? I was sure it sounded like an airplane even at idle above 190.

 

RG, thanks for the feedback. Hayden has very good detailed on-line specifications for their fan clutches. AIR, thermostatic fans only rely on temperature at the bi-metalic element. The specs detail temperature for lock-up and un-lock, and the percentages of shaft speed. Temps at the element depend on outside air temps, velocity, and radiator/coolant heat transfer efficiency.

Your temps look really solid! My 3.9L D1 runs unpressurized with a flowkooler pump, Prestone Long Life, genuine stock t-stat, standard duty Hayden clutch with stock fan, and an inexpensive two-row aftermarket radiator with similar temperature results. Good thing too, it's 102 F/ 39 C here today. Way too hot for this time in June.

 

Just wanted to give my first impressions. I got the kit installed today after realizing my worm clamps were too small and nothing's open on Sundays. I took it for a 30-minute drive after I was finished, so the preliminary results are positive. It is a sunny 22C (72F) day. Usually, the truck would run between 195-205F during the loop that I did, which included a small mountain journey and some short highway stints. Speed was either 50 kmph or 80 kmph (highway) today, the highest I saw was 190F for a brief second just after the top of the mountain. Mostly temps stayed around 183F. The highest temps I saw before were two years ago, headed into the mountains, at 210F. I will be doing that in about a month, so I will report back what I find after that. Also of note, probably having nothing to do with the mod, but it seemed to run a lot quieter than normal. The T in the old system had a lot of gunk in it, not sure if that could cause everything to work harder and be noisier.

 

I had an overheat yesterday, was sitting at idle and it got red. Once I drove off it was fine. I am sure it was an airflow thing, but being 90 degrees probably did not help. I wonder if my fan or fan switch failed. I dont recall hearing it go off.

The top radiator hose was rock hard, then collapsed once it cooled. I pulled out the thermostat and I ordered a new cap. I have not had an overheat event in years, since the install of the inline thermostat. I wonder if the thermostat went bad and did allow the pressure to equalize? When I opened the reservoir, it was empty, but then the fluid filled the tank back up when the vacuum equalized. Pretty sure its not air in the system, most everything is new. I replaced the head gaskets a few months ago.

Any other suggestions on things to check or replace?

 

First question, do you not run some sort of external gauge? That is a must with a D2 as red is just a signal you cooked the HG. As far as troubleshooting, start with removing the thermostat element completely and run the housing empty, see if it runs hot. If it does at idle, you have a fan issue. If it does not at idle but does at speed, you have a radiator issue. Also, you may want to rent Advance's cooling system pressure tester to see if you blew the HG, it should hold overnight. Finally, you might want to consider running an unpressuirzed system going forward. It greatly reduces the probability of a blown HG in an overheat situation https://extinctmotorsports.com/the-e...s-10-min-read/

 

Pulling the thermostat seems to have fixed it. I had removed the jiggle pin previously, but still managed to have the collapsed hose. Also the coolant tank cap has three rubber gaskets, mine had none, so I am not sure if that was part of the fix. But after several long drives, temps in the 80-90s, seems to be okay. I think i will leave it out until fall, until I start getting the low temp error.

I let it idle hoping to get it hot enough to trigger the fan, but never made it that hot.

Coolant level has been the same all week.

I got the Autozone cooling test kit and it does not appear to work with our tank. Only fits the non-threaded tanks. Ill have to find an Advance.

 

PM your original order number, I will send a replacement.