renenkel

Hello -- I'm new here...I'm the 2nd owner of a 1985 928S. I've had it for about 10 years and I love it and want to keep it going forever if I can :-) It currently has a problem that I hope you will be able to give me some advice on...

While driving on the highway, the traffic became stop-and-go for a few minutes, and I noticed some wisps of steam coming from the front of the hood. The temperature gauge was normal. The traffic picked up and I drove on, but kept an eye on the temperature. It started to climb just past the top white line (but not enough to make the red light come on), so I pulled over and shut off the engine. When I opened the hood, I saw that the bottom radiator hose had come off, and coolant was running out on to the road. I had the car towed home and examined it more closely.

The hose clamp had broken (it was a bit rusted). I thought, oh, that's all that happened. So I replaced the clamp, re-filled the coolant, and started the engine to test it. When it warmed up, to my surprise, steam started shooting out from the right (passenger) side of the radiator near the top.

Now that puzzled me. If all that happened on the road was that the clamp rusted and broke, leaking the coolant, isn't it just too much of a cooincidence that the side tank of the radiator also just happened to start leaking at the same time? Or if the steam leak happened first, why then did the clamp break and the hose blow off?

I've found some wonderful explanations (with pictures) here showing how to replace the side tank, but now I'm wondering, if I do it without understanding what happened, might it just happen again, or something else happen?

Could this have been some kind of overpressure situation? But wouldn't the expansion tank cap have released the pressure?

It never overheated before. The water pump failed a couple of years ago and I had it replaced.

I'm ashamed to say that the engine does have a rather messy oil leak which my mechanic says is coming from the head gasket on one side, but I've been putting off getting that fixed since it's so expensive and I can put up with the mess. But this got me thinking....could engine pressure have leaked into the cooling system, causing both the hose blow off and the side tank leak? I didn't see any obvious contamination of the coolant when it was leaking out onto the road...

Any ideas what might have happened? Or what I should check in order to find out?

Robert
Toronto, Canada
1985 928S (automatic, unfortunately :-)
1975 914
2002 Lexus (parts carrier for my other cars!)

JHowell37

Replace the end tank, put a new clamp on the lower hose if you haven't done so already. Fill it up and see what happens. I doubt that you have a leaking head gasket. It's probably a valve cover that's leaking and running down the head. If you haven't changed your thermostat or the expansion cap, it's probably time.

renenkel

Thanks JHowell37 for the comforting words about the head gasket. I feel better already :-) I've ordered a new end tank from 928 Int'l.

Unfortunately it's already started snowing up here, and the garage is taken up by my 914. I can just see myself, standing in the driveway knee-deep in snow (into which I keep dropping things), wrestling with the oil cooler nuts while "Jingle Bells" plays in the background....

I'll be sure to take some pictures so you can all have fun laughing at me :-)

Mrmerlin

if you saw steam coming from the top right side of the radiator I would venture a guess that you have a small crack in the end tank along the crimp. ( this would be where the top hose connects)
Otherwise the sudden loss of pressure may have caused an instantaneous release of pressure on the end tank seal and it has now resealed.

You can buy a new end tank and have it installed at a competent radiator shop.
Also given the condition of the car i would also suggest that you replace the heater control valve and the short hose that connects it to the head , if these parts are over 5 years old
(These parts are under the air cleaner housing connected to the rear of the right cylinder head).

Also inspect all of the hoses and clamps, any that are rusted should be replaced.

If the reservoir tank is old with cracks or tan or brown then replace it as well as the cap.


The oil leak is most likely one of the end cap seals leaking there are 3 per side, 1 in the front of each head and 2 in the back of each head.
This requires the valve covers to be removed if you do that then the valve covers should also be resealed,
new plug seals,8
new cam cover gaskets,2
and new securing bolt seals,26 IIRC
and use the loctite 574 to reseal the cam caps to head surface,
and Honda bond 4, to seal the notches where the cam cover gaskets go from head to cap

JHowell37

It's truly amazing. I remember back in the early 90s, you had to pay someone to haul away a rotting 914. And now, 928s sit outside so 914s can stay dry in the winter.

You just have to disconnect the lines using a 27mm on the lines, and a 32mm to counter hold the nut that secures the cooler to the end tank.

I'm assuming you saw the write up I did a few months back?

renenkel

Indeed I did, very nice tutorial, thanks for that. That's what convinced me I have a chance of success at this....
Hopfully I'll get some time to work on it over the holidays, and I'll be sure to post pictures of my struggles :-)