77 Fj40 overheating

[sggoat]

So I'm driving to school to pick up my grandson. Temp on the rig starts to climb way past where it normally runs(under first tick mark on the OEM cluster gauge). Get to the school and we let it sit for a while. Back in to drive home-temp climbs slowly to the second gauge tick by the time we get home. Check rad with a thermocouple sensor and see 224 deg F at the rad inlet and t-stat housing outlet. Leave the hood open and let it cool. Next day-same type of scenario.-This time I notice smoke/steam coming from the valve cover vent-immediate shut down. Into the shop(I think the head gasket has blown)--Turns out that assessment was correct --gasket blown and head is cracked in many-many places(machine shop indicates these cracks are not new-been there for years.
New SOR head replacement(plus I added headers during the down time)
After replacement, still had the overheat prob. but it was way less severe. Shop checked the rad temp and says the temp is normal--running at idle for a while, and after a short drive--198 at the Rad top(inlet) and 171 at the bottom outlet hose. My thermocouple meter measures 206 at the top and 185 at the bottom outlet. They said this was normal--The Cluster gauge temp indicates a little past mid scale(way hotter than it used to run). They checked the rad using a thermo gun, and said the rad was ok.---I do not believe any of this--the OEM gauge/sender was not molested(as far as I can tell) and should still read temp as it did before.
Does anyone have normal temp readings for this 77 Ca. 2F(desmogged) after driving at 45 MPH for approx. 30 minutes??

 

[JohnnyC]

How old is the radiator?

When mine started to head into the middle of the gauge I found my radiator wasn't as good as it used to be

 

[Solace in Solitude]

Does anyone have normal temp readings for this 77 Ca. 2F(desmogged) after driving at 45 MPH for approx. 30 minutes??

Sorry, Gary - I can't help you with the 'normal temps...', but is there a chance that air got into the coolant while the head was being replaced? Maybe burp it and see if that helps?

Otherwise, I think Johnny's question is the best starting point.

HTH

 

[thzpcs]

Seems like cleaning it would be the best thing to start off with. Rads get really filthy really fast.

 

[DougAustinTx]

My new radiator drops about 40 degrees from inlet to outlet temp. If you don't lose enough heat in the radiator, the engine will keep adding more heat and you're stuck in a vicious overheating circle. Also, make sure your fan clutch is tight and your shroud is properly in place.

 

[ozcrusier]

I agree the inside gets blocked with crud even if the outside looks good. Most radiator places will recondition a radiator by stripping both tanks cleaning the core soldering it back together for a few hundred bucks.

 

[DSRTRDR]

have you checked the fan clutch ? I have never measured temperatures, but I check the fan clutch when the gauge doesn't come down after passing the second peg

in the almost 10 years that I had aftermarket clutches on my 2F, they would quit every 2-3 years (I now have an Aisin, too little time to tell)

 

[Weber Sarge]

Without a mechanical gauge I'm not sure where exactly my engine runs as far as temp , but you have the same issues I had with climbing temps - took replacement of the radiator to cure it . I vote an OEM one , I did the whole Champion route and would not recommend doing it , fits ok but there are shortfalls like the drain location is off by 1" or so and the quality isn't Toyota for sure . It does the job fine , but I'd just rather do it right . The fan clutch really shows up in low speed runs around town and sometimes at high speeds on the highway . I'm considering trying to convert later to use the Tacoma/Tundra odd colored clutch or rebuild the stock unit as mine seems a bit sluggish to really engage when the engine is heating up . The one on my Taco does the old-fashioned diagnoses on startup - fan roars loudly for a few seconds then settles down , temp gauge even when towing heavy loads never moves - those work great .

As a side note - try backing the truck into a fairly steep ditch after filling the radiator , leave the cap off just after filling and tip it at least 30* with the rear down - seems to burp those rear heater lines perfectly .
Sarge

 

[cruisernerd]

Thermostat?

 

[sggoat]

I was down to the radiator or the water pump. Just installed a new pump today(SOR-OEM)-The old one shows severe washing out of the housing-but I still don't think it's so bad that it would cause what I'm seeing. The rad is a Champion all Alum rad-less than 3 years old, but I'm suspicious it's partially plugged. Fortunately, I kept the original radiator(it's in the shop now getting cleaned and rodded out)--should be finished by Wed. next week.
In the mean time, since I had to remove all the hoses, etc. to fit the new water pump, yanked the radiator and did the Cascade flush trick on it--1 cup Cascade dissolved in 1 gallon hot water-added to radiator as it was laying flat(this rad holds just about 1 gallon). I had some old, scavenged parts from a recent clothes washer we replaced--hooked up the pump/hoses so I could rev flush the rad to see if I could clean it up--flush rig works just fine--no discoloration as yet after ~ 1 hour of running--

 

[sggoat]

have you checked the fan clutch ? I have never measured temperatures, but I check the fan clutch when the gauge doesn't come down after passing the second peg

in the almost 10 years that I had aftermarket clutches on my 2F, they would quit every 2-3 years (I now have an Aisin, too little time to tell)

I am not sure how to check the clutch-what should I look for? - The current clutch rotates with some resistance with the engine off. When the engine is running, it seems to be moving a lot of air. The truck takes a long time to get to the high temp-if you drive it at ~ 30-40 mph, it seems to stay cool. I f you move up to 55 mph, the temp starts to steadly climb to the mid scale on the cluster. If you drop it back to idle(as in getting it home and letting it sit idling, with the hood open) the temp seems to peak and very, very slowly drop. Shutting the engine off and letting it cool for ~30 mins, then restarting, the temp drops back to the normal "less than the first tick mark" on the cluster gauge

 

[Weber Sarge]

One of the issues with fan clutches is just age - the thermo spring on the front is suppose to react to heat from the radiator and wind the vanes inside the clutch to a more "closed" position , this forces the fan to turn closer to belt speed instead of freewheeling . I'm considering rebuilding mine as it doesn't seem to hook up very solid on hot days running at high speeds , but the corrosion of that spring is hard to get past . Not sure if you can buy a new spring or not , the o-rings and other parts should be available including the viscous coupling fluid . I get from reading on the 80 board the Tacoma/Tundra odd colored clutch (almost pink) has a pretty aggressive lockup spring and is a heavy duty type to start with - looks to be the same bolt pattern too .

Biggest things to check is bearing play when hot/cold and see how much air it's moving at idle when hot - it should be pretty substantial . Your speed-dependent heating is usually associated with a radiator issue , what thermostat are you using ? Mine never worked quite right with the new rad until I went back to an oem thermostat - they just plain work a lot better . Since I installed a new radiator and the block had straight muddy-looking water in it I decided it best to run an upper hose filter to protect the new rad -

http://www.ganofilters.com/

There are some other maker's out there , pick a style you like . On my '77 we had to get creative with the upper hose to make it work since the outlet on the thermostat sits so close to the rad and that tight upper radius going into the upper neck .

It's amazing how much crud comes out of the block on these engines - age is the biggest culprit along with owners not changing antifreeze at regular intervals . I've had to clean that filter screen about 6 times now in the last year alone ...

Sarge

 

[sggoat]

Now this is an idea I like--I was thinking about something like this (at ~ 3 am)when I woke up, worrying about the cooling system situation.-Thanks for the post, i'm going to definitely check tis out

 

[sggoat]

Finished the rad flush--no appreciable dirt/debris came out that I could see. I opened up the t-stat housing to check the tstat rating and it is a Stant 180 deg. one.(this one was replaced immediately after the overheating started, but didn't change anything). All the parts are going back together tomorrow-new water pump/flushed rad/flushed block and head.
I read somewhere on the forum that timing might be a contributor to heat build-up(too far advanced or retarded)I don't have a timing light or dwell meter, so I'll have to get that checked on Wed, when I go get the OEM repaired rad.
If the truck gets hot on the drive there, I'll know the new water pump didn't fix it, and my attempt at cleaning the Al rad didn't work either. The only things left that I can think of is install the cleaned OEM rad to see if that solves it, plus make sure the timing is correct. if none of these work, the t-stat is coming out--I know this is a bad thing to do, but I would rather have the engine running too cool than too hot. If that works-points to a bad t-stat. MAybe I could find one that opens at a lower temp--maybe 160?

 

[Weber Sarge]

I went through several aftermarket thermostats in mine with the new radiator and none of them ran consistent . Finally just bought a new oem from toyotapartszone.com and it's worked fine ever since - lesson learned . I don't understand why aftermarket thermostats just don't seem to work on Japanese trucks , had the same exact issues with my old Sami and same results .

I'd get that timing checked , it can contribute to the problem for sure . More than likely that radiator is somewhat plugged or the fan clutch is not working properly . Is the thermo spring on the front very rusted ?
Sarge

 

[Steamer]

When you flushed the block did you get good flow out of the block drain? A lot of junk likes to settle there.

 

[sggoat]

Block flush was fairly clear(I did not see it personally, but the tech told me it was-he's an old school kind of guy, knows carbs pretty well-I think I trust what he said). I'm leaning more and more to what Weber Sarge says--non-oem may not be the best choice--I can't think of anything else in the cooling system that would cause this accept maybe the pump/rad/t-stat--the pump is new-I also blew some water through the block before I put the pump on--fairly clear there also-so if my rad flush worked, it should be out of the equation--only thing left is the t-stat(or possibly the fan clutch). Gonna run it with the installed stuff in the next day or two-if still get the overheat, gonna pull the t-stat and see if that drops the temp. If so---bingo! new OEM t-stat. If the truck still gets hot, I have the old fan clutch that was converted to direct drive-I'll put that in to see if it helps

 

[Weber Sarge]

I haven't done it yet , but look into the guys doing the swap for the 80 series using the pink clutch from late-model trucks . They are quite aggressive - have one in my Taco and it roars like mad when first started .
No t-stat will take forever to heat up , they do make a 160* aftermarket unit as I have used one last year solving my issues .
Sarge

 

[Steamer]

The reason I was pointing out the block drain is that I've read here in the past that a few folks were not aware that it was even there. (Me too). And a few more have had trouble getting it unclogged. (Me too). It's in the back, at the bottom of the water jacket and farthest from the water pump so the velocity of flow is low in that area. Crud in the system likes to settle there so opening or removing the drain valve can give an indication of the systems condition. I'd ask the mechanic if he had the valve open & flowing well. You could always just open it yourself and drain a cupful out to know for sure.
Also one thing I've learned from my crud clogged problems is that just because the water flows freely through the radiator or block doesn't necessarily mean it's clean. It can often mean that what's in there just aint lettin go.
I really like Sarge's filter. I didn't know they existed.

 

[Weber Sarge]

I had to remove the block drain and clean it out with a drill bit - it was corroded pretty good and blocked by rust debris - good catch as I almost forgot about that part . When the block was being flushed (garden hose inside the inner thermostat housing) I used hard wire to rod out the bottom of the block cooling channels the best I could reach them - lot of junk in there . The CLR , and later , Muratic acid did a pretty good job on it but I don't really recommend going that route unless you know what you're doing - you can destroy an engine .
I will say it's a really good idea to give these engines a solid flush yearly and change coolant out - just for long-term reliability .
Sarge