jeff48

Most of you guys know I am an oldtimer at rotaries but this one has me stumped. This is going to be a long post, but I am going to give you all the details I have.

I just had a more radical street port engine built and installed. I have the AST bypass modification (grafting a 2nd gen filler cap onto the OEM filler cap position) which has always worked well for me.

After a number of false starts the engine fired over and I took it out for a test drive.

I have three (yes 3) temp gauges, the stocker with the sensor at the OEM position near the oil filter, the Power FC commander with the stock sensor at the OEM position on the coolant neck, and an Intellitronix digital with the sensor mounted in the coolant neck just below the .9 bar cap.


Temps reported by all three gauges increased to around 210 F (99 C) going up the mountain but stabilized at about 85C 185 F tooling around town and up to 80 mph extended driving. After about 45 minutes I returned to the shop and burped the system which took about 8 oz of water. I then took the car out again but within 2 blocks, the aftermarket gauge started climbing into the 210s along with the Power FC going above 100, I flipped on the fan mod switch and immediately noticed the OEM gauge approaching the 3/4 hot mark (no warning light yet and not over the hot line). I shut it down and cooled off the system for about 1/2 hour. Checking the peak holds on my aftermarket gauge and Power FC it appeared that the temps reached 235F or around 112C. I opened the cap and added another 8 oz of coolant. I drove back to the shop where the car was again cooled and a few more oz of water were added.

My mechanic believed that the problem was because I have a stock radiator....we disagree strongly, since I have had the radiator in this car since day 1 and drove the hell out of the first engine with no negative results.

Long story short----I took my car as is and trailered it the 300 miles back to my house.

Here is where it gets weird. Testing the car in my driveway, I now notice that the PFC commander and the aftermarket gauge read similar temps (between 180F (85C) and 200F (95C)) but the OEM gauge is still going above normal. I would gladly believe the OEM sensor is screwed up, but I know these 3rd gens are much more tricky than that.


Finally, after warmup there are no bubbles appearing in the filler neck--- The system hold 14 psi with no leakdown as tested by a mityvac test kit.

I believe there is at least a possibility that I have an air pocket stuck near the OEM Gauge sensor at the back of the block and it is reading the high localized temps. I am open to other thoughts and all manner of cures that I should try.

Thanks
Jeff

P'cola FD

It sounds to me like you need to really burp the system. If you have coolant going to the TB, then pull the top hose off and add coolant until water comes out that hose. It has been my observation that air can hide out in all sorts of places in there, just to **** you off

P'cola FD

And don't let anyone convince you that it's your radiator. I've heard a lot of **** talked about the stock radiators, and in those people's defense, the stock radiator does suck ***. BUT, the stock radiator can cool a lot better than many think. I haven't gotten an upgraded radiator yet, not so much that I'm a cheap bastard (don't get me wrong, I'm a cheap bastard, but that's not why I haven't gotten the radiator), but because I haven't reached the limit of the stock radiator yet. In the summer time, in the deep south, while stuck in grid locked traffic, it has gotten to 215 degrees farenheit. Do I like that? No, but is that acceptable? Yes. One the car gets moving, the radiator does it's job better. It is definetly a good idea to get a good radiator, but I don't think that's your problem.

alwan16

other than air pockets another possibility is that the stock sensor is not working quite right. where did you get it? is it the old one off the old block? get a new one from mazda (reasonably priced) and try it. there's a simple test procedure in the manual too.

alex