87 - 924'S' overheating its a tricky one

[KillerDynoSoar]

I just got a new 924 'S' and you guessed it its over heating.

Ok the first issue was the fuse was blown. Simple fix.

Then I found that the 2nd faster speed fan wasn't coming on. I just pulled the relay and pushed the relay back home firmly and .. bingo the faster speed came on a treat.

I let the car get hot and the fan came on a treat and cooled the engine down just fine.

I took the car for a drive and on the open road any speed above 50mph the engine cools just fine.

However if the car encounters traffic or slow speeds its over to the red area of the gauge.

If I stop at the lights the car cools back down.

???? what gives ????
Any ideas?


The expansion tank when opened and the car running is not bubbling or indicating a head gasket leak. There is no leaking around the head either.
The water doesn't leak.

The water pump isn't making any noises or leaking.

The thermo switch has been replaced by the previous owner. Its also been bled.

The top hose is hot and the bottom hose seems a little cooler but hot also.

[legion]

Maybe you have an partial obstruction in the radiator or a hose that allows for adequate cooling at speed?

[John_AZ]

I read a recent post and the problem turned out to be the thermostat. If you do decide to get dirty and replace the Tstat, get a pair of 90 degree snap ring pliers for the "C" clip. Get both rubber gaskets for thermostat and possible replace the waterpump to thermostat seal inside the waterpump. All this of course if you know when the last time the waterpump was replaced. You may just want to replace the WP as well. Then you will need to buy or borrow a flywheel lock to loosed the main crank pully to get at the WP after the sheilds are removed. Then as long as your up to your elbows in loose parts you could replace the front seals and look at the oil pump drive gear for wear. (The crank seal will grove the gear and oil will leak eventually) BUT, for now just replace the Tstat since its only a few pounds and messy.
I think you should just ponder all of this at JD Wetherspoons.

John_AZ
1988 924S
1987 924S

[nynor]

maybe the temp sender is bad, giving bad signal to the gauge.

[John_AZ]

Yes, and this all is based on the assumption that grounds, charging system, battery are OK and all of the recent rains and flooding in the UK have not corrupted the electrics. Good day.

John_AZ

[KillerDynoSoar]

Thanks for the advice buddy.

I have noticed that the pressure gauge always shows the needle right over to the extreame right. I think its a bad earth... so maybe a electric problem.

However I don't think so in this case.

I'll replace the thermostat as a matter of course. I'll call the previous owner and see if he had it changed recently, I know he had some work done at aPorche specialist. I'll also check the seals too. I had better get a Haynes for the procedure.

Can I inspect the waterpump at the same time? Just to check its ok without dismantling it?


PS: The 924 'S' is bloody awesome to drive! Wow!

[Techno Duck]

There is no way to really inspect the waterpump without taking the timing belt off. Best you can do is listen for strange noises.

May also try bleeding the cooling system of air. If work was recently done to the cooling system, its possible it was not bled correctly. And the 944/924S can sometimes be a pain to get air pockets out of. Get the front end on ramps or as high as possible in general, crank the heat and open the bleed valve at the upper radiator hose goose neck.

[924Sman]

I second the bleeding of air. Also make certain the cam belt tension is spot on, may be slipping on the waterpump pulley. Cool bottom hose suggests the thermostat is bad. When little or no opening(stat valve) the coolant remains in the block and not able to cool effectively. It appears you have a minor issue and the valve is not opening fully, holding some coolant back from reaching the radiator or visa versa.

Not to cause fear but the headgasket may still weep it is just that the coolant is evaporating or burning off in which may impede you seeing a live leak.

Dal

[John_AZ]

KillerDynoSoar,
If I read correctly, you also said your pressure guage pegs full right. If it does not lower when engine temp is normal operating temp there are a couple of solutions. 1) the oil pressure wires to the sender are reversed. 2) the oil pressure relief valve OPRV needs new seals and cleaning. 3)clean all your grounds. 4)the sender is bad-not cheap. 5)OR, how do they say this in the Queens language, DAM!
These are all typical. Enjoy the ride.
John_AZ

[KillerDynoSoar]

I was really hoping that changing the water pump wouldn’t such a major deal… but you chaps seem to suggest that I’ll need to remove the timing belt etc… which seems like a major pain.

I think I’ll replace the thermostat and flush the cooling system again and then fill her up again ensuring that I bleed the system properly.

I’ll also stock up on fuses and a spare fan relay.

Not sure if I want to be doing the water pump if it not required.

Thanks for the tip on sorting my Temp Gauge. When you say ‘grounds’ do you mean all the earthing straps in the engine bay.. or do you mean just the earth wires in coming from the gauge.

Thanks again.

Al

[John_AZ]

All the earthing points, about 7 on body front and rear. The one needed most is up above the fuse box. I would think it should be the same place for right hand drive. Crawl in front on your back with a torch and poke around up to the underside of dash. Most dash guages are earth strapped here. Clean the battery cables at both ends.
John_AZ

[Techno Duck]

[Slam]

This may seem obvious, but have a look at the A/C rad in front of the coolant rad. If the fins have been flattened then you won't get good air flow. It could just be that your rad is gunked up. I replaced mine a couple of years back with a good used one and that made a BIG difference.

[John_AZ]

TechnoDuck,

Thanks, I am corrected. KillerDynoSoar the earth I referred to is on the RHD 924S is by the passenger side up under the dash. I never knew the RHD 924S battery is in the rear hatch. Did they put the spare emergency tire someplace else or is it fitted together with the battery?
John_AZ

[HondaDustR]

Yes, change the thermostat for sure. It's a PITA to get the snap ring back in correctly in the groove. Also the inner seal is extremely hard to remove, unless someone knows something that I don't...

I have had problems with the thermofan switch not being activated (or slow to activate) if the cooling system has a lot of air in it. The easiest way I have found to fill the system is to dismount the coolant expansion tank so it can be held higher so gravity can force coolant in and air out. Once the engine is warm, just open the bleed screw while elevating the tank so that you get a positive flow of air and coolant out of the bleed screw. It gets the air out pretty fast without having to wait until the system is scorching hot. And make sure the heater valve is wide open so any air will be flushed out.

Flushing the system with radiator flush can help as well. I used the flush proceedure here and it helped.
http://www.pelicanparts.com/techarticles/944_TStat_replace/944_TStat_replace.htm

Some things to be aware of in that article: Don't use a lower temp thermostat, since the engine must run hot enough to boil off the water condensation that builds up in the crankcase after cool-down. Also, replace the thermostat with an OEM part like the ones sold here. I bought a Stant part from a local parts store and had poor cooling performance problems, probably because the diameter of the flow passage through the thermostat was noticably smaller than on the OEM Wahler part.

[KillerDynoSoar]

Hey guys, I'd like to thank you all for the great advice. I'm going collect the parts I need and then plan to do the work one morning next week.

I hope I nail the issue once and for all. I'll so check all the grounding straps to make sure my car is earthing properly.

These cars are unbelivable.