Overheating diagnoses - loss of power HELP request! (1 Viewer)

[mudgudgeon]

Personally, i don't see water pump as a likely issue.
The only real way they can fail is a siezed bearing, or a leaking seal.
A siezed bearing would cause belts to make noise, or snap if it totally siezed.

 

[weaponoffreedom]

Personally, i don't see water pump as a likely issue.
The only real way they can fail is a siezed bearing, or a leaking seal.
A siezed bearing would cause belts to make noise, or snap if it totally siezed.

impeller might be gone who knows. It might be moving more water at lower rpms if there is an issue with the impeller. Maybe causing a void (bubbles) which would be undetectable, and adding to heat non transference.

I had a real problem bleeding my LX570 after doing the valley leak repair. The no leak radiator funnel was the key, that and blipping the throttle.

 

[weaponoffreedom]

Update:

Replaced the thermostat, it idles fine but maintaining RPM around 4k for over 20 seconds and the coolant temp climbs past 220°; so issue is still unresolved.

Can the fan clutch lockup at temp but still be faulty? I noticed that it did not “roar” on a cold startup.

The fan should engage after a certain temp, not sure what it is, but it should be engaging for sure. You might be on to something there. Be sure to bleed the system out very well.

 

[sbman]

I have a 'modded' blue hub fan clutch and I can clearly hear when it engages the fan, even driving down the highway or up an incline. I've never had the A/C cut out even after climbing local mountains up a steep incline for miles, but I do hear the fan engage intermittently during such climbs if I pay attention. If you aren't hearing your fan, it likely isn't doing enough.

 

[lumbee1]

My headgasket blew earlier this year. I had to drive it 30 miles home with coolant pouring into cylinder 6. It wasn't pretty. I was able to keep the engine cool by revving it. The only time it would spike was when I came to a stop. Even then, I revved the engine in Neutral until I could get moving again and cool things off.

I've got a Denso rad, blue fan hub, Toyota red, OEM Tstat, and OEM rad cap. Revving the engine should circulate the water but you need air blowing across the rad to cool it down.

 

[Gascan]

Update - And new OEM fan clutch did not fix the issue. Double whammy . I found this:

Bottom hose was blown off from both ends, hole burned through it and then one of the barbs broke as I disconnected it. Not sure if related to the overheat/power loss issue.


Anyone have the correct part number for this Exhaust Gas Recirculation (EGR) Vacuum Modulator? I seem to be getting different numbers compared to what's on the original unit.

 

[weaponoffreedom]

Update - And new OEM fan clutch did not fix the issue. Double whammy . I found this:

View attachment 3729388View attachment 3729389


Bottom hose was blown off from both ends, hole burned through it and then one of the barbs broke as I disconnected it. Not sure if related to the overheat/power loss issue.


Anyone have the correct part number for this Exhaust Gas Recirculation (EGR) Vacuum Modulator? I seem to be getting different numbers compared to what's on the original unit.

did you check the coolant for exhaust gasses?

 

[sbman]

Looks to me like you will need a new EGR valve as well, it shouldn't be porting that much heat back into the modulator.

 

[Gascan]

did you check the coolant for exhaust gasses?

No. There is zero evidence of coolant loss.

 

[weaponoffreedom]

No. There is zero evidence of coolant loss.

yeah you might not have coolant loss with a blown head gasket. It would rule it out 100%

 

[Gascan]

yeah you might not have coolant loss with a blown head gasket. It would rule it out 100%

How?

 

[weaponoffreedom]

How?

The pressure exerted on the gasket is much stronger on the combustion side. Bubbles in the system will not show through a look in the radiator, you need a no leak funnel for that at least.

Bubbles in the coolant could be forming a void in the system, adding to the overheating condition. Those bubbles would eventually manifest in the overflow tank.

You either have a blown head gasket, and bad water pump, and bad fan, or your gauge is not working correctly. It would eliminate the head gasket issue

 

[Gascan]

The pressure exerted on the gasket is much stronger on the combustion side. Bubbles in the system will not show through a look in the radiator, you need a no leak funnel for that at least.

Bubbles in the coolant could be forming a void in the system, adding to the overheating condition. Those bubbles would eventually manifest in the overflow tank.

You either have a blown head gasket, and bad water pump, and bad fan, or your gauge is not working correctly. It would eliminate the head gasket issue

While I agree that a coolant exhaust gas test has the final say so, what you describe manifests itself with an overflowing overflow tank that does not get sucked back into the system as it doesn't build/hold a vacuum with a seeping head gasket.

The original fan clutch and a brand new OEM fan clutch can't be both bad, so this is now ruled out by process of elimination.

The coolant temp is being read via OBD2 system, the overheating is - unfortunately for me - accurate.

The water pump may have failed, that's true, but MUD hive mind suggests that it would be very apparent; I'm not seeing any signs of that at this time.

The EGR valve may be a symptom of the issue or it maybe unrelated. A part of me suspects that a partially clogged cat might be the root cause; not allowing the engine to exhale the hot exhaust gasses at high RPM could lead to both overheating and what feels like slight powerless.


Sort of a side note, anyone know off hand if the EGR system can simply be deleted on an OBD2 truck same as an OBD1 truck (without a CEL)?

 

[weaponoffreedom]

he original fan clutch and a brand new OEM fan clutch can't be both bad

sure they can be

MUD hive mind suggests that it would be very apparent

hmmmm that has not help much so far huh?


EGR gasses decrease the combustion temps.

 

[sbman]

While I agree that a coolant exhaust gas test has the final say so, what you describe manifests itself with an overflowing overflow tank that does not get sucked back into the system as it doesn't build/hold a vacuum with a seeping head gasket.

The original fan clutch and a brand new OEM fan clutch can't be both bad, so this is now ruled out by process of elimination.

The coolant temp is being read via OBD2 system, the overheating is - unfortunately for me - accurate.

The water pump may have failed, that's true, but MUD hive mind suggests that it would be very apparent; I'm not seeing any signs of that at this time.

The EGR valve may be a symptom of the issue or it maybe unrelated. A part of me suspects that a partially clogged cat might be the root cause; not allowing the engine to exhale the hot exhaust gasses at high RPM could lead to both overheating and what feels like slight powerless.


Sort of a side note, anyone know off hand if the EGR system can simply be deleted on an OBD2 truck same as an OBD1 truck (without a CEL)?

No you will get a CEL if you just unplug/remove it. A fairly simple resistor mod or a more elegant relay/resistor mod is required if you want it to be gone with no CEL.

 

[Gascan]

No you will get a CEL if you just unplug/remove it. A fairly simple resistor mod or a more elegant relay/resistor mod is required if you want it to be gone with no CEL.

Yeah, I realized that the resistor mod is why I didn't get a CEL when the EGR valve failed after I posted the question. Just read @OGBeno posts about EGR delete and have my answer about that.

 

[ppc]

I would start looking at the possibility of plugged cats.

 

[Gascan]

Update: Some closure for those who contributed and those who may read this thread when trying to diagnose a similar issue in the future.

To recap, the cruiser experience a drop in power, would overheat at higher RPM (roughly 3,000+ RPM) and the EGR valve hose blew off completely along with melting the EGR valve modulator. As stated earlier, a new OEM fan clutch did not fix the issue; neither did a new OEM thermostat. After scouring MUD, I came across 3 or 4 cruiser owners who experience a similar melted EGR failure and a drop in power; all of these owners confirmed that the issue turned out to be a clogged/bad/melted cat (catalytic converter - keyword for future searches). At this point, I'll also add that I have an under 10 minute commute to work and the engine eats a bit of oil, so it probably had little opportunity to regularly heat the cat properly for several years.

After addressing the upstream cat (which appeared to have at least 2 to 3 square inches of the honeycomb blocked) and EGR system, power came back to normal and the latest drive, consisting of at least an hour of slow street driving followed by approx 15 minutes of highway speed driving showed 192°f as the highest coolant temp (albeit, its only a cool 84°f - 78% humidity today). Haven't been able to drive much due to the hurricane that just passed but will continue to monitor coolant temp and update this thread if things change. The issue does appear resolved.

PS: Thanks to posts in this thread, I also sealed up my aftermarket radiator/fan shroud with foam, like it had originally, and am undoubtedly better off for it.