89 Classic running hot or is it?
 

I had a cracked cylinder liner in my stock motor, so had a 96 D1 motor w/ 100k on it swapped in. That motor was gone through by a Rover technician and has new head gaskets, heads were checked and are within tolerance. We also installed electric fans. I have a brand new radiator and tstat. The plugs all look good and there is no coolant loss, block tester kit shows no combustion has in cooling system. The Rover ran pretty good staying at 1/2 on the temp gauge, then started creeping up to 2/3 and 3/4 after a few days of driving. It's been sporadic though. Now, after idling for about 20 minutes the temp creeps up to right below Red and stays there. The top radiator hose is cold and soft when this happens, the radiator is warm, overflow tank warm/hot but not too hot to keep your hand on, and lower rad. hose is same.

I need help with what else to look at, my thoughts are:

Is it a bad temp gauge on the cluster, or bad temp sensor?
Is the tstat opening?
Could it be bad water pump?
Could there be a block somewhere in motor?
Should I install a mechanical temp gauge (if so what is best kind to use)?
Is an infa-red heat gun reading accurate enough to consider or a waste of time?

Thanks for any help.

Let's assume the following:

1. The gauge might be right. So don't run it until in the red.

2. Thermostat is like $10. Change it. 180F. Spring end goes inside the block. Little hole in flange or jiggle device goes at 12:00 position.

3. Use IR thermometer to measure in several spots and write down numbers when engine is cold and at various times when it warms up. The thermostat housing is a good spot.

4. Brand new radiator? As in copper/brass $$$$? A radiator that is clean inside will have temps from top to bottom on fins that is like within 10F.

5. Fans - do you still have a belt drive fan and clutch? If so, a paper towel should hold to grille, not be blown away at idle. Blade could be mounted reversed (cupped side goes toward block). Fan clutch when good feels like peanut butter inside, spin and relesease and it should turn less that 1 revolution.

If you have electric fans on the AC condenser, they should also blow toward block.

6. Sensor - The later block has two sensors, one for ECU (2 wire, square plug) and one for gauge (single wire, a little closer to stat opening than ECU sensor). If you need to, you can remove existing gauge sensor, attach a ground to it, and plop in a beer can 1/2 full of water. Put in a thermometer. Compare readings on dash gauge as you warm water in the can with a torch or can of sterno. Bad connection to sensor can make wierd readings even if you are not really hot. I'm assuming you don't have an OBDII port, or the GEMS ECU?

Also - you can check existing stat by removing it and placing it in a pot of water on the stove. And please check the belt route, don't want the water pump turning backwards.

Also - the 96 is a GEMS motor and the 89 was a Lucas motor from the ECU standpoint, and there are different sensors with different values. See the GEMS list in my signature, there is a smaller comparison of the various injection systems and components.

The gauge sensor in the 96 goes from 136 ohms (cold) to 17 ohms (hot). Values for cold and hot not given.

I could see the two coolant temp sensors being different values.

Savannah, thanks so much for all this info. I am in over my head.

The tstat is new but I don't believe they tested it first so we will test/replace that.

They converted to serp belt and no belt driven fan/clutch, just the electric fans. Also bypassed AC so no AC. Belt direction is correct.

Yes, the rad. is a new one that I got from PT - not a rebuilt original, but a new one. Plastic filler tank. Not sure who makes it.

I don't have OBDII and I don't believe they switched the ECU to the GEMS.

Given your 2nd post, that is what I had been thinking about - the different sensors feeding data to the old ECU, and causing a problem. In your opinion, is that more likely the culprit?

Thanks again for all your help

A temporary water temp gauge could be installed just under the hood for testing. Here is a pix of the intake area with stat removed. The coolant to ECU sensor is on the right, gauge sensor has the single wire. That "bolt" at the bottom is a plug for what used to be the hot water to heater core in older designs, and might be present on yours. A potential spot to plumb in a gauge sender. Of course, you might be using your old sensor with the old gauge, and in theory it should be working. In which case the temp range is scary.

This swap brings up another issue, the heater core. The GEMS setup had coolant always flowing thru the heater core. Older Rovers have a valve that switches off that coolant.

I'm not worried about the air flow at highway speed. But at idle you'll want to make sure the electric fans are keeping up. Mechanical to electric converions posted about on here have not produced the desired results usually.

Ok thanks. I'm always getting heat now it seems, so I wonder if the heater core is an issue. Heat pumps out even when it's not technically turned on.

I'll try a new tstat and an IR gun and then report back. Unfortunately it's not at my house so it's going to take me a little while.

By the way Savannah, I'll give you a great deal on this classic if you want it!