Alabama Sam

I bought a new stock radiator from Lindsey Racing for my 1989 944 NA:

I had a retired Porsche mechanic install the radiator. He went through several venting procedures but could never get the car to run completely cool and the lower radiator hose never got hot, or even warm.

I brought the car home and started over. Put the car up on ramps. Drained some coolant, disconnected the upper radiator hose at the engine, poured coolant into the hose until it ran out of the venting valve on top of the engine. Put the hose back, put coolant in the expansion reservoir until it was above the max line.

Then I did this three times, so far: Started the car, drove it until it was getting hot (last white line before the red), put the front wheels up on ramps, let it cool, opened the venting valve and poured coolant into the little hole until it ran out. Close the venting valve. Repeat.

I’m making progress. Every time I cycle through the above drill the overheating problem gets better. I’m not there yet but I’m close. An hour ago I drove 20 miles before the gauge went up to the last white mark below the red mark, and its cooling down now getting ready for the next cycle.

Here’s the problem: The lower radiator hose still never gets hot. Not even warm.

This is a huge mystery to me. On here and the internet elsewhere there is talk of thermostats stuck shut and water pumps failing but I couldn’t drive 20 miles with either of those problems, could I?

I am not losing coolant from anywhere, not even from the reservoir's overflow and there is no water in my oil, or vice versa.

Thanks in advance for your help.

Lapkritis

Thermostat isn't opening. Replace it.

Alabama Sam

OK. I have resigned myself to doing that. One last question: When the thermostat is being installed is there any way that it can be damaged or bound up in some way so that it cannot open when being installed? (I've never done one before. My retired Porsche mechanic did the one that's in there now.)

I'm going to boil the new one before I install it, so I'll know its working.

TIA

thomasmryan

if your old thermostat tests ok you might inspect the water pump impeller.

austin944

Before trying to replace the thermostat (which is a PITA to replace), I would try bleeding the system by applying pressure into the system using a coolant pressure tester at the reservoir outlet, while opening the bleed screw. Do this several times with the engine warm enough to open the tstat, bleeding until you get no more air out of the bleed screw. If the coolant level drops significantly when you apply pressure then it means you still have trapped air in the system.

Alabama Sam

Reply to thomasmryan

I can't check the water pump without removing it, can I, or is it possible to inspect it just by removing the two piece plastic cover?

thomasmryan

it is a B to get all the air pockets out....lots of different methods.

be sure your system holds pressure including the cap before any parts are purchased.

the pressure tester works well for the initial purge. then, with the front raised and the engine warm, rev it to 2k momentarily and watch the bubbles rise up in the overflow tank when the throttle is released. when the bubbles stop, I hold the rpm a 1200 or so and crack the bleeder until I get a solid stream....multiple times to be sure.

if a new wahler thermostat does not resolve your problem, yes I would remove the water pump for inspection. if its good, it only costs the price of the gasket and your time. if its bad...well, consider it preventative maintenance and 4-5 hours of bonding time.

austin944

Look at Clark's Garage on how to check the WP while it's in the car:
http://www.clarks-garage.com/shop-manual/ts-02.htm

CG has a whole lot of information on diagnosing and repairing the cooling system. Also doing a search of the forums will yield a lot of information on this topic.

Lemming

Removing the thermostat is easy with the correct tool. Get a large pair of needle nose pliers with a 45o bend. Grind down the ends of the pliers to fit the clip holes. Rotate the clip for easy access and remove. Only takes a few minutes.

Alabama Sam

Thanks, Lemming.

Two days ago I ordered Snap On snap ring pliers, Part No. SRPC9045A, 45 degree bend, .09 tip, $33.00, plus shipping, which supposedly will save me from grinding. I got on the trail of that tool from the 944 blog Kevin Gross maintains at http://www.connact.com/~kgross/FAQ/944faq07.html, which has this entry at paragraph 7.03: Removing the 944 thermostat snap ring is extremely difficult due to its location and configuration. Ron Olsen has suggested a particular tool: Snap On PR5645A Snap Ring Pliers (45 degree with .09" tips)..

When I called Snap On I learned that the current part number for those pliers is the one I mention above. If they don't work its off to Ace Hardware and then back to the grinder.

Alabama Sam

Thanks, Austin.

In all my reading of Clark's Garage I managed to miss the section to which you referred me. That sounds doable, even with my marginal mechanic skills.

Alabama Sam

The next to last chapter.

Got the thermostat snap ring out tonight. Will be up and running with a new thermostat in a few days.

Here's a little more experience to add into the mix. You cannot get the snap ring out from the top. You have to get at it from underneath. I did not know that. Pull the radiator - it gives you more room to work. The Snap-On snap ring pliers I mentioned in an earlier post didn't work for me as designed, but after a couple of hours in frustration I put one of the plier points into just one of the snap ring holes, pried it a little, and that end popped out of the groove. It took only a little more time to tease the ring on out using one side of the pliers as a pry bar. Crude approach but it worked. The snap ring is a little bent but I have a new one.

Managed to score the water pump throat a little doing it that way, but I don't care. I'll dress it up with a stone before I install the new thermostat and snap ring.

I'll post one more time as soon as I'm successful in getting the lower radiator hose to get hot.

thomasmryan

Just out of curiosity, did you test your old thermostat that you removed?

Alabama Sam

Thomas Ryan: I'm going to do that, I just haven't done it yet. I will also test the new thermostat before I install it. Based on what I have read on this forum and elsewhere I am going to drill a 1/8th inch hole in the rim of the new thermostat, and I'll orient the hole at the top when I install it. This is believed by many to permit trapped air to escape upward to the vent and thus make venting the air from the system much easier. I'll report what happens. I hope to be up and having Cool Runnings by this weekend.

thomasmryan

if you old thermostat opens, I would pull the pump.

Mercedes puts a bleeder check valve vent in their stock thermostats.