I have a relatively newly acquired 99 SR5 3.4. The first thing that I did was run a block test kit on it and it came out fine. I then started baselining it. Changed all of the fluids and flushed the cooling system. It had green so I flushed the radiator, heater core and block with clean water and prestone flush. Then ran straight water through it 4 or 5 times that afternoon.

Lastly I did a 50/50 mix of distilled water and OEM red Toyota coolant. It runs fine and temps hover between 175 and 185. I plan on doing the TB, WP, Thermostat, radiator and hoses over the summer. Should I do a fan and clutch as well? Do those ever fail out of the blue.

I just wanted to see if there was anything else that I could do to prevent any head gasket issues that apparently come up from time to time on these motors?

On a side note, I just ordered LBJ and the 8 bolts from an online Toyota dealer so will be doing those next weekend as well. any help would be appreciated. Thanks

A scangauge or ultragauge to monitor coolant temps accurately would be a good idea. The factory gauge on the cluster is horrifically inaccurate and basically will only tell you that there is an overheating problem when it's too late.

This is purely anecdotal, but I think all you can really do is change your coolant at the recommended intervals (with the recommended coolant of course), keep up with cooling system maintenance, and monitor your engine temperatures closely. I think the Ultragauge has an alarm function so that’s a cool option. Real-time monitoring is a huge plus. It seems like you’ve already got that covered.

You can set parameters on a Ultragauge. It will sound a small sound alarm if the set parameters are breached.

Cool, thanks for the replies. I use the torque app now but plan to get an ultragauge soon.
Should a 99 sr5 be able to read the trans temp on those?
I know that there is much debate which programming works to get the pid to read right.

If you flushed it with water and then added 50/50 mix it is likely there was water left in the block, heater cores and other locations and may have diluted your 50/50mix, rad fluid testers are cheap and will confirm you got the correct ratio. The Toyota red long life should be a longer lasting fluid, but again it wasn't a thing till 99-2000 and then added to the Toyota manual for 01-02 so either will work.

I haven't heard much about HG failures on this motor - certainly not like the 2nd Gen V6. Overheating is your only real enemy and 175-185 is quite low as I believe we have 180 degree TStats. If you do the TStat, remember to locate the jiggle-valve at 6 0'clock. Doing so can produce a 10+ degree drop on this motor in these trucks.

OP also asked about your LBJ's, if you have not you should watch mtbtm video on it. Also up here O rielleys had the loaner tools that timmy recoends for popping off the lower ball joint and the OTRE's and without damage to the boots. Sure can be done without, but with the free to use tools, why not to prevent damage to the OTRE if its re-usable
Oh, you might find you need OTRE's or sway bar links and of course an alignment after.

Other wise you have good advice from others on cooling , and a tester is not expensive, up here we run at least 60/40 mix and I use the full strenth, not pre dillute, and mix to what I need to get me to -40 protection.
Do you need a fan clutch ? easy to replace later, but I would look at your fan bracket and bearing, its a sealed bearing and I had one start making noise at about 185k. I went Asian of course. And its located behind all the other belts so a good time to do when all the drive belts are off. Another bearing to consider is the ac idler pulley, but for me I dont need the ac so just took off the belt so dont need the pulley and it does not get hot enough up here to warrant its year round drag.

I had a very old OEM thermostat that was running the motor down in the 180-182*F range most of the time - a brand new OEM brought it back up to 188-191*F. As long as he gets a new OEM thermostat and installs it with the jiggle valve down, the temp he is running now won't cause any problems. It just lets you know the thermostat is old and 'tired'.

He's on the right track.

There were some head gasket issues on the very early 5vz's, but they had it figured out by 99. Most of the head gasket issues on the 98+ 5vz's are likely caused by poor cooling system maintenance. Same with many of the pink milkshake issues...

-Charlie

It seems like every once in a while you hear about a head gasket failure on the 3.4, unlike the 3.0 that is notorious for the issue. Maybe that's the engine you're thinking of?