Thermostat/CEL 52

[Buck Bridges]

Knock Sensor CEL 5-2

I come to you all for wisdom yet again...

I have a 95' 3.0 ATM, 151k miles w/ no service records, purchased a couple of months ago. Owner thought it might have a blown HG but after looking at it, the truck didn't seem to have any of the symptoms. Took it to my friend's shop and replaced the Valve Cover gasket, (had a significant oil leak) and we found that one of the fuel injector wires had been chewed on by a rat. Replaced the wires and that solved the low compression in C1. I'm driving it home with a smile on my face

While driving home on the highway, I notice the overdrive isn't working. I'm running at close to 4k rpm going about 65mph and tried to baby it for the 30 mile drive back home. Shortly before I pull into my driveway, I get a CEL error 72. After spending a few weeks on diagnosing the problem, I replace the EGR Temp Sensor and the light goes away! I drive with a smile on my face

Truck runs pretty good but OD still won't engage at higher speeds. I do mostly city driving so I put it on my list of things to do. The radiator is in pretty rough shape so figured I'd do a coolant pressure test at a local shop. Turns out, I'm leaking coolant from the Thermostat housing. I take a closer look and I spot the housing covered in a white crust. OK, so I order my parts, (thermostat and housing w/ gasket) and I wait for the weekend to put in the new parts.

Read on this forum about how some folks have OD problems being solved by replacing the thermostat. I start to get high hopes thinking I will stop the coolant leak AND fix the overdrive issue. I've noticed the truck runs SUPER cool and even 30 minutes of city driving doesn't raise the temp over 1/4 of the bar. Thinking thats odd.

I pull the housing off to discover there was no thermostat in place. It seems someone pulled it, (overheating issues?) and of course because there was no gasket, the darn thing was leaking. Installed the new Toyota OE thermostat and I'm pumped!! I look in the radiator before filling it and I see the picture below. It is brown sludge, a pretty thick coat too. I know some folks say it is from a HG failure but I've had almost no coolant leak, (except for the small thermostat housing leak) and my oil is super clean. No white smoke and no suction/vacuum from the exhaust. In fact, the coolant seemed to be dirty but there was no visible evidence of oix mixture, (aside from the brown sludge.)

I lost about 6lts of coolant while replacing the part so I put in a 50/50 mixture and fill it back up. I do the "burping" on a flat surface and end up pouring another 2lts back into the system. I'm smiling!

I hop in the truck to take it for a spin to see if the OD issue has been resolved. I immediately notice that the heater isn't blowing hot air. I get about 50 yards from the house and a new CEL comes on... Error code 52, (knock sensor) so I turn back home and shut off the engine. I notice that the temp is much higher now the thermostat has been installed.

There is no question the radiator needs to be replaced and I doubt the system has been flushed in a LONG time. I was planning on fixing the thermostat leak and taking it back for another pressure test.

So my questions....

1) Any idea what could have caused the CEL 52, minutes after replacing the coolant? Could air pockets in the engine be causing this? Any suggestions on a fix?

2) Does the brown sludge in the radiator mean I definitely have a HG issue or could that just be from years of buildup? Is it worth it to replace the radiator and have a full system flush if a HG issue might be looming?

3) Could the thermostat install have misaligned the ignition timing, causing the knock sensor fault?

I bow to your wisdom OH GREAT FORUM and I beg for your suggestions and Ideas.

 

[91'4bee]

I would either replace radiator/flush it and flush the whole cooling system first (including the heater core), bleed it well, you know that fun stuff. clear the codes and than drive it and see what happens. Good luck

 

[KidVermicious]

I've got $5 on air in the system after your drain and fill, which is why your heater isn't working. Air in the system will not cause your knock sensor code, but it's common for the knock sensor pigtail to go bad on 3.0 trucks, so that could be coincidence. It's absolutely worth it to have your radiator cleaned out and the cooling system flushed, bad HG or not. The brown sludge doesn't have to be oil residue, it could be from a previous owner mixing incompatible coolant types, I've heard that happens when you mix old school green or yellow coolant with Toyota red.

Don't replace the radiator if it doesn't need replacing - take it into a rad shop and have them pressure test it first. It might just need a good cleaning, which they can do for a couple bucks. You can have the rest of the cooling system professionally flushed, or you can do it yourself with a garden hose, it doesn't matter as long as you don't forget to backflush it and get all the crap out of the heater core too. Once your system is cleaned out and the radiator situation is squared away, you can refill with Toyota red, Zerex asian, or the new universal coolant, it doesn't really matter, but whatever you pick I'd stick with just in case. When you burp it, get the front of the truck as high as you can to minimize risk of air bubbles. When you think you're done, take it out and flog the throttle a little once it's at operating temp to shove any remaining air out of the lines and into the radiator, then bring it home and check the coolant level again.

I'd pursue the knock sensor code as a separate issue, at least for now. Rodent could have chewed on that too, and who knows what else. It might be a good idea to trace your entire engine bay harness, for that matter, just to make sure there's no new surprises. Good luck!

 

[Buck Bridges]

More clues

Thanks guys! I parked the truck on an incline and burped the system again and now I have heat pouring out of the vents. At least that problem is solved.

What I find odd is that my CEL is blinking at me, (5-2) within 20 feet of driving after installing the new thermostat. It seems too much of a coincidence for the knock sensor to just give out at that exact time.

Driving very poor now. Loss of power, idling is off, sluggish... I can't help but wonder if I installed the thermostat incorrectly because before the install, the truck was running very smooth.

Since the previous owner obviously took out the thermostat for a reason, I checked the rad hoses and both upper and lower are hot so it seems the thermostat & water pump are working correctly.

Going back to the shop today for another coolant pressure test and a professional flush if the radiator passes. Also going to get a diagnosis on the CEL and praying it is just the sensor. Fingers crossed

 

[Buck Bridges]

Update...

Just got back from the shop. After a diagnostics on the CEL 52, the report reads, "Knock sensor code found along with excessive resistance in knock sensor sub harness." There was not a detected knock, leading them to believe the sensor is bad. I do have a knock when I first start the cold engine but it goes away after about 1 minute.

I was quoted 4.5 hours to do the job @ $100/hr plus the parts, (knock sensor, sub harness and intake manifold gasket.)

Trying to weigh the pros and cons of doing it myself. I've never took on a job this big but I think its possible. Having just replaced the EGR Temp Sensor, it seems like all my sensors are failing, (knocking on wood... see the pun?!)

Just a thought, is is possible that i misaligned the timing by installing the thermostat housing? I took off two nuts, (directly above and below the housing) thinking that piece might come out for cleaning. I tried pulling on it a bit but it wouldn't budge so I put them back on went along with my project.

A video of what the engine sounds like at normal temp with the CEL on,

http://youtu.be/n1N0cLu5vMo

I'll search the forums and figure out the best plan of action. Any thoughts or suggestions are welcomed.

 

[Eacook1]

Don't our 4runners have an issue with the tranny coolers that are built into the radiators? I think I remember reading that sometimes they leak tranny fluid into the radiator or vice versa. Maybe that could be the sludge in the radiator. Since you said the tranny is not going into overdrive maybe it's got some contaminated fluid?

 

[Buck Bridges]

installing the new thermostat has brought my O/D back to life. My O/D issue was due to not having a thermostat installed in the truck. Previous owners took it out for some reason.

Thats a good point about the tranny fluid mixing with the coolant. Only way to know is to replace the radiator I suppose. Took it to a shop for a flush and they advised against it, saying it would be better to just replace the radiator. Too much gunk in there to save.

 

[91'4bee]

Yes defiantly get a new radiator. Ask the shop your going to, if you could buy a rebuilt metal radiator. That's what I did for mine. Paid 80 dollars for it instead of 180-200 dollars for a new plastic one. As for the knock sensor give it a try unless its your DD then I would go with a shop to replace that stuff.

 

[Buck Bridges]

Thanks 4bee. I've been looking online and I just don't want to switch to the newer plastic body radiator. Called a local shop and they quoted me $125 to refurbish my radiator... I might just do that. I have a hard time letting go of the brass radiator.