Temperature spikes?

[cdk348]

Hello. I'm having issues with my motor temp spiking 40 degrees or so in a few seconds and then back down to normal. I have noticed that some times the motor will heat up very quickly from cold but the temp keeps going up and never drops. During this occurring both hoses are full. This is my second thermostat and it still happening. I have a 350 with about 2k on it with a new radiator, new edelbrock water pump, new fan and fan clutch and new 160 deg thermostat.

[haysonj]

Originally Posted by cdk348

Hello. I'm having issues with my motor temp spiking 40 degrees or so in a few seconds and then back down to normal. I have noticed that some times the motor will heat up very quickly from cold but the temp keeps going up and never drops. During this occurring both hoses are full. This is my second thermostat and it still happening. I have a 350 with about 2k on it with a new radiator, new edelbrock water pump, new fan and fan clutch and new 160 deg thermostat.

Your thermostat is way too cold it should at least be 180, I run a 195 in mine but it is FI. You also can drill a 1/8 hole in the thermostat to even out the temps. Also make sure your bottom hose is not collapsing.You might also make sure you don't have a reverse rotation water pump

[chevy72blu]

Agreed on the T-stat, I didnt know they even made them that cool. You will get better MPG and the motor will run harder with a 195.

It sounds to me like you have air in the cooling system. Run it with the cap off and look for bubbles. Could be collapsed hose, as well.

[Daner]

I've had similar symptoms when an electric rad fan isn't working.

Edit: Missed that it's a real fan lol. Good Luck.

[cdk348]

The thermo I replaced was a 180 but with the issues im having I felt better for the time being to use the 160 until I get this temp spike issue figured out. I have never seen either of the hoses collapse during the spike. The coolant level is always constant and I have not had any boil overs or anything. I just hooked up a second temp gauge to the intake to verify the first one.

The pump is standard rotation as labeled.

[haysonj]

Originally Posted by cdk348

The thermo I replaced was a 180 but with the issues im having I felt better for the time being to use the 160 until I get this temp spike issue figured out. I have never seen either of the hoses collapse during the spike. The coolant level is always constant and I have not had any boil overs or anything. I just hooked up a second temp gauge to the intake to verify the first one.

The pump is standard rotation as labeled.

The 160 Tstat will open at 160 and will never close as the raditor cannot cool the water that much to close it. They use 160 Tstats in boats where you are using lake water to cool the engine

[cdk348]

What causes the hose to collapse anyway? I will put a 180 or 195 thermo back in when this temp spike issue gets sorted out.

[haysonj]

Originally Posted by cdk348

What causes the hose to collapse anyway? I will put a 180 or 195 thermo back in when this temp spike issue gets sorted out.

Some hoses do not have a spring in them and if the pump is pumping at full flow with the Tstat open the suction from the pump can collapse it

[buckskins4ever]

I have a question: When you had the 180 t-stat in, how long did the temp spike stay up? Small block 350 is a hot running engine and if you are using a 160 t-stat, you will almost always be in open loop.....and this will not allow the fan to draw enough heat out of the water.
Try this is you can: Take the fan and clutch off and install a Lincoln Mark 8 18" electric fan ($40-60 from salvage yard) and a Adjustable temp relay switch ($20-50) from most auto parts stores). Makes sure when wiring the fan power you do so that it is drawing air not pushing air.

[anglebinder]

Are you losing fluid? Could be air pocket in system, you could try filling the top rad hose (off the rad side)and reconnecting to rad. I had same problem when I had head gasket leak. A radiator shop should have a tail pipe sniffer that will detect any coolant burning and blowing out the tailpipe.

[cdk348]

I have not noticed any loss of fluid. The highest the temp with the 180 thermo in was about 230 during the spike. What concerns me is the speed at which it heated up to that point and the fact that there seemed to be no reason for it.

[haysonj]

Originally Posted by cdk348

I have not noticed any loss of fluid. The highest the temp with the 180 thermo in was about 230 during the spike. What concerns me is the speed at which it heated up to that point and the fact that there seemed to be no reason for it.

The only way that engine could spike that high is if the T-stat is not opening, are you sure you have it in right. The sensor tube and spring go in toward the engine.

[cdk348]

Yes the thermo is in correctly. My only other thought Is that my temp gauge is faulty. I will find out today now that I have a second one hooked up. I appreciate all the responses and will update when I figure out the issue.

[HSRACER]

Another great way to verify what is going on is to use an infrared heat gun that sends an infrared beam to what you point it at and returns that surfaces temperature. You can buy one for around 100 bucks. I point mine at the head, intake, radiator, hoses and water pump to see true temps all over the cooling system. That has shown me plenty of bad sending units or non opening thermostats in the past.

I also point it at each header tube when I think I have a miss to determine which cylinder is running cooler than the rest allowing me to pull the bad plug first.

Many good uses for this tool.
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[domeier]

I had the same deal when I bought my truck, 350, 190f thermostat and the gauge cycled between 190-230f. Drove me nuts until I figured out the PO had installed the temp gauge sender and temp light thermo switch in the wrong ports. The gauge sender should be on the left (driver's) side of the engine, temp switch on the right. If the gauge sender is in the pass. side port, you will see 230 at the top of the cycle.

PO's are all the spawn of Satan! Dude spliced the wire for the gauge sender to make it reach the passenger side port.

[cdk348]

With the new gauge installed at the intake the temp sits at 160 and occasionally will approach 180 during stops before returning to 160. The original gauge seems to jump around more radically and quickly then the other(occasionally momentarily showing 195 or so). Unless a 20 degree rise is irregular it appears as the gauge was the problem.

[bonnieclyde100]

if your engine is carbonated and has block mounted fuel pump , going up to 195 thermostat could cause pinging or vapor locking because of higher heat to carb and fuel line. these trucks came with 160 degree stats anyhow. fuel injected motors and carbed motors with electric pumps can handle 195 better. and will get better mpg

[Steeveedee]

Originally Posted by cdk348

With the new gauge installed at the intake the temp sits at 160 and occasionally will approach 180 during stops before returning to 160. The original gauge seems to jump around more radically and quickly then the other(occasionally momentarily showing 195 or so). Unless a 20 degree rise is irregular it appears as the gauge was the problem.

Same exact symptoms that my truck had last year. I hung a new gauge after replacing the thermostat (180 degrees), since it really didn't seem to be running that hot. The new gauge (Autometer Phantom) is manual, and is rock solid. It climbs maybe 20 degrees on a steep grade with the AC on (400 with a camper shell and all kinds of junk in the bed), or in extended idle in traffic. My gauge would peg at start-up. I first suspected the sender, but after replacing it, I got the same symptoms. In the end, it is probably the printed circuit going south. I'll probably end up putting in all new gauges, at some point.