fraggle

After reading several threads where people have suggested to take some IR readings on motors to help troubleshoot overheating problems, I thought I'd take it a little further.

I haven't ran across any nice threads for reference of what I should see on a well running motor, so yesterday I decided to take some readings.

I used these points.

Car: 1987 S4 with 5 speed, flaps disabled, fresh rebuild, 75C thermostat, new seal behind the thermostat (had 117,000mi with dead headgaskets before the rebuild), sharkblades, C&R rad.



And got this data



Here's the plot in C.



.. and here's it in F.



Circled points are after a 60 mile drive. Gauge was running right in the middle. You can see where the thermostat opened after 10 minutes.

H2

Good post. It will be nice to establish some sort of baseline. Thanks for doing this.

Landseer

Thanks for these data points, they will be very useful.

Congrats on getting your engine and car back together, huge job

If you get an opportunity, though its a little work, sure would like a baseline temperature inside the interior console. Mine is so hot in there after driving that I'm afraid to mount the radio. Doesn't seem normal. Am running 84 cat exhaust on an 85 and worried about the setup now.

.

fraggle

Hope to get a few more sets of data here. I'm not completely convinced my hobby temp gauge and method is accurate, there may be a linear offset to the data.

I do know I compared a bunch of cars at Frenzy08 and mine was ther hottest of the bunch at these same points, so in relative terms my results are repeatable. This was about a week before it completely failed the compression test with 100psi in 5 and 7, 160 in 6 and 8, with 190 on the other bank.

dr bob

You'll probably want to add ambient temps to your log data.

fraggle

Ambient is at time zero. It was warm in my garage!

fraggle

City drive yesterday, ambient temps in mid 80's. After 20 minutes:

P2 = 202F
P3 = 175F

This sounds high... sigh

Bill Ball

That's looks cooler than my car runs. However, the real test is not just driving around even 60 miles. It's a long, relatively steep grade on a hot day. Add AC running to that and see what you get. My car will run down around the Tstat opening point until I challenge it with an increased load, then it really shoots up and the marginal capacity of the cooling system is revealed.

fraggle

I'll have to put the condenser back in and give that a shot. I pulled it to see if it was blocking air flow. Things seem to run about the same with or without it...

I "cal'd" my IR meter - within a degree or two - by pointing at the digital thermostat inside the house. 78F on the wall is ~ 78.7F on the meter. Close enough for this work I think.

6mil928

This is good info. Thanks.

fraggle

Note: on P3 make sure to measure the metal to the left of the hose (as circled), not the hose or the clamp. At least with my IR gun there was a 20F difference due to ???!?!?! (cheap gun??)

I'm using this because it fits in the glove box with all the other portable troubleshooting gear (DVM, relays, fuse chart, etc):

$25 + ship from TOWER HOBBIES. It is about the same size as a cigarette lighter.


http://www3.towerhobbies.com/cgi-bin...?&I=LG6085&P=1