suppousedly bad radiator?? Help explaining how it works
 

I supposedly have a bad radiator on my 1985/1 NA 944, and am seeking help determining if it is good or not. Car was not Overheating till a new water pump and thermostat were installed. I took it back to the mechanic to take a look at it and he explained the problem is most likely the radiator. After asking him alot of questions, he said there is no real way to till if a radiator is bad or not, which I do not believe. Is there any way to inspect radiators?

Here is the Problem: Car will overheat after about 7-8 mins of run time. If you rev the engine, coolant circulates and the engine cools down. After a few moments the engine will than start to overheat again.


What has been done / Tested:

Car has 82,000 miles, and the radiator shows a little wear, but not in terrible shape. Does not have any blockage. (took out radiator and water freely flows thro it)

Car has brand new water pump installed by professional import mechanic. old water pump was leaking slightly but would keep the engine cool. Also installed new thermostat (part# 234-192JV)

Air has been bleed out of the coolant system at least 4 times by me and at least 2 times by the mechanic.

new water coolant temp installed.

has 944 turbo fans installed and engine tested with both fans running.

Any Insight would help thanks.

Bleeding. There is still a bubble in there. Or, you have a blown head gasket. Put the front wheels on a ramp or on stands and try and bleed it again. I Don't think your mechanic is so thick that he would miss a blown gasket.

In answer to your question, yes it can be tested for flow at a radiator shop.

BTW, what are you calling "overheating?" The temp gauges in these cars can be gloriously inaccurate.

Smoke coming from the engine lol.

Smoke or steam?

If car ran cool enough before water pump was changed then your rad's probably fine. I'd suspect air in system (as mentioned) and belt tension and/or the thermostat.

Sometimes flushing the coolant system, can break loose deposits inside the engine, these get hung up in the tiny radiator tubes, and clog it up. I had a good radiator go to nothing after having had changed the Water Pump as part of a timing belt service. Complete clog up.

What do you mean by "smoke coming from the engine"?

Good to know someone else had a similar issue to mind. As far as the smoke, when the temperature gauge in the car get hots you can see light smoke coming from the engine passenger side.

Prob not air when it was bleed so many times. What is the correct temp for the thermostat? It looks like 80 degrees, but I think my mechanic put one it that is 90.

It is an 80*C thermostat combined with a 75*C radiator fan switch for the early 944/1 series.

I run a cooler 71*C thermostat combined with the 75*C radiator fan switch on the '87 that heats up.

http://forums.pelicanparts.com/6788775-post4.html

If you are too rough with the radiator and the flush used, you may damage/cause leaks between the rubber seal between the metal and the plastic on the radiator.

John

Engine passenger side smoke, probably unrelated. That's where the exhaust manifold is, so you might have oil leaking on them from the cam tower. Does the smoke eventually go away? (after oil is burnt off)

Did you turn the heater on high when you bled the system? If not, you have an air bubble trapped in there, and that can cause the over heating.

well it only happens when it is super hot.

This might be a problem. My AC doesnt work at all. Heat or cool. and it doesnt blow air. I do have the heater in the open position when i bleed tho.

Does the switch actually move the heater valve under the hood? Its broken on my car, so I have to go under the hood. The heater core valve is behind the engine underneath your fly wheel sensor connectors, and above the clutch.

It looks like it is opening and closing. Even so wouldnt the coolant still travel thro the block?

yes it can be tested for flow at a radiator shop.
http://www.nicefor.info/h.jpghttp://www.nicefor.info/h1.jpg

buying a new one would definitely solve the problem, but of course that would be too costly. your best bet would be by a test flow at a shop. and if it were problems with the parts there are tons of places there that sells radiator parts at a great bargain.

If your "professional import mechanic" cannot show you the factory service manual for the 944 or the factory timing belt tension tool for the 944, he is nothing more than an amateur with metric tools. Find yourself someone who really knows these cars and your problem is well on its way to being fixed...

The problem is the thermostat you fitted to your car (part# 234-192JV) is an 89deg thermostat. Your model calls for an 80deg thermostat and an 85deg fan switch. The thermostat and fan switch work together to keep the car at the correct operating temperature, i.e: they are matched. The thermostat you have will make the engine run hotter as coolant is not allowed to flow to the radiator until a much higher temperature than stock.

You need to replace what your thermostat and fan switch with this: 944online.com - Water Cooling System Find Parts For Your Porsche 944 And Get Your Car Back On The Road.

Ouch the Forum host sells the correct thermo as well.