22RE temp almost to the red, before coming down to mid way point.
 

I just had my timing chain;water pump replaced; thermostate (180 degree)and rad hoses. Runs very nice and actually has some pickup now (auto trans). The problem is that on the way home the temperature gauge got all the way up to the top mark (just before the red line). Then it went down to half way mark and stayed there for a while.

I thought it was an air bubble, so let it cool off and then started the truck without the rad cap on. Let it run till it got to operating temp and saw the steam comeing out of the cap (cool evening below zero), (still fluid above the ridges in the rad.. looking thru the rad cap). Reved the motor a little and turned on the heat, which was fine.
Put the cap on and took it for a spin (10 min city driving). Temp gauge stayed at the midway point, so thought it was solved.

Drove it this morning (minus 2 celcius this morning). And again the temp gauge got up to the top, just before the red and then went back down to the midway point. No pressure in the top rad hose.

Any reason for this fluctuation, I have read a few posts about this, and will try the elevating the front of the truck tonight will pouring in fluid. But the other posts, did not mention the temp coming back down on its own.

Any comments, help ..... would be appreciated.


cheers

Still could be a bubble by the t-stat but maybe the stat itself if sticking. What's your antifreeze / water ratio? Did you use the basic auto part store t-stat or a dual stage unit?

I used a standard 180 degree stat and the ratio of prestone to water was 65/35.

the temp does drop eventually, so the thermostat must be working, (but maybe only off the steam temperature, instead of water temp).

Again the upper rad hose does not have any resistance when squeezed while engine is running.

Some have problems with the temperature spiking after a cold start. Then it settles down and is fine. See http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

Would running the dual thermostate mentioned earlier, keep the temperature lower, once it reached operating temp. I think I have all the bubbles out of the system, but it seems like it is running hotter now than before (changing the timing chain, water pump, thermostate 180 degree, and rad hoses.

If it warms up beyond normal, then drops, that's a sign of a bad head gasket.

If your only overheating issue is a spike following a cold start, this t-stat issue may be the cause. If you're getting spikes at other times something else is going on.

A dual thermostat should run at the rated temp. They are just more responsive.

Drilling a small hole in a regular thermostat also works. Some get by with just taking the jiggler thing out so water can flow unobstructed through its hole.

^^^Mine has been going up to half on a cold start then it will drop back down to a quarter and stick there, I just figured it was the thermostat opening or the gauge/sending unit. It's been doing it for 3 months I hope it's not the head gasket.
I don't think the gauge spiking alone without the presence of other symptoms is a bad head gasket, I could be wrong though.

yikes!!! a friend of mine had a similar prob, until the car actually got hot, then the necessary parts would expand, and seal off the leak, where ever it was coming from, I told him, I bet it is the head/gasket. this is on a 4 cyl, chevy s10.

does this typically happen, after it has had a chance to cool down for a bit? say at least 30 minutes.

mine only does it on the first start of the day, after that it's fine. I haven't used any coolant in three months and there's no water/oil mixing so I just figured it was the thermostat or gauge

Resolution:

Jacking up the truck's front end and running it for about 45 min's seems to have resolved the issue of overheating.

temperature is still higher than before the timing chain and water pump replacement, but I think that might have something to do with changeing the engine timing. It was probably running without enough advance. It definately seems like it is quicker off the line and general acceleration.

Thanks for the input.