23 replies to this topic

[masslaw]

Now I'm stumped. '96 Spi.  Did a 30km drive back from the lake averaging 100 to 120 KPH and when I got into the garage, there was steam coming out from under the bonnet.  I lifted it up and heard a "boiling" sound. So has it overheated?  A laser temp aimed at the head read 224 F.   (about 106 C). My dash temp gauge read normal.  My Smiths temp gauge, mounted separately, started out fine but later crept up to nearly the H.  I don't know if the aux fan kicked in as I would not hear it over the hum of the engine.  So:  water pump is new with less and 1000 miles on it.  Thermostat is 88 with a hole in it. Rad was flushed out and pronounced "good" by the rad guy. Possibilities:  Rad cap.  Thermostat,  Water pump belt tension. Dash temp gauge has failed. (It reads N throughout the trip.) I've used the proper sender from the thermostat housing to the Smiths and that gauge read H when the dash gauge read N. If I can find out what to do how do I test the dash gauge that comes from the manifold, i believe?  

[Quinlan minor]

Check the pressure cap and the hoses, first.
If the system is not pressurised, it will boil at “Normal” temperatures.

[masslaw]

There seem to be different caps for expansion tank and non-expansion.  My Spi doesn't have such a tank, just an overflow tube that voids to the ground, as far as I know,  Yet the cap on it now has two rubber seals which seem to be for the expansion tank models.  Confused

[Tornado99]

Could you see where steam was coming from? Any pressure loss will mean potential for boiling within the system, as it is the pressure that allows temps to raise well over 100 celcius without boiling.
A service shop can test a pressure cap for you if needed. Would also test the thermostat out of car in a pot of water on stove. I have seen new ones fail to open at rated temp.
You'll need to verify the cap is correct for a non-expansion tank setup if that's what you have.

[viz139]

A 96 Spi should have the expansion bottle under the wing, it should always be half  full of coolant.  Where are you taking the signal for you temperature  from?

[masslaw]

Taking the temp signal from the thermostat housing.  My mistake, I do have an expansion tank but it appears to be empty.  Coolant into the rad until some goes into the expansion tank?  

[brivinci]

The stock temp gauge gets its signal from a temp sensor in the intake manifold. If yours is clogged, it might not be giving you an accurate read. Happened to me (a long story) which is why I added a temp sensor in the traditional spot on the head, under the thermostat with the new head I installed that had the takeoff. 

[weef]

Reading through this thread it appears you are not addressing the main problem ie the engine is overheating, you will have to rectify this problem before worrying too much about temperature gauge readings. The temperature sensor bulbs are a "total immersion type" that is they have to be immersed in the coolant to give an accurate indication..They do not indicate accurately if it is only water vapour they are seeing. Sort out the overheating and go on from there.

[masslaw]

Perhaps fixed.  I replaced the stat, the rad, the rad cap, and all the hoses, and put in a new expansion tank (the old one poured coolant out onto the floor when I used a syringe to partially fill it.  I have been running about since the replacements and ,even on a long highway drive, everything is normal. The Smiths gauge reads a tad beyond the N and doesn't move. Thanks all for the suggestions.