Weird engine temp spike issue

[thinmyster]

Okay so last night i was cruising down crowchild. Doing the speedlimit rpm ~2.5 when i looked down at my engine temp gauge and it was nearly at HOT 80-90%

So I immediately took my foot off the gas. (Eye on my temp gauge, and it drops almost as fast as me getting off the gas) back to normal operating temp!

Okay so i am like ??wtf keep driving for another 15-20 mins it spikes maybe once more and then gets really hot just as i am pulling into my gf's driveway.

What could this be from... Car ran normally the whole time besides this.

Other info: I have a Modified coolant neck that is vented into the engine bay with no reservoir tank. (In the process of doing something custom). I had to add maybe a L or more of coolant after i let the car cool down...

Is this just a case of low coolant? temp sensor in the water neck reading the temp of air rather than coolant? (i think there is a temp sensor in or near the coolant neck)

Car drove fine this morning but i definately didnt push it fearing this would happen again.

[suen17]

Sounds like head gasket. Hot combustion gasses making their way into your coolant -> temp spike? Reverse flow through same leak = coolant loss?

[mr2mike]

Bleed your coolant before you jump to headgasket issues.

Check oil for coolant too. It's a two way street if the headgasket is blown. Milky oil. You like chocolate milk don't you?

[Redlyne_mr2]

Mad air pockets in the mr2 bleed the system I'm doing mine Sunday if u want to roll by

[thinmyster]

i might take you up on that. Are you guys using the toyota "red" coolant?

[mr2mike]

Use the same as what's in your car. Mixing the Toyota Red and the other green stuff actually makes the coolant turn to gel. Or at least that's what I was told.

IF you switch, you need to flush it totally.

I've used Red and Green. Both are fine, never had an overheating problem.

[Redlyne_mr2]

Yah I only use the red, it's promotes the life of your waterpump.

[thinmyster]

okay thats what i have in my car now

[inline6turbo]

Yup you need to bleed the coolant. There's two bleed ports from the front to the back and you have to do it in order to make sure it's properly done.

[Redlyne_jr]

Yes there is actually 4 bleed spots on the entire system you only need 2.. or you can speed bleed it.. but this sounds like its the result of a poorly bled coolant system..

[mr2mike]

MR2's are special when it comes to bleeding. Follow the BGB and do it right. You can't cut corners on this system.

[willieboi]

If the temp gauge spikes, check if u have heat, good indication of have air in the system.

[Kloubek]

Could this not just be a sticking thermostat issue?