1991 Toyota Pickup Replaced radiator, etc - getting too hot

CALLEN1

MEMBER
1991 TOYOTA PICKUP

Engine Cooling problem
1991 Toyota Pickup 4 cyl Four Wheel Drive Manual 134k miles

I recently replaced a leaky heater hose, lower radiator hose, thermostat, and radiator. Things seem to be working fine now except my truck is doing two things that it did not do before: when it warms up, the temperature gets really hot, almost to the red, every time and then cools back down to normal. I assume the engine is warming up and then the thermostat is opening, but it did not used to get that hot and I'm worried that something is not working right. The other thing that is different is that when I first start it up, it is idling pretty high, at like 2200 rpms, and then once it warms up it idles around 1000. Again, this doesn't seem like a big issue but it didn't do that before so I want to make sure I didn't screw anything up. The only other thing I did while I replaced all that stuff was clean out the throttle body a little bit, but I wasn't able to get out much of the gunk in there. Does it sound like everything is OK or should I be worried about the high temp & high idle before things warm up?
Thanks.

4 Replies

MHPAUTOS

MECHANIC
31,938 POSTS

Hi there,

Thank you for the donation,

I would go and re check the thermostat, I feel that it is opening far to late, you may just have a defective new one.

Mark (mhpautos)

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Friday, April 23rd, 2010 AT 4:17 PM

KHLOW2008

MECHANIC
41,815 POSTS

Hi callen1,

Thank you for the donation.

The high idle is nothing serious to worry about but the high temperature reading is something that must be looked into immediately to avoid damage to the engine.

As the throttle body was cleaned, the air passage would be allow more air to get past the throttle plate and this would increase the idling speed. Tightening the idle screw slightly should get the idling speed down. Did you use carb cleaner to clean the throttle body? It is not possible to clean all the gunk without removing the throttle body but that is not really important. Getting the area around the throttle plate at closed position and the idle adjust screw air passage clean would be all that is required.

After repairs of the cooling system, was the system bled of air trapped? Symptoms indicates a possible shortage of coolant in system.

Recheck the coolant level in radiator and top up if it is low. Turn heater to maximum and with radiatro cap off, run engine and top up the coolant when level drops. Continue till the level maintains and close the radiator cap. Run engine till operating temperature and allow to cool down before rechecking coolant level again.